Pharmacology Biochemistry & Behavior, Vol. 4, pp. 347-349. Copyright © 1976 by ANKHO International Inc. All rights of reproduction in any form reserved. Printed in the U.S.A.
BRIEF COMMUNICATION Comparison in Mice of the Amnestic Effects of Cycloheximide and 6-Hydroxydopamine in a One-Trial Passive Avoidance Task I THOMAS C. RAINBOW, JOSHUA E. A D L E R AND LOUIS B. F L E X N E R
Department o f Anatomy and Institute o f Neurological Sciences School o f Medicine, Univeristy o f Pennsylvania, Philadelphia, PA 191 74 (Received 19 August 1975) RAINBOW, T. C., J. E. ADLER AND L. B. FLEXNER. Comparison in mice of the amnestic effects ofcycloheximide and 6-hydroxydopamine in a one-trial passive avoidance task. PHARMAC. BIOCHEM. BEHAV. 4(3) 347-349, 1976. - To test further the hypothesis that cycloheximide (CXM)-induced amnesia is due in part to its effects on the central adrenergic system, a comparison was made in mice of the effects of the antibiotic and of 6-hydroxydopamine (6-OHDA) on memory of a one-trial passive avoidance task. Both drugs produced amnesia 24 hr after training but unlike CXM, 6-OHDA had no effect on memory 20 rain after training. Cycloheximide
6-Hydroxydopamine
Amnesia
METHOD
T R A I N I N G in the presence of cycloheximide (CXM), an inhibitor of protein synthesis, results in loss of memory in several training situations [7, 1 1, 17]. While the amnestic effects of CXM are often attributed solely to inhibition o f protein synthesis, there is increasing evidence that it has side effects on the adrenergic system and that these side effects may contribute importantly to the amnesia. Thus the loss o f memory induced by the antibiotic and its analog, acetoxycycloheximide, is prevented by treatment with adrenergic stimulants [3,16] or monoamine oxidase inhibitors [4]. Both antibiotics cause a loss of tyrosine hydroxylase activity [6,18], both decrease the rate of synthesis of norepinephrine (NE) and dopamine (DA), and both cause an increase in levels of NE and DA (in spite of a depressed rate o f synthesis) suggesting additional modifications of catecholamine (CA) metabolism [5,8]. T h e severe, chronic central adrenergic denervation caused by 6-hydroxydopamine (6-OHDA) offers an opportunity to evaluate directly the role of the adrenergic system in memory. If CXM affects only the adrenergic system one might anticipate that its effects would be reproduced in animals treated with 6-OHDA. We have found that, like CXM, t h e chronic central denervation produced by 6-OHDA results in amnesia for a one-trial passive avoidance response at 24 hr. Unlike CXM, however, 6-OHDA has no significant effect on memory shortly after training.
Male C 5 7 b l / 6 J mice were housed 4 to a cage in a soundp r o o f room at 24.5 ° artifically lighted from 7 a.m. to 7 p.m. Food and water were ad lib. U n d e r Nembutal anesthesia (75 mg/kg), 25 #g of 6-OHDA HBr (Regis) in 5 ul of saline containing 0.1% ascorbic acid was injected into each lateral ventricle. Control mice were injected in the same way with ascorbic acid vehicle. Mice were then isolated for at least 2 weeks before being used for behavioral or biochemical studies. By the end o f the first week, cage behavior, feeding and drinking appeared normal. Postoperative mortality of mice treated with 6-OHDA was 10%. CXM ( 1 2 0 m g / k g ) was injected subcutaneously 30 min before training. For the CA assays on the cerebral hemispheres, mice were killed by cervical dislocation. CAs were extracted and NE assayed according to the method of Anton and Sayre [2] as modified by Moore and Smith [10]. DA was assayed as described by Adler [ 1 ]. The two-compartment passive avoidance box was identical to that described by Randt etal. [14]. Mice were placed in the small compartment of the box 40 sec before the door was opened to the large compartment. After entering, the door was closed and 5sec later a 0 . 1 6 m A scrambled foot shock lasting 2 sec was automatically given. Mice were removed immediately to their home cages and
' This work was supported by National Science Foundation Research Grant GB-42753. 347
348
RAINBOW, ADLER AND FLEXNER
180--
"~
150--
+1
120. ¢13 ¢--
~" e--
90-
g ~.
