213
Epilepsy Res., 8 (1991) 213-219
Elsevier EPIRES 00391
Effects of chronic treatment with haloperidol and methamphetamine on hippocampal kindled seizures in the cat
Kenji Emori, Yoshio Minabe*, Yasuyuki Tanii and Masayoshi Kurachi Department of Neuropsychiatry,
Faculty of Medicine, Toyama Medical and Pharmaceutical University, Sugitani, Toyama (Japan)
(Received 28 June 1990; accepted 18 November 1990) Key words: Kindling; Amygdala; Hippocampus;
Haloperidol; Methamphetamine;
Cat
We assessed the effects of chronic treatment with haloperidol (O.S-2 mg/kg/day, p.o., 17 days) and methamphetamine (l-2 mg/kg/ day, p.o., 17 days; 4 mg/kg/day, p.o. 9 days) on hippocampal kindled seizures using a kindling procedure with low-frequency (about 3 Hz) electrical stimulation in cats. The number of stimulating pulses required to trigger epileptic afterdischarge (pulse-number threshold, PNT) was considered an indicator of seizure threshold. Haloperidol, 0.5 and 1.0 mg/kg, reduced the duration of epileptic afterdischarge (afterdischarge duration, ADD) without affecting PNT, and 2.0 mg/kg strongly reduced PNT and ADD. Methamphetamine, 2.0 mg/kg, reduced PNT and ADD, and 4.0 mg/kg preferentially reduced PNT. The effects of the two drugs on hippocampal kindled seizures were found to be partially opposite to those on amygdala kindled seizures, suggesting the different response of these limbic structures to dopamine receptor manipulation.
INTRODUCTION We have recently reported pharmacological studies using a kindling model of epilepsy induced with low-frequency electrical stimulations (2-3 Hz), referred to as the low-frequency kindling technique’8~‘9~20.In these studies, chronic effects of psychotropic drugs on seizures kindled from the * Present address: Department of Psychiatry and Behavioral Science, State University of New York at Stony Brook, Stony Brook, NY 11794-8790, U.S.A. Abbreviations: ADD, afterdischarge duration; AM, amygdala; MAP, methamphetamine; HPD, haloperidol; HP, hippocampus; PNT, pulse-number threshold. Correspondence to: Kenji Emori, Dept. of Neuropsychiatry, Faculty of Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-01, Japan.
0920-1211/91/$03.50 0 1991 Elsevier Science Publishers B.V.
2 limbic structures, amygdala and hippocampus, were evaluated. The low-frequency kindling technique has a great advantage3 in quantitatively and chronologically assessing the seizure threshold and the severity of induced seizure. The former was indicated by the number of stimulating pulses required to trigger seizures (pulse-number threshold, PNT), and the latter was indicated by the duration of epileptic afterdischarge on EEG record (afterdischarge duration, ADD) and the behavioral manifestations of induced seizures. Since a previous study showed that the effect of chronic lithium treatment on limbic seizures is dependent on the location of seizure origin*‘, we decided to study the chronic effect of haloperidol (HPD) and methamphetamine (MAP) on seizures generated from stimulation of the hippocampus (HP), and compare the data thus obtained with the results of
214
previous studies of amygdala (AM) kindled seizures18’19,which were done under the same conditions as this study. HPD is usually administered repetitively in clinical use and its antipsychotic efficacy requires at least l-2 weeks of continuous medication2. HPD is known to have a proconvulsive action in clinical and experimental observations’5’25. Repeated applications of MAP are known to cause a psychosis very similar to paranoid schizophrenia29, and MAP and amphetamine are considered to have an anticonvulsive action at low doses17,27,28,32. It is well known that disappearance of epileptic discharge or seizures is sometimes accompanied by the development of psychotic symptomatology, referred to as forced normalization35,36. In addition, limbic structures (amygdala, hippocampus) are suspected of being involved in the pathophysiology of psychosis as well as epilepsy 7,10,23. Therefore, we consider it important to clarify the effects of chronic treatment of HPD and MAP on seizures generated in the limbit area. METHODS Animals
Fourteen cats of both sexes (6 females, 8 males), weighing 2-3 kg, were divided into 2 groups of 7 (3 females, 4 males each) for HPD and MAP assessment. Kindling
The cats were anesthetized with pentobarbital (25 mg/kg, i.p.). Tripolar (stimulating lead) or bipolar (recording lead) electrodes (0.2 mm in diameter), implanted bilaterally into the dorsal hippocampus (DHP), ventral hippocampus (VHP) and lateral amygdala (AM), were attached to a head socket with dental cement. One week later the cats were subjected to the low-frequency kindling procedure, and EEG was recorded on a 9-channel Nihon-Koden machine. Each cat was placed in an observation chamber for 10 min, and then received bipolar stimulation in the left VHP bipolary once daily, with 2 mA biphasic squarewave pulses, each pulse of 1 msec duration, using a Nihon-Koden SEN-7103 stimulation and constant current units. The stimulating-pulse interval was
1 1
23 II
,, ,.,p
Fig. 1. Triggering of generalized tonic-clonic seizure by a 300 msec interval stimulation. Left-side ventral hippocampus was stimulated. AM, amygdala; VHP, ventral hippocampus; DHP, dorsal hippocampus; 1, start of stimulation; 2, triggering of AD; 3, end of stimulation; 4, end of AD. In this case pulsenumber threshold (PNT) and the AD duration (ADD) is 8 (the number of stimulating pulses from 1 to 2) and 100.7 set, respectively.
