Brain Research, 178 (1979) 545-554 © Elsevier/North-HollandBiomedicalPress
545
DRUG-INDUCED STEREOTYPES AND ASYMMETRIC BEHAVIOUR AFTER SUBSTANTIA NIGRA PARS POSTERIOR (SNPP) LESIONS IN CATS
S. WOLFARTH,E.-F. COELLE,N. N. OSBORNE, K.-H. SONTAG and P. WAND Max-Planck Institute for Experimental Medicine, Department o f Biochemical Pharmacology, HermannRein-Str. 3, D-3400 Goettingen ( G.F.R. ), ( S. IV.) Institute of Pharmacology, Polish Academy of Sciences, 31-343 Krakdw (Poland) and ( N.N.O.) Nuffield Laboratory of Ophthalmology, The University of Oxford, Walton Street, Oxford OX2 6A W (U.K.)
(Accepted March 29th, 1979
SUMMARY Apomorphine- (Apo) and amphetamine- (Amph) induced behavioural phenomena were studied in cats which received either 6-hydroxydopamine (6-OHDA) or electrothermic lesions of the posterior part of the substantia nigra (SNPP). In this species, as in rats, both drugs evoked stereotypies (sniffing and head nodding) and an enhancement of locomotor activity. However, distinct differences between the reactions of cats and rats to both drugs were found, the most evident effect being the lack of sterotyped gnawing and licking. By correlating the data on behaviour, the histological examination showing the size and location of the lesions, and the dopamine (DA) content of the corresponding caudate nuclei, it is concluded that the fewer DA-specific neurons lesioned in the SNPP, the more pronounced was the ipsilateral asymmetric behaviour. We suggest, therefore, that the ipsilateral asymmetric behaviour in cats following Apo- and Amph-treatment is due to the destruction of a non-catecholaminergic output. INTRODUCTION Apomorphine (Apo) and amphetamine (Amph) produce a characteristic behavioural syndrome in rats, known as stereotyped behaviour z,17. In rats with a unilateral lesion of the dopamine (DA) cells of the substantia nigra (SN), the two compounds additionally produce a rotational (asymmetric) behaviour3,~l,zL From these studies, it has been suggested that 6-hydroxydopamine (6-OHDA) lesions of the nigrostriatal pathway result in the dopamine receptors in the neostriatum becoming supersensitive and that Apo injection thereafter causes a rotation away from the lesioned side~L These models of stereotyped and rotational behaviour have been extensively investigated in rats. In contrast to the well-known effects of Apo and Amph
546 in the rat, there is scanty information on the behavioural effects of these drugs in the cat, and no data, to our knowledge, has been published on the action of these agents in cats with lesions of the SN. This lack of information is rather unsatisfactory, as the cat is the animal most commonly used for neurophysiological studies, contributing largely to our understanding of higher nervous system function. Therefore, experiments were designed to compare the effects of both Apo and Amph on cats before and after receiving various types of lesions of the posterior part of SN (SNPP). We chose SNPP, since it has been suggested that this part of SN is involved in mediation of Parkinsonian rigidity via a descending nigro-reticulo-spinal pathway 12. METHODS Experiments were carried out on cats of either sex (approximately 2.5 kg body weight). The lesions were stereotaxically induced 20 under pentobarbital (Nembutal, Abbot) anaesthesia (35 mg/kg i.p.). Cats were divided into 5 groups: Group 1 were sham-operated with stainlesssteel cannulae implanted in both SN (control group); Group 2 received an injection of 1% ascorbic acid only into the right SNPP; Group 3, the right SNPP received 6OHDA (10/~g) dissolved in 1% ascorbic acid while the left SNPP received solvent alone; Group 5, the right SNPP received 6-OHDA (10 #g) dissolved in chilled water and bubbled with N2. The left SNPP received chilled water only. The total volume was 4 #1, which was divided into two 2 #1 portions each being stereotaxically injected into SNPP using two different sets of co-ordinates (A 4.0, L 5.0, H--3.0 and A 2.0, L 4.0, H --3.0); and Group 4, the right SNPP was electrothermically lesioned employing two sets of stereotaxic target co-ordinates (A 4.0, L 3.0, H --5.0 and A 2.0, L 2.0, H --5.5; 45 ° lateral inclination). The tip of the lesion electrode was heated 4 times up to 70 °C for 15 sec (David Kopf Radiofrequency Lesion Maker), twice at the above mentioned stereotaxic target points and twice after the electrode tip was moved 2 mm back. Additionally, the right SNPP of 3 cats received 6-OHDA (10/~g), dissolved in 0.1 ,~Jo ascorbic acid while the left SNPP was injected with 0.1% ascorbic acid only. The speed of the injections was about 0.5/A/min. Cats from the Groups 2-5 were submitted to behavioural tests 12-58 days, 18-21 days, 38-50 days and 66-71 days, respectively, after the lesion in the course of which Amph (D-amphetamine sulfate, E. Merck, Darmstadt; 5 mg/kg i.p.) and Apo (apomorphine hydrochloride, I.C.N. Pharmaceuticals, Eschwege; 2 mg/kg s.c.) were injected. The behavioural effects produced by these drugs were filmed in a 2 × 3 m room (22 °C room temperature). Cats were individually tested and received both compounds at one week intervals. The behavioural phenomena, with the exception of asymmetric behaviour, were scored from 0 to 3 according to their intensity. Mean responses were calculated from 6 different observation periods of individuals cats. Ten minute periods were used for Apo and 20 min periods for Amph, the whole examination period being 60 min for Apo and 120 min for Amph. The scoring of the asymmetric behaviour was as follows.