30-
lreatment
SAL
SAL
VEH
VEH
CXM
6-OHDA CXM
Hrafter training
0.3 24
24
0.3
0.3
0.3
24
60HDA
24
FIG. 1. Effects of treatment with CXM and 6-OHDA on memory of one-trial passive avoidance task 20 min and 24 hr after training. P values (Mann-Whitney U-test, 1-tailed): Saline 24 hr (n = 9) vs vehicle 24 hr (n = 9) 0.1; CXM 0.3 hr (n = 4) vs saline 0.3 hr (n = 5) --- 0.008; 6-OHDA 0.3 hr (n = 5) vs vehicle 0.3 hr (n = 5) = 0.1 ; CXM 24 hr (n = 9) vs saline 24 hr = 0.001 ; 6-OHDA 24 hr (n = 9) vs vehicle 24 hr = 0.001. S.E.M. --- standard error of the median.
t e s t e d for r e t e n t i o n 20 rain or 24 h r later. L a t e n c y t o e n t e r was t a k e n as t h e t i m e b e t w e e n o r i e n t a t i o n t o w a r d s t h e large c o m p a r t m e n t a n d t h e t i m e w h e n all paws were o n t h e bars o f t h e large c o m p a r t m e n t . A m a x i m u m interval of 30 sec was allowed for o r i e n t a t i o n . Mice t h a t failed t o e n t e r t h e large c o m p a r t m e n t w i t h i n 3 rain were r e m o v e d a n d given a score o f 3 rain. RESULTS
(aJ Biochemical T h e m e a n s -+ SEM for c e r e b r a l NE and DA of t h e controis (n = 7) were 0.29 -+ 0.02 a n d 1.06 + 0.07 #g/g, respectively, u n c o r r e c t e d for 70% recovery. T h e m e a n s + SEM for NE a n d DA a f t e r t r e a t m e n t w i t h 6 - O H D A o n e day a f t e r t h e b e h a v i o r a l e x p e r i m e n t s were, respectively, 0.05 +- 0.03 a n d 0.31 + 0.05 ug/g. T h u s 6 - O H D A r e d u c e d t h e average level of N E b y 83% a n d t h a t o f D A b y 71%.
(b) Behavioral As s h o w n in Fig. I, CXM p r o d u c e d m a r k e d a m n e s i a b o t h at 20 rain (n = 4) a n d 24 h r ( n = 9) a f t e r training. By c o n t r a s t , t r e a t m e n t w i t h 6 - O H D A h a d n o significant effect o n m e m o r y at 20 rain (n = 5) b u t , like CXM, caused severe amnesia at 24 h r ( n = 9). DISCUSSION AS s t a t e d above, t h e r e is evidence t h a t can be i n t e r p r e t e d
to m e a n t h a t C X M - i n d u c e d a m n e s i a results in part f r o m i n t e r f e r e n c e with t h e central adrenergic system. T o test this possibility f u r t h e r , we have c o m p a r e d C X M - i n d u c e d a m n e s i a o f a one-trial passive a v o i d a n c e task t o t h a t o b s e r v e d in mice t h a t h a d a drastic loss of CAs a f t e r treatm e n t w i t h 6-OHDA. T h e t w o a m n e s i a s were b o t h severe at 24 hr. T w e n t y m i n u t e s a f t e r training, h o w e v e r , t h o s e mice t r e a t e d w i t h 6 - O H D A h a d a h i g h level of m e m o r y ; t h o s e with C X M , p r o f o u n d a m n e s i a as also o b s e r v e d by Q u a r t e r m a i n a n d M c E w e n [ 12] a n d s h o w n n o t t o be d u e to effects o n activity [ 9 ] , R e t e n t i o n of m e m o r y at 20 m i n w i t h 6 - O H D A i n d i c a t e s n o r m a l a c q u i s i t i o n ; a m n e s i a at 24 h r suggests a failure o f f u r t h e r c o n s o l i d a t i o n or a failure o f retrieval. T h a t failure o f retrieval r a t h e r t h a n of a c q u i s i t i o n does o c c u r w i t h CXM has b e e n s h o w n b y r e c o v e r y o f m e m o r y following t r e a t m e n t w i t h m o n o a m i n e oxidase i n h i b i t o r s [41 or n o n c o n t i n g e n t s h o c k s [ 11 ]. The meaning of the difference between the two groups at 20 m i n after t r a i n i n g is obscure. C o m p a t i b l e w i t h o u r results are t h o s e o f R a n d t et al. [ 15] a n d Z o r n e t z e r et al. [ 19] w h o f o u n d r e t e n t i o n o f m e m o r y of a one-trial passive a v o i d a n c e task for a s h o r t t i m e a f t e r t r a i n i n g t h a t was c o n d u c t e d in t h e p r e s e n c e o f a n i n h i b i t o r o f DA-flhydroxylase or o f t y r o s i n e h y d r o x y l a s e . The early a m n e s i a a f t e r CXM suggests t h a t its effects o n t h e c e n t r a l n e r v o u s s y s t e m differ f r o m t h o s e of 6 - O H D A and t h e i n h i b i t o r s of CA synthesis. This d i f f e r e n c e m a y involve o n l y t h e adrenergic s y s t e m or m a y be due to i n t e r f e r e n c e w i t h o t h e r aspects o f neuronal function.