set at 300 msec. Epileptic afterdischarge (AD) was defined as epileptiform spikes 3 times the base line amplitude with a frequency greater than the stimulating pulse interval (300 msec). Low-frequency stimulation was stopped immediately after the appearance of AD. Fig. 1 shows the AD triggered with a 300 msec interval stimulation in one cat. Behavioural development of seizures was divided into five stages, modified from the conventional classification3’ as follows: (1) attention response or immobility; (2) facial twitching; (3) tonic extension of contralateral forepaw; (4) generalized clonic jerking; (5) generalized convulsion with falling down. Generalized tonic-clonic, stage-5 seizures developed within 32-65 (mean 42.6) AD triggering stimulations. The 14 cats, which reliably manifested stage-5 seizures when stimulated with 300 msec intervals, were used for the pharmacological study described below. Drug administration and monitoring
After cats experienced 5 stage-5 seizures, the effects of HPD and MAP on the kindled cats were tested. Cats received 17 once daily treatments with HPD (0.5, 1.0, 2.0 mg/kg/day, p.o.) and MAP (1.0, 2.0, 4.0) at 13:OO on each day. Each drug was administered as small tablets, and a con-
215
trol experiment was done with placebo tablets in order: placebo, HPD 0.5, 1.0,2-O, MAP 1.0,2.0, 4.0 mg. Each cat received electrical stimulations at 2 h after the drug administration (15:OO) on the lst, 5th, 9th, 13th and 17th day of drug treatment and the 4th and 8th day of ~thdrawal period. We recorded the three seizure parameters (PNT, ADD and seizure stage) and the behavioral changes caused by drug administration. Since the same cats were used repeatedly, at least 2 weeks elapsed before a different dose was administered. During this inter-testing period, each cat was stimulated with a 96 h interval to follow the effects of drug withdrawal and to confirm the chronologically constant feature of the three parameters. Blood samples of 4 ml were obtained from a retained catheter inserted into the right jugular vein under the same schedule as that of electrical stimulation. Serum HPD levels were then determined by using reverse phase liquid chromatography with electrochemical detection based on the method of Kopri et a1.14.Standard curves were prepared with serum samples of cats treated with saline. Statistics The drug effects on PNT and ADD were assessed by Wilcoxon matched-pairs signed-rank test. Changes in these parameters over the time during the drug-free period were examined by ANOVA.
TABLE I The serum haloperidof (HPD) levelsat each dose Serum HPD level (@ml)
HPD dose (mgJkg!day)
0.5 1.0 2.0
Day ofmonitoring I 5 9
13
17
24.1 33.5 62.9
29.5 36.6 83.0
21.1 57.8 73.8
27.6 38.9 49.7
RESULTS The serum HPD level at each dosage was determined as shown in Table 1. In general, a dose-dependent increase in serum levels was confirmed, and each value was higher than the optimal range in clinical use. Seizure indicators returned to predrug levels by
34.1 39.9 99.6
27.3 + 10.3 41.3 k4.3 75.8+ 18.4
the 8th day of withdrawal period, and then did not significantly change over the time during the drugfree period (data not shown) as reported previouslY20,21~ MAP treatment with 4 mg/kgfday caused severe and prolonged stereotyped behaviors and poor appetite. For these reasons drug treatment was discontinued after 9 days at this dose. 0 HPD 0.5 A HPD 1.0 0 HPD 2.0(mg/kg/day)
PNT (%I
loo-
TREATMENT 5 ADD
9
13
ti 17
21 25 DAY
0 HPD 0.5 A HPD 1.0 0 HPD 2.0(mg/kg/day)
(%I Following the completion of experiment, localization of the stimulating electrodes was verified in each cat. The animals were perfused with saline and 10% formalin solution. The brains were removed and embedded with paraffin and serially sectioned every 30 pm to confirm the electrode placement.
Mean + SE
1 oo-
4 TREATMENT
I)
501 PRE
1
5
9
13
17
21 25 DAY
Fig. 2. Effects of chronic haloperidol (HPD) treatment (0.5, 1.0,2.0 mg/kg/day, p.o., 17 days) on the pulse number threshold (PNT) and the AD duration (ADD) of hippocampal kindled seizures. Values are expressed as percentage of pred~glevels(O,5mg, 11.4 + 1.7,98.6 + 9.1; l.Omg, 12.3 + 2.2, 92.6 t 17.1; 2.0 mg, 11.9 f 1.7, 104.3 i 13.1, respectively), and represent mean + SE (n = 7) for each day. *P < 0.05; **P < 0.02 as compared to predrug (Wilcoxon matched-pairs signed-rank test).
216 PNT
- MAP 1.0,2.0
(%I
oMAP 1.0 A MAP 2.0 0 MAP 4.0
TREATMENT
501 PRE
1
5
9
13
MAP 1.0,2.0 IREATLENT
ADD (%I
I
MAP 4.0 1i
17
b
21 25 DAY
o MAP 1 .O * MAP 2.0 0 MAP 4.0 (mg/kg/day)
day of drug treatment and on the 4th day of the withdrawal period. MAP, 1.0 mg/kg/day, produced no significant effect on PNT and ADD. MAP, 2.0 mg/kg/day, significantly decreased PNT on the 9th and 17th day of drug treatment, and decreased ADD on the lst, 5th, 9th, 13th and 17th day of drug treatment. MAP, 4.0 mg/kg/day, significantly decreased PNT on the 1st and 5th day of drug treatment, and the 4th day of withdrawal period. No regression of behavioral seizure stage was observed during treatments. As shown in Fig. 4, histological examination showed that all stimulating electrodes were located within the ventral hippocampus . DISCUSSION
50’ PRE
1
5
9
13
17
21 25 DAY
Fig 3. Effects of chronic methamphetamine (MAP) treatment (1.0,2.0mg/kg/day,p.o., 17days;4.0mg/kg/day,p.o.,9days) on the pulse number threshold (PNT) and the AD duration (ADD) in hippocampal kindled seizures. Values are expressed as percentage of predrug levels (1.0 mg, 12.3 + 1.1, 105.1 + 12.6; 2.0 mg, 14.6 + 2.0, 109.7 f 12.4; 4.0 mg, 13.3 + 1.2,98.9 + 9.8, respectively), and represent mean + SE (n = 7) for each day. *P < 0.05, **P < 0.02 as compared to predrug (Wilcoxon matched-pairs signed-rank test).