547
°1
P
Fig. 1. Cannula tracks in formalin-fixed and haematoxylin-stained cross-sections of cat brain in the positions A 4.0 (A) and A 2.0 (B) a0 26 days after injection of 10 #g 6-OHDA in 1% ascorbic acid into the right substantia nigra (arrows) divided into two portions of 2/~1. On the left, only the corresponding solvent volumes were injected. One injection track (A) affected structures of the cerebral peduncle. The diffusion of 6-OHDA should be considered to be of a diameter of 1.5-2.0 mm from the end of the cannula tip.
548 One point was given to an animal which occasionally held its head and neck to one side and turned its body in the same direction; 2 points were given when the head and neck were consistently held to one side (this was associated with a body twist to the same side and occasional spontaneous circling behaviour in the same direction); 3 points, when periods of spontaneous circling activity (head-to-tail) were present but did not exceed 2 turns/min; and 4 points were given when a constant circling activity exceeded 2 turns/min. Animals without any marked asymmetries received a score of 0. Approximately one week after the behavioural tests, the animals were used for acute neurophysiological experiments under ketamine (Ketanest, Parke-Davis, Mfinchen) anaesthesia (duration about 4 h), in the course of which Apo was intravenously injected in a dose of 2 mg/kg (Sontag, Wand, Wolfarth and Osborne, in preparation). At the end of this experiment (1 h after Apo), caudate nuclei of both sides were removed and stored at - - 3 0 °C for further analysis of their D A contents, using the method of Palkovits et al. TM. Differences in the DA content between the right and the left caudate nuclei were statistically analyzed by Student's paired t-test (a
545
DRUG-INDUCED STEREOTYPES AND ASYMMETRIC BEHAVIOUR AFTER SUBSTANTIA NIGRA PARS POSTERIOR (SNPP) LESIONS IN CATS
S. WOLFARTH,E.-F. COELLE,N. N. OSBORNE, K.-H. SONTAG and P. WAND Max-Planck Institute for Experimental Medicine, Department o f Biochemical Pharmacology, HermannRein-Str. 3, D-3400 Goettingen ( G.F.R. ), ( S. IV.) Institute of Pharmacology, Polish Academy of Sciences, 31-343 Krakdw (Poland) and ( N.N.O.) Nuffield Laboratory of Ophthalmology, The University of Oxford, Walton Street, Oxford OX2 6A W (U.K.)
(Accepted March 29th, 1979
SUMMARY Apomorphine- (Apo) and amphetamine- (Amph) induced behavioural phenomena were studied in cats which received either 6-hydroxydopamine (6-OHDA) or electrothermic lesions of the posterior part of the substantia nigra (SNPP). In this species, as in rats, both drugs evoked stereotypies (sniffing and head nodding) and an enhancement of locomotor activity. However, distinct differences between the reactions of cats and rats to both drugs were found, the most evident effect being the lack of sterotyped gnawing and licking. By correlating the data on behaviour, the histological examination showing the size and location of the lesions, and the dopamine (DA) content of the corresponding caudate nuclei, it is concluded that the fewer DA-specific neurons lesioned in the SNPP, the more pronounced was the ipsilateral asymmetric behaviour. We suggest, therefore, that the ipsilateral asymmetric behaviour in cats following Apo- and Amph-treatment is due to the destruction of a non-catecholaminergic output. INTRODUCTION Apomorphine (Apo) and amphetamine (Amph) produce a characteristic behavioural syndrome in rats, known as stereotyped behaviour z,17. In rats with a unilateral lesion of the dopamine (DA) cells of the substantia nigra (SN), the two compounds additionally produce a rotational (asymmetric) behaviour3,~l,zL From these studies, it has been suggested that 6-hydroxydopamine (6-OHDA) lesions of the nigrostriatal pathway result in the dopamine receptors in the neostriatum becoming supersensitive and that Apo injection thereafter causes a rotation away from the lesioned side~L These models of stereotyped and rotational behaviour have been extensively investigated in rats. In contrast to the well-known effects of Apo and Amph