CYCLOHEXIMIDE 6-HYDROXYDOPAMINE AND AMNESIA
349
REFERENCES 1. Adler, J. E. The effect of chronic central adrenergic denervation on learning and memory of an aversive discrimination task in m i c e : studies with 6-hydroxydopamine. Unpublished doctoral dissertation, University of Pennsylvania, 1975. 2. Anton, A. H. and D. F. Sayre. A study of the factors affecting the aluminum oxide trihydroxyindole procedure for the analysis of catecholamines. J. Pharmac. exp. Ther. 138: 360-375, 1962. 3. Barondes, S. H. and H. D. Cohen. Arousal and the conversion of "short-term" to "long-term" memory. Proc. natn. Acad. Sci., U.S.A. 58: 157-162, 1967. 4. Botwinick, C. Y. and D. Quartermain. Recovery from amnesia induced by pre-test injections of monoamine oxidase inhibitors. Pharrnac. Biochem. Behav. 2: 375-379, 1974. 5. Flexner, L. B. and R. H. Goodman. Studies on memory: Inhibitors of protein synthesis also inhibit catecholamine synthesis. Proc. natn. Acad. Sci., U.S.A., 72: 4 6 6 0 - 4 6 6 9 , 1975. 6. Flexner, L. B., R. G. Scrota and R. H. Goodman. "Cycloheximide and acetoxycycloheximide: inhibition of tyrosine hydroxylase activity and amnestic effects. Proc. hath. Acad. Sci., U.S.A. 70: 354-356, 1973. 7. Flood, J. L., M. R. Rosenzweig, E. C. Bennett and A. E. Orme. Influence of training strength on amnesia induced by pretraining injections of cycloheximide. Physiol. Behav. 9: 5 8 9 - 6 0 0 , 1973. 8. Goodman, R. H., J. B. Flexner and L. B. Flexner. The effect of acetoxycycloheximide on rate of accumulation of cerebral catecholamines from circulating tyrosine as related to its effect on memory. Proc. natn. Acad. Sci., U.S.A. 72: 4 7 9 - 4 8 2 , 1975. 9. Gutwein, B., D. Quartermain and B. S. McEwen. Dissociation of cycloheximide's effects on activity from its effects on memory. Pharmac. Biochem. Behav. 2: 7 5 3 - 7 5 6 , 1974.
10. Moore, R. Y. and R. A. Smith. Potential development of a norepinephfine response to light in the rat pineal and salivary glands. Neuropharmacology 10: 315-323, 1971. 11. Quartermain, D. and C. Y. Botwinick. The role of the biogenic amines in the reversal of cycloheximide-induced amnesia. J. comp. physiol. Psychol. 88: 386-401, 1975. 12. Quartermain, D. and B. S. McEwen. Temporal characteristics of amnesia induced by protein synthesis inhibitor: determination by shock level. Nature 228: 6 7 7 - 6 7 8 , 1970. 13. Quartermain, D., B. S. McEwen and E. C. Azmitia. Amnesia produced by cycloheximide: conditions for recovery. Science 169: 6 8 3 - 6 8 6 , 1970. 14. R a n d t , C. T., B. M. Barnett, B. S. McEwen and D. Quartermain. Amnestic effects of cycloheximide on two strains of mice with different memory characteristics. Expl Neurol. 30: 4 6 7 - 4 7 4 , 1971. 15. Randt, C. T., D. Quartermain, M. Goldstein and B. Anagnoste. Norepinephrine biosynthesis inhibition: effects on memory in mice. Science 172: 4 9 8 - 4 9 9 , 1971. 16. Serota, R. G., R. B. Roberts and L. B. Flexner. Acetoxycycloheximide-induced transient amnesia: protective effects of adrenergic stimulants. Proc. natn. Acad. Sct, U.S.A. 64: 340-342, 1972. 17. Squire, L. R. and S. H. Barondes. Variable decay of memory and its recovery in cycloheximide treated mice. Proc. natn. Acad. Sct, U.S.A. 69: 1416-1420, 1972. 18. Squire, L. R., R. Kuczenski and S. H. Barondes. Tyrosine hydroxylase inhibition by cycloheximide and anisomycin is not responsible for their amnestic effects. Brain Res. 82: 241-248, 1974. 19. Zornetzer, S. F., M. S. Gold and J. Hendrickson. Alpha-methylp-tyrosine and memory: state-dependency and memory failure. Behav. Biol. 12: 135-141, 1974.