The results are summarized in Figs. 2 and 3. Placebo treatment did not change PNT and ADD significantly compared to the predrug values (mean ? SE; 12.6 + 0.5, 103.9 f 4.4, ANOVA; F,, 48 = 0.30, 0.68, respectively). Each predrug value did not statistically indicate significant difference from placebo treatment (ANOVA; F,, 42 = 0.38, 0.22, respectively). HPD, 0.5 mg/kg/day, significantly decreased PNT on the 5th day of drug treatment, and decreased ADD on the 5th and 9th day of drug treatment. HPD, 1.0 mg/kg/day, significantly decreased ADD on the 5th 9th, 13th and 17th day of drug treatment without affecting PNT. HPD, 2.0 mg/kg/day, significantly decreased PNT on the 5th, 9th, 13th and 17th day of drug treatment, and decreased ADD on the lst, 5th, 9th, 13th and 17th
It is of interest to compare the results of this study with that of previous studies’8’19 which described the chronic effect of HPD and MAP on amygdala (AM) kindled seizures. Since the same cats were used and order of application of dosages was not randomized, it is possible that dose-response relation could have been affected by sensitization or tolerance to the drug effects. Concern-
Fig. 4. Localization of stimulating electrode sites in the ventral hippocampus.
217
ing drug administrations, however, this study on HP seizures was done under the same procedure as previous on AM seizures, so we consider that these studies are comparable. First, HPD, 0.5 mg/kg/day, transiently decreased PNT and ADD of HP seizures at the initial stage of treatment, whereas the same dosage produced no significant effect on AM seizures. Second, HPD, 1.0 mg/kg/day, decreased only ADD without affecting PNT of HP seizures. The same dosage decreased PNT and ADD of AM seizures during the treatment. Following the drug, there was a one-week increase in PNT of AM seizure during the withdrawal. Third, HPD, 2.0 mg/kg/day, decreased PNT of HP seizures. The same dosage decreased PNT of AM seizures followed by a return to control level during the treatment. Following the drug, there was a 2-week increase in PNT of AM seizures during withdrawal. ADD of AM and HP seizure decreased during the treatment at this dosage. These results indicate that HPD has a significant proconvulsive action on seizures generated from limbic structures. We consider that the decrease in seizure duration without regression of seizure stage during HPD treatment did not simply indicate an anticonvulsive action of HPD, since there is a possibility that acceleration of secondary generalization can reduce the entire duration of induced seizures. It appears from these data that chronic treatment with HPD revealed two major pharmacological differences between AM and HP seizures. HPD decreased the seizure threshold of AM-stimulated seizures more easily than that of HP-stimulated seizures. Moreover, only in AM seizures was there a development of tolerance toward the decrease of seizure threshold during HPD treatment and a rebound-like lengthy increase of seizure threshold during the withdrawal, suggesting a late-onset development of antiepileptic effects. Fourth, MAP 1.0 mg!kg/day treatment produced no significant effect on AM and HP seizures. Fifth, MAP 2.0 mg/kg/day decreased PNT and ADD of HP seizure during the treatment. The same dosage increased PNT of AM seizure on the initial treatment day, followed by a PNT decrease
at the late stage of treatment. Following the drug, there was a rebound-like PNT increase during the withdrawal. This dosage produced no significant effect on ADD of AM seizures. Sixth, MAP 4.0 mg/kg/day decreased PNT during the treatment without affecting ADD of HP seizures. This dose has not been tested on AM seizures. These results suggest that the MAP sensitization may induce an elevation of seizure susceptibility in the limbic area 13.There are 2 maj or p harmacological differences between the response of AM and HP seizures to chronic MAP treatment. Although chronic MAP treatment decreased the seizure threshold in AM and HP seizures, a threshold increase at the initial stage of treatment and withdrawal was observed in AM seizure but not in HP seizure. Moreover, the seizure duration decreased in HP seizure but not in AM seizure. To our knowledge there are no previous studies that have convincingly demonstrated regional difference of psychotropic drugs on seizures of limbic origin. We recently reported that the actions of anticonvulsants (e.g., phenytoin, carbamazepine, valproic acid) on HP seizure are entirely different from their actions on AM seizure4. However another possible mechanism, which does not depend on the pharmacological characteristics of each drug itself, should be taken into account. The regional difference may be caused by the regional difference of brain HPD and MAP levels’2,24since a biphasic effect of amphetamine on experimental seizures has been reported” which showed that a low dose decreased it. If this is the case, lower doses of MAP than tested in this study should in crease the seizure threshold of HP. Moreover, although it is known that the occurrence of AM kindling causes alternations of dopamine function5*8,9,we do not know of any other studies concerning the effects of HP kindling on dopamine function. However HP kindling may have caused other characteristics distinguishable from that of AM kindling. In particular HP kindling may suppress the hypersensitivity of dopamine receptors which is suspected of retarding the AM kindling during HPD withdrawal period”. Alternatively, or perhaps additionally, it should be considered that the contribution of other brain areas (e.g.,