546 in the rat, there is scanty information on the behavioural effects of these drugs in the cat, and no data, to our knowledge, has been published on the action of these agents in cats with lesions of the SN. This lack of information is rather unsatisfactory, as the cat is the animal most commonly used for neurophysiological studies, contributing largely to our understanding of higher nervous system function. Therefore, experiments were designed to compare the effects of both Apo and Amph on cats before and after receiving various types of lesions of the posterior part of SN (SNPP). We chose SNPP, since it has been suggested that this part of SN is involved in mediation of Parkinsonian rigidity via a descending nigro-reticulo-spinal pathway 12. METHODS Experiments were carried out on cats of either sex (approximately 2.5 kg body weight). The lesions were stereotaxically induced 20 under pentobarbital (Nembutal, Abbot) anaesthesia (35 mg/kg i.p.). Cats were divided into 5 groups: Group 1 were sham-operated with stainlesssteel cannulae implanted in both SN (control group); Group 2 received an injection of 1% ascorbic acid only into the right SNPP; Group 3, the right SNPP received 6OHDA (10/~g) dissolved in 1% ascorbic acid while the left SNPP received solvent alone; Group 5, the right SNPP received 6-OHDA (10 #g) dissolved in chilled water and bubbled with N2. The left SNPP received chilled water only. The total volume was 4 #1, which was divided into two 2 #1 portions each being stereotaxically injected into SNPP using two different sets of co-ordinates (A 4.0, L 5.0, H--3.0 and A 2.0, L 4.0, H --3.0); and Group 4, the right SNPP was electrothermically lesioned employing two sets of stereotaxic target co-ordinates (A 4.0, L 3.0, H --5.0 and A 2.0, L 2.0, H --5.5; 45 ° lateral inclination). The tip of the lesion electrode was heated 4 times up to 70 °C for 15 sec (David Kopf Radiofrequency Lesion Maker), twice at the above mentioned stereotaxic target points and twice after the electrode tip was moved 2 mm back. Additionally, the right SNPP of 3 cats received 6-OHDA (10/~g), dissolved in 0.1 ,~Jo ascorbic acid while the left SNPP was injected with 0.1% ascorbic acid only. The speed of the injections was about 0.5/A/min. Cats from the Groups 2-5 were submitted to behavioural tests 12-58 days, 18-21 days, 38-50 days and 66-71 days, respectively, after the lesion in the course of which Amph (D-amphetamine sulfate, E. Merck, Darmstadt; 5 mg/kg i.p.) and Apo (apomorphine hydrochloride, I.C.N. Pharmaceuticals, Eschwege; 2 mg/kg s.c.) were injected. The behavioural effects produced by these drugs were filmed in a 2 × 3 m room (22 °C room temperature). Cats were individually tested and received both compounds at one week intervals. The behavioural phenomena, with the exception of asymmetric behaviour, were scored from 0 to 3 according to their intensity. Mean responses were calculated from 6 different observation periods of individuals cats. Ten minute periods were used for Apo and 20 min periods for Amph, the whole examination period being 60 min for Apo and 120 min for Amph. The scoring of the asymmetric behaviour was as follows.
547
°1
P
Fig. 1. Cannula tracks in formalin-fixed and haematoxylin-stained cross-sections of cat brain in the positions A 4.0 (A) and A 2.0 (B) a0 26 days after injection of 10 #g 6-OHDA in 1% ascorbic acid into the right substantia nigra (arrows) divided into two portions of 2/~1. On the left, only the corresponding solvent volumes were injected. One injection track (A) affected structures of the cerebral peduncle. The diffusion of 6-OHDA should be considered to be of a diameter of 1.5-2.0 mm from the end of the cannula tip.
548 One point was given to an animal which occasionally held its head and neck to one side and turned its body in the same direction; 2 points were given when the head and neck were consistently held to one side (this was associated with a body twist to the same side and occasional spontaneous circling behaviour in the same direction); 3 points, when periods of spontaneous circling activity (head-to-tail) were present but did not exceed 2 turns/min; and 4 points were given when a constant circling activity exceeded 2 turns/min. Animals without any marked asymmetries received a score of 0. Approximately one week after the behavioural tests, the animals were used for acute neurophysiological experiments under ketamine (Ketanest, Parke-Davis, Mfinchen) anaesthesia (duration about 4 h), in the course of which Apo was intravenously injected in a dose of 2 mg/kg (Sontag, Wand, Wolfarth and Osborne, in preparation). At the end of this experiment (1 h after Apo), caudate nuclei of both sides were removed and stored at - - 3 0 °C for further analysis of their D A contents, using the method of Palkovits et al. TM. Differences in the DA content between the right and the left caudate nuclei were statistically analyzed by Student's paired t-test (a