218
substantia nigra’6T22)might be different between AM and HP kindled seizures. A number of investigators have used kindling in animals in an attempt to substantiate our understanding of the complex and controversial relationship between psychosis and epilepsy. This paradoxical relationship is embodied in the ‘affinity’ and ‘antagonism’ hypotheses of epilepsy and psychosis’. The antagonism hypothesis fits well with the studies of Sato et a1.31*32,33,34 on AM kindling26. There might be some relationship between the results we obtained from HP kindled seizures and the affinity hypothesis. If seizure susceptibility reflects neural excitability, our findings may show that a dopamine agonist (MAP) inhibits AM and excites HP. It is possible that these interesting findings might contribute to REFERENCES 1 Adamec, R.E., Does kindling model anything clinically relevant? Biol. Psychiatry, 27 (1990) 249-279. 2 Antelman, SM., Kocan, D., Edwards, D.J., Knopf, S., Peral, J.M. and Stiller, R., Behavioral effects of a single neuroleptic treatment grow with the passage of time, Brain Res., 385 (1986) 58-67. 3 Emori, K., Minabe, Y. and Kurachi, M., A biphasic change of afterdischarge threshold during the kindling process, Brain Res., 509(1990) 355-357. 4 Emori, K. and Minabe, Y., Effects of anticonvulsants on hippocampus-generating seizures, Brain Res., 511 (1990) 217-221. 5 Engel Jr., J. and Sharpless, N.S., Long-lasting depletion in the rat amygdala induced kindling stimulation, Brain Res., 136 (1977) 381-386. 6 Engel Jr., J., Ackerman, R.F., Caldecott-Hazard, S. and Kuhl, D.E., Epileptic activation of antagonistic systems may explain paradoxical features of experimental and human epilepsy: a review and hypothesis. In: J.A. Wada (Ed.), Kindling 2, Raven Press, New York, 1981, pp. 193-217. 7 Falkai, P. and Bogerts, B., Cell loss in the hippocampus of schizophrenics, Eur. Arch. Psychiatr. Neural. Sci., 236 (1986) 154-161. 8 Farjo, I.B. and Blackwood, D.H.R., Reduction in tyrosine hydroxylase activity in the rat amygdala induced by kindling stimulation, Brain Res., 153 (1978) 423-426. 9 Gee, K.W., Warn, E.K. and Hollinger, M.A., Effect of amygdaloid kindling on dopamine-sensitive adenylate cyclase activity in rat brain, Exp. Neurol., 70 (1980) 192-199. 10 Gee, K.W., Killam, E.K. and Hollinger, M.A., Effects of haloperidol-induced dopamine receptor supersensitivity on kindled seizure development, J. Pharmacol. Exp. Ther., 225 (1983) 70-76.
the elucidation of the pathophysiology of dopamine-induced psychosis or schizophrenia. As Engel suggest8, some inhibitory systems (DA) could be potentiated which are antagonistic to seizure expression, at the same time other systems that are proconvulsive are maturing26. We also consider that these interactions could determine the levels of seizure susceptibility.
ACKNOWLEDGEMENTS We thank Mr. Minoru Hasegawa and Mr. Masahiko Murata for their technical assistance. This study was partially supported by the Japanese Ministry of Education, Science and Culture Grant-in Aid for Scientific Research, 63770809. 11 Gloor, P., Olivier, A., Quesney, L.F. and Andermann, F., The role of the limbic system in experimental phenomena of temporal lobe epilepsy, Ann. Neural., 12 (1982) 129-144. 12 Glowinski, J., Axelrod, J. and Iversen, L.L., Regional study of catecholamines in the rat brain. IV. Effects of drugs on the disposition and metabolism of 3H-norepinephrine and 3H-dopamine, J. Pharmacol. Exp. Ther., 153 (1966) 30-41. 13 Kirkby, R.D. and Kokkinidis, L., Evidence for a relationship between amphetamine sensitization and electrical kindling of the amygdala, Exp. Neurol., 97 (1987) 270-279. 14 Kopri, E.R., Phelps, B.H., Granger, H., Chang, W.-H., Linnoil, M., Meek, J.L. and Wyatt, R.J., Simultaneous determination of haloperidol and its reduced metabolite in serum and plasma by isocratic liquid chromatography with electrochemical detection, C&z. Chem., 29 (1983) 624-628. 15 Lipka, L.J. and Lathers, C.M., Psychoactive agents, seizure production, and sudden death in epilepsy, J. C&z. Pharmacol., 27 (1987) 169- 183. 16 Lothman, E.W., Hatlelid, J.M. and Zorumski, C.F., Functional mapping of limbic seizures originating in the hippocampus: a combined 2-deoxyglucose and electrophysiologic study, Brain Res., 360 (1985) 92-100. 17 Minabe, Y., Tanii, Y. and Kurach, M., Acute effect of some psychotropic drugs on low-frequency amygdaloid kindled seizures, Biol. Psychiatry, 22 (1987) 1444-1450. 18 Minabe, Y., Tsutsumi, M. and Kurachi, M., Effects of chronic haloperidol treatment on amygdaloid seizure generation in cats, Psychopharmacology, 94 (1988) 259-262. 19 Minabe, Y., Emori, K. and Kurachi, M., Effects of chronic
treatment of methamphetamine and imipramine on amygdaloid seizure’s generation, Jpn. J. Psychiatr. Neural., 42 (1988) 337-343.
219 20 Minabe, Y., Emori, K. and Kurachi, K., Effects of chronic lithium treatment on limbic seizure generation in cat, Psychopharmacology, 96 (1988) 391-394. 21 Minabe, Y., Emori, K. and Kurachi, M., An evidence of ‘post-seizure excitation’ in feline-kindled seizures, Bruin Res., 486 (1989) 201-203. 22 Morimoto, K. and Goddard, G.V., The substantia nigra is an important site for the containment of seizure generalization in the kindling model of epilepsy, Epilepsia, 28 (1987) l-10. 23 Nielsen, H. and Kristensen, O., Personality correlates of sphenoidal EEG-foci in temporal lobe epilepsy, Acta Neurol. Scund., 64 (1981) 289-300. 24 Oka, M., Asano, K., Sekine, Y. and Kadokawa, T., Effect of repeated treatment of haloperidol on self-stimulation behavior in relation to regional drug levels in brain, Jpn. J. Pharmacol., 31(1981) 246P. 25 Oliver, A.P., Luchins, D.J. and Wyatt, R.J., Neuroleptic induced seizures, Arch. Gen. Psychiatry, 39 (1982) 206-209. 26 Pollock, DC., Models for understanding the antagonism between seizures and psychosis, Prog. Neuro-Psychopharmacol. Biol. Psychiatry, ll(l987) 483-504. 27 Riffee, W.H. and Gerald, MC., Effects of amphetamine isomers and CNS catecholaminergic blockers on seizures in mice, Neuropharmacology, 15 (1976) 677-682. 28 Riffee, W.H. and Gerald, M.C., The effects of chronic administration and withdrawal of (+)-amphetamine on seizure threshold and endogenous catecholamine concentra-
tions and their rates of biosynthesis in mice, Psychopharmacology, 51(1977) 175-179.
29 Robinson, T.E. and Becker, J.B., Enduring changes in brain and behavior produced by chronic amphetamine administration: a review and evaluation of animal models of amphetamine psychosis, Brain Res. Rev., 11 (1986) 157-198. 30 Sato, M., A study on psychomotor epilepsy with kindled cat preparations, Folia Psychiatr. Neural. Jpn., 30 (1976) 425-434.
31 Sato, M., Hikasa, N. and Otsuki, S., Experimental epilepsy, psychosis and dopamine receptor sensitivity, Biol. Psychiatry, 13 (1977) 537-540. 32 Sato, M., Tomoda, T., Hikasi, N. and Otsuki, S., Inhibition
of amygdaloid kindling by chronic pretreatment with cocaine or methamphetamine, Epilepsia, 21(1980) 497-507. 33 Sato, M., Chen, C., Akiyama, K. and Otsuki, S., Acute exacerbation of paranoid psychotic state after long-term abstinence in patients with previous methamphetamine psychosis, Biol. Psychiurry, 18 (1983) 429-440. 34 Sato, M., Long-lasting hypersensitivity to methamphetamine following amygdaloid kindling in cats: the relationship between limbic epilepsy and the psychotic state, Biol. Psychiutty, 18 (1983) 525-536. 35 Wolf, P. and Trimble, M.R.,
Biological antagonism and epileptic psychosis, Br. J. Psychiatry, 146 (1985) 272-276. 36 Wolf, P., Forced normalization. In: M.R. Trimble and T.G. Bolwig (Eds.), Aspects of Epilepsy and Psychiatry, Wiley, Chichester, 1985, pp. 101-115.
Epilepsy Res., 8 (1991) 213-219
Elsevier EPIRES 00391
Effects of chronic treatment with haloperidol and methamphetamine on hippocampal kindled seizures in the cat
Kenji Emori, Yoshio Minabe*, Yasuyuki Tanii and Masayoshi Kurachi Department of Neuropsychiatry,
Faculty of Medicine, Toyama Medical and Pharmaceutical University, Sugitani, Toyama (Japan)
(Received 28 June 1990; accepted 18 November 1990) Key words: Kindling; Amygdala; Hippocampus;
Haloperidol; Methamphetamine;
Cat
We assessed the effects of chronic treatment with haloperidol (O.S-2 mg/kg/day, p.o., 17 days) and methamphetamine (l-2 mg/kg/ day, p.o., 17 days; 4 mg/kg/day, p.o. 9 days) on hippocampal kindled seizures using a kindling procedure with low-frequency (about 3 Hz) electrical stimulation in cats. The number of stimulating pulses required to trigger epileptic afterdischarge (pulse-number threshold, PNT) was considered an indicator of seizure threshold. Haloperidol, 0.5 and 1.0 mg/kg, reduced the duration of epileptic afterdischarge (afterdischarge duration, ADD) without affecting PNT, and 2.0 mg/kg strongly reduced PNT and ADD. Methamphetamine, 2.0 mg/kg, reduced PNT and ADD, and 4.0 mg/kg preferentially reduced PNT. The effects of the two drugs on hippocampal kindled seizures were found to be partially opposite to those on amygdala kindled seizures, suggesting the different response of these limbic structures to dopamine receptor manipulation.
INTRODUCTION We have recently reported pharmacological studies using a kindling model of epilepsy induced with low-frequency electrical stimulations (2-3 Hz), referred to as the low-frequency kindling technique’8~‘9~20.In these studies, chronic effects of psychotropic drugs on seizures kindled from the * Present address: Department of Psychiatry and Behavioral Science, State University of New York at Stony Brook, Stony Brook, NY 11794-8790, U.S.A. Abbreviations: ADD, afterdischarge duration; AM, amygdala; MAP, methamphetamine; HPD, haloperidol; HP, hippocampus; PNT, pulse-number threshold. Correspondence to: Kenji Emori, Dept. of Neuropsychiatry, Faculty of Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-01, Japan.
0920-1211/91/$03.50 0 1991 Elsevier Science Publishers B.V.
2 limbic structures, amygdala and hippocampus, were evaluated. The low-frequency kindling technique has a great advantage3 in quantitatively and chronologically assessing the seizure threshold and the severity of induced seizure. The former was indicated by the number of stimulating pulses required to trigger seizures (pulse-number threshold, PNT), and the latter was indicated by the duration of epileptic afterdischarge on EEG record (afterdischarge duration, ADD) and the behavioral manifestations of induced seizures. Since a previous study showed that the effect of chronic lithium treatment on limbic seizures is dependent on the location of seizure origin*‘, we decided to study the chronic effect of haloperidol (HPD) and methamphetamine (MAP) on seizures generated from stimulation of the hippocampus (HP), and compare the data thus obtained with the results of
214
previous studies of amygdala (AM) kindled seizures18’19,which were done under the same conditions as this study. HPD is usually administered repetitively in clinical use and its antipsychotic efficacy requires at least l-2 weeks of continuous medication2. HPD is known to have a proconvulsive action in clinical and experimental observations’5’25. Repeated applications of MAP are known to cause a psychosis very similar to paranoid schizophrenia29, and MAP and amphetamine are considered to have an anticonvulsive action at low doses17,27,28,32. It is well known that disappearance of epileptic discharge or seizures is sometimes accompanied by the development of psychotic symptomatology, referred to as forced normalization35,36. In addition, limbic structures (amygdala, hippocampus) are suspected of being involved in the pathophysiology of psychosis as well as epilepsy 7,10,23. Therefore, we consider it important to clarify the effects of chronic treatment of HPD and MAP on seizures generated in the limbit area. METHODS Animals
Fourteen cats of both sexes (6 females, 8 males), weighing 2-3 kg, were divided into 2 groups of 7 (3 females, 4 males each) for HPD and MAP assessment. Kindling
The cats were anesthetized with pentobarbital (25 mg/kg, i.p.). Tripolar (stimulating lead) or bipolar (recording lead) electrodes (0.2 mm in diameter), implanted bilaterally into the dorsal hippocampus (DHP), ventral hippocampus (VHP) and lateral amygdala (AM), were attached to a head socket with dental cement. One week later the cats were subjected to the low-frequency kindling procedure, and EEG was recorded on a 9-channel Nihon-Koden machine. Each cat was placed in an observation chamber for 10 min, and then received bipolar stimulation in the left VHP bipolary once daily, with 2 mA biphasic squarewave pulses, each pulse of 1 msec duration, using a Nihon-Koden SEN-7103 stimulation and constant current units. The stimulating-pulse interval was
1 1
23 II
,, ,.,p
Fig. 1. Triggering of generalized tonic-clonic seizure by a 300 msec interval stimulation. Left-side ventral hippocampus was stimulated. AM, amygdala; VHP, ventral hippocampus; DHP, dorsal hippocampus; 1, start of stimulation; 2, triggering of AD; 3, end of stimulation; 4, end of AD. In this case pulsenumber threshold (PNT) and the AD duration (ADD) is 8 (the number of stimulating pulses from 1 to 2) and 100.7 set, respectively.
set at 300 msec. Epileptic afterdischarge (AD) was defined as epileptiform spikes 3 times the base line amplitude with a frequency greater than the stimulating pulse interval (300 msec). Low-frequency stimulation was stopped immediately after the appearance of AD. Fig. 1 shows the AD triggered with a 300 msec interval stimulation in one cat. Behavioural development of seizures was divided into five stages, modified from the conventional classification3’ as follows: (1) attention response or immobility; (2) facial twitching; (3) tonic extension of contralateral forepaw; (4) generalized clonic jerking; (5) generalized convulsion with falling down. Generalized tonic-clonic, stage-5 seizures developed within 32-65 (mean 42.6) AD triggering stimulations. The 14 cats, which reliably manifested stage-5 seizures when stimulated with 300 msec intervals, were used for the pharmacological study described below. Drug administration and monitoring
After cats experienced 5 stage-5 seizures, the effects of HPD and MAP on the kindled cats were tested. Cats received 17 once daily treatments with HPD (0.5, 1.0, 2.0 mg/kg/day, p.o.) and MAP (1.0, 2.0, 4.0) at 13:OO on each day. Each drug was administered as small tablets, and a con-
215
trol experiment was done with placebo tablets in order: placebo, HPD 0.5, 1.0,2-O, MAP 1.0,2.0, 4.0 mg. Each cat received electrical stimulations at 2 h after the drug administration (15:OO) on the lst, 5th, 9th, 13th and 17th day of drug treatment and the 4th and 8th day of ~thdrawal period. We recorded the three seizure parameters (PNT, ADD and seizure stage) and the behavioral changes caused by drug administration. Since the same cats were used repeatedly, at least 2 weeks elapsed before a different dose was administered. During this inter-testing period, each cat was stimulated with a 96 h interval to follow the effects of drug withdrawal and to confirm the chronologically constant feature of the three parameters. Blood samples of 4 ml were obtained from a retained catheter inserted into the right jugular vein under the same schedule as that of electrical stimulation. Serum HPD levels were then determined by using reverse phase liquid chromatography with electrochemical detection based on the method of Kopri et a1.14.Standard curves were prepared with serum samples of cats treated with saline. Statistics The drug effects on PNT and ADD were assessed by Wilcoxon matched-pairs signed-rank test. Changes in these parameters over the time during the drug-free period were examined by ANOVA.
TABLE I The serum haloperidof (HPD) levelsat each dose Serum HPD level (@ml)
HPD dose (mgJkg!day)
0.5 1.0 2.0
Day ofmonitoring I 5 9
13
17
24.1 33.5 62.9
29.5 36.6 83.0
21.1 57.8 73.8
27.6 38.9 49.7
RESULTS The serum HPD level at each dosage was determined as shown in Table 1. In general, a dose-dependent increase in serum levels was confirmed, and each value was higher than the optimal range in clinical use. Seizure indicators returned to predrug levels by
34.1 39.9 99.6
27.3 + 10.3 41.3 k4.3 75.8+ 18.4
the 8th day of withdrawal period, and then did not significantly change over the time during the drugfree period (data not shown) as reported previouslY20,21~ MAP treatment with 4 mg/kgfday caused severe and prolonged stereotyped behaviors and poor appetite. For these reasons drug treatment was discontinued after 9 days at this dose. 0 HPD 0.5 A HPD 1.0 0 HPD 2.0(mg/kg/day)
PNT (%I
loo-
TREATMENT 5 ADD
9
13
ti 17
21 25 DAY
0 HPD 0.5 A HPD 1.0 0 HPD 2.0(mg/kg/day)
(%I Following the completion of experiment, localization of the stimulating electrodes was verified in each cat. The animals were perfused with saline and 10% formalin solution. The brains were removed and embedded with paraffin and serially sectioned every 30 pm to confirm the electrode placement.
Mean + SE
1 oo-
4 TREATMENT
I)
501 PRE
1
5
9
13
17
21 25 DAY
Fig. 2. Effects of chronic haloperidol (HPD) treatment (0.5, 1.0,2.0 mg/kg/day, p.o., 17 days) on the pulse number threshold (PNT) and the AD duration (ADD) of hippocampal kindled seizures. Values are expressed as percentage of pred~glevels(O,5mg, 11.4 + 1.7,98.6 + 9.1; l.Omg, 12.3 + 2.2, 92.6 t 17.1; 2.0 mg, 11.9 f 1.7, 104.3 i 13.1, respectively), and represent mean + SE (n = 7) for each day. *P < 0.05; **P < 0.02 as compared to predrug (Wilcoxon matched-pairs signed-rank test).
216 PNT
- MAP 1.0,2.0
(%I
oMAP 1.0 A MAP 2.0 0 MAP 4.0
TREATMENT
501 PRE
1
5
9
13
MAP 1.0,2.0 IREATLENT
ADD (%I
I
MAP 4.0 1i
17
b
21 25 DAY
o MAP 1 .O * MAP 2.0 0 MAP 4.0 (mg/kg/day)
day of drug treatment and on the 4th day of the withdrawal period. MAP, 1.0 mg/kg/day, produced no significant effect on PNT and ADD. MAP, 2.0 mg/kg/day, significantly decreased PNT on the 9th and 17th day of drug treatment, and decreased ADD on the lst, 5th, 9th, 13th and 17th day of drug treatment. MAP, 4.0 mg/kg/day, significantly decreased PNT on the 1st and 5th day of drug treatment, and the 4th day of withdrawal period. No regression of behavioral seizure stage was observed during treatments. As shown in Fig. 4, histological examination showed that all stimulating electrodes were located within the ventral hippocampus . DISCUSSION
50’ PRE
1
5
9
13
17
21 25 DAY
Fig 3. Effects of chronic methamphetamine (MAP) treatment (1.0,2.0mg/kg/day,p.o., 17days;4.0mg/kg/day,p.o.,9days) on the pulse number threshold (PNT) and the AD duration (ADD) in hippocampal kindled seizures. Values are expressed as percentage of predrug levels (1.0 mg, 12.3 + 1.1, 105.1 + 12.6; 2.0 mg, 14.6 + 2.0, 109.7 f 12.4; 4.0 mg, 13.3 + 1.2,98.9 + 9.8, respectively), and represent mean + SE (n = 7) for each day. *P < 0.05, **P < 0.02 as compared to predrug (Wilcoxon matched-pairs signed-rank test).
The results are summarized in Figs. 2 and 3. Placebo treatment did not change PNT and ADD significantly compared to the predrug values (mean ? SE; 12.6 + 0.5, 103.9 f 4.4, ANOVA; F,, 48 = 0.30, 0.68, respectively). Each predrug value did not statistically indicate significant difference from placebo treatment (ANOVA; F,, 42 = 0.38, 0.22, respectively). HPD, 0.5 mg/kg/day, significantly decreased PNT on the 5th day of drug treatment, and decreased ADD on the 5th and 9th day of drug treatment. HPD, 1.0 mg/kg/day, significantly decreased ADD on the 5th 9th, 13th and 17th day of drug treatment without affecting PNT. HPD, 2.0 mg/kg/day, significantly decreased PNT on the 5th, 9th, 13th and 17th day of drug treatment, and decreased ADD on the lst, 5th, 9th, 13th and 17th
It is of interest to compare the results of this study with that of previous studies’8’19 which described the chronic effect of HPD and MAP on amygdala (AM) kindled seizures. Since the same cats were used and order of application of dosages was not randomized, it is possible that dose-response relation could have been affected by sensitization or tolerance to the drug effects. Concern-
Fig. 4. Localization of stimulating electrode sites in the ventral hippocampus.
217
ing drug administrations, however, this study on HP seizures was done under the same procedure as previous on AM seizures, so we consider that these studies are comparable. First, HPD, 0.5 mg/kg/day, transiently decreased PNT and ADD of HP seizures at the initial stage of treatment, whereas the same dosage produced no significant effect on AM seizures. Second, HPD, 1.0 mg/kg/day, decreased only ADD without affecting PNT of HP seizures. The same dosage decreased PNT and ADD of AM seizures during the treatment. Following the drug, there was a one-week increase in PNT of AM seizure during the withdrawal. Third, HPD, 2.0 mg/kg/day, decreased PNT of HP seizures. The same dosage decreased PNT of AM seizures followed by a return to control level during the treatment. Following the drug, there was a 2-week increase in PNT of AM seizures during withdrawal. ADD of AM and HP seizure decreased during the treatment at this dosage. These results indicate that HPD has a significant proconvulsive action on seizures generated from limbic structures. We consider that the decrease in seizure duration without regression of seizure stage during HPD treatment did not simply indicate an anticonvulsive action of HPD, since there is a possibility that acceleration of secondary generalization can reduce the entire duration of induced seizures. It appears from these data that chronic treatment with HPD revealed two major pharmacological differences between AM and HP seizures. HPD decreased the seizure threshold of AM-stimulated seizures more easily than that of HP-stimulated seizures. Moreover, only in AM seizures was there a development of tolerance toward the decrease of seizure threshold during HPD treatment and a rebound-like lengthy increase of seizure threshold during the withdrawal, suggesting a late-onset development of antiepileptic effects. Fourth, MAP 1.0 mg!kg/day treatment produced no significant effect on AM and HP seizures. Fifth, MAP 2.0 mg/kg/day decreased PNT and ADD of HP seizure during the treatment. The same dosage increased PNT of AM seizure on the initial treatment day, followed by a PNT decrease
at the late stage of treatment. Following the drug, there was a rebound-like PNT increase during the withdrawal. This dosage produced no significant effect on ADD of AM seizures. Sixth, MAP 4.0 mg/kg/day decreased PNT during the treatment without affecting ADD of HP seizures. This dose has not been tested on AM seizures. These results suggest that the MAP sensitization may induce an elevation of seizure susceptibility in the limbic area 13.There are 2 maj or p harmacological differences between the response of AM and HP seizures to chronic MAP treatment. Although chronic MAP treatment decreased the seizure threshold in AM and HP seizures, a threshold increase at the initial stage of treatment and withdrawal was observed in AM seizure but not in HP seizure. Moreover, the seizure duration decreased in HP seizure but not in AM seizure. To our knowledge there are no previous studies that have convincingly demonstrated regional difference of psychotropic drugs on seizures of limbic origin. We recently reported that the actions of anticonvulsants (e.g., phenytoin, carbamazepine, valproic acid) on HP seizure are entirely different from their actions on AM seizure4. However another possible mechanism, which does not depend on the pharmacological characteristics of each drug itself, should be taken into account. The regional difference may be caused by the regional difference of brain HPD and MAP levels’2,24since a biphasic effect of amphetamine on experimental seizures has been reported” which showed that a low dose decreased it. If this is the case, lower doses of MAP than tested in this study should in crease the seizure threshold of HP. Moreover, although it is known that the occurrence of AM kindling causes alternations of dopamine function5*8,9,we do not know of any other studies concerning the effects of HP kindling on dopamine function. However HP kindling may have caused other characteristics distinguishable from that of AM kindling. In particular HP kindling may suppress the hypersensitivity of dopamine receptors which is suspected of retarding the AM kindling during HPD withdrawal period”. Alternatively, or perhaps additionally, it should be considered that the contribution of other brain areas (e.g.,
218
substantia nigra’6T22)might be different between AM and HP kindled seizures. A number of investigators have used kindling in animals in an attempt to substantiate our understanding of the complex and controversial relationship between psychosis and epilepsy. This paradoxical relationship is embodied in the ‘affinity’ and ‘antagonism’ hypotheses of epilepsy and psychosis’. The antagonism hypothesis fits well with the studies of Sato et a1.31*32,33,34 on AM kindling26. There might be some relationship between the results we obtained from HP kindled seizures and the affinity hypothesis. If seizure susceptibility reflects neural excitability, our findings may show that a dopamine agonist (MAP) inhibits AM and excites HP. It is possible that these interesting findings might contribute to REFERENCES 1 Adamec, R.E., Does kindling model anything clinically relevant? Biol. Psychiatry, 27 (1990) 249-279. 2 Antelman, SM., Kocan, D., Edwards, D.J., Knopf, S., Peral, J.M. and Stiller, R., Behavioral effects of a single neuroleptic treatment grow with the passage of time, Brain Res., 385 (1986) 58-67. 3 Emori, K., Minabe, Y. and Kurachi, M., A biphasic change of afterdischarge threshold during the kindling process, Brain Res., 509(1990) 355-357. 4 Emori, K. and Minabe, Y., Effects of anticonvulsants on hippocampus-generating seizures, Brain Res., 511 (1990) 217-221. 5 Engel Jr., J. and Sharpless, N.S., Long-lasting depletion in the rat amygdala induced kindling stimulation, Brain Res., 136 (1977) 381-386. 6 Engel Jr., J., Ackerman, R.F., Caldecott-Hazard, S. and Kuhl, D.E., Epileptic activation of antagonistic systems may explain paradoxical features of experimental and human epilepsy: a review and hypothesis. In: J.A. Wada (Ed.), Kindling 2, Raven Press, New York, 1981, pp. 193-217. 7 Falkai, P. and Bogerts, B., Cell loss in the hippocampus of schizophrenics, Eur. Arch. Psychiatr. Neural. Sci., 236 (1986) 154-161. 8 Farjo, I.B. and Blackwood, D.H.R., Reduction in tyrosine hydroxylase activity in the rat amygdala induced by kindling stimulation, Brain Res., 153 (1978) 423-426. 9 Gee, K.W., Warn, E.K. and Hollinger, M.A., Effect of amygdaloid kindling on dopamine-sensitive adenylate cyclase activity in rat brain, Exp. Neurol., 70 (1980) 192-199. 10 Gee, K.W., Killam, E.K. and Hollinger, M.A., Effects of haloperidol-induced dopamine receptor supersensitivity on kindled seizure development, J. Pharmacol. Exp. Ther., 225 (1983) 70-76.
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