BRIEF COMMUNICATION Comparison in Mice of the Amnestic Effects of Cycloheximide and 6-Hydroxydopamine in a One-Trial Passive Avoidance Task I THOMAS C. RAINBOW, JOSHUA E. A D L E R AND LOUIS B. F L E X N E R
Department o f Anatomy and Institute o f Neurological Sciences School o f Medicine, Univeristy o f Pennsylvania, Philadelphia, PA 191 74 (Received 19 August 1975) RAINBOW, T. C., J. E. ADLER AND L. B. FLEXNER. Comparison in mice of the amnestic effects ofcycloheximide and 6-hydroxydopamine in a one-trial passive avoidance task. PHARMAC. BIOCHEM. BEHAV. 4(3) 347-349, 1976. - To test further the hypothesis that cycloheximide (CXM)-induced amnesia is due in part to its effects on the central adrenergic system, a comparison was made in mice of the effects of the antibiotic and of 6-hydroxydopamine (6-OHDA) on memory of a one-trial passive avoidance task. Both drugs produced amnesia 24 hr after training but unlike CXM, 6-OHDA had no effect on memory 20 rain after training. Cycloheximide
6-Hydroxydopamine
Amnesia
METHOD
T R A I N I N G in the presence of cycloheximide (CXM), an inhibitor of protein synthesis, results in loss of memory in several training situations [7, 1 1, 17]. While the amnestic effects of CXM are often attributed solely to inhibition o f protein synthesis, there is increasing evidence that it has side effects on the adrenergic system and that these side effects may contribute importantly to the amnesia. Thus the loss o f memory induced by the antibiotic and its analog, acetoxycycloheximide, is prevented by treatment with adrenergic stimulants [3,16] or monoamine oxidase inhibitors [4]. Both antibiotics cause a loss of tyrosine hydroxylase activity [6,18], both decrease the rate of synthesis of norepinephrine (NE) and dopamine (DA), and both cause an increase in levels of NE and DA (in spite of a depressed rate o f synthesis) suggesting additional modifications of catecholamine (CA) metabolism [5,8]. T h e severe, chronic central adrenergic denervation caused by 6-hydroxydopamine (6-OHDA) offers an opportunity to evaluate directly the role of the adrenergic system in memory. If CXM affects only the adrenergic system one might anticipate that its effects would be reproduced in animals treated with 6-OHDA. We have found that, like CXM, t h e chronic central denervation produced by 6-OHDA results in amnesia for a one-trial passive avoidance response at 24 hr. Unlike CXM, however, 6-OHDA has no significant effect on memory shortly after training.
Male C 5 7 b l / 6 J mice were housed 4 to a cage in a soundp r o o f room at 24.5 ° artifically lighted from 7 a.m. to 7 p.m. Food and water were ad lib. U n d e r Nembutal anesthesia (75 mg/kg), 25 #g of 6-OHDA HBr (Regis) in 5 ul of saline containing 0.1% ascorbic acid was injected into each lateral ventricle. Control mice were injected in the same way with ascorbic acid vehicle. Mice were then isolated for at least 2 weeks before being used for behavioral or biochemical studies. By the end o f the first week, cage behavior, feeding and drinking appeared normal. Postoperative mortality of mice treated with 6-OHDA was 10%. CXM ( 1 2 0 m g / k g ) was injected subcutaneously 30 min before training. For the CA assays on the cerebral hemispheres, mice were killed by cervical dislocation. CAs were extracted and NE assayed according to the method of Anton and Sayre [2] as modified by Moore and Smith [10]. DA was assayed as described by Adler [ 1 ]. The two-compartment passive avoidance box was identical to that described by Randt etal. [14]. Mice were placed in the small compartment of the box 40 sec before the door was opened to the large compartment. After entering, the door was closed and 5sec later a 0 . 1 6 m A scrambled foot shock lasting 2 sec was automatically given. Mice were removed immediately to their home cages and
' This work was supported by National Science Foundation Research Grant GB-42753. 347
348
RAINBOW, ADLER AND FLEXNER
180--
"~
150--
+1
120. ¢13 ¢--
~" e--
90-
g ~.
30-
lreatment
SAL
SAL
VEH
VEH
CXM
6-OHDA CXM
Hrafter training
0.3 24
24
0.3
0.3
0.3
24
60HDA
24
FIG. 1. Effects of treatment with CXM and 6-OHDA on memory of one-trial passive avoidance task 20 min and 24 hr after training. P values (Mann-Whitney U-test, 1-tailed): Saline 24 hr (n = 9) vs vehicle 24 hr (n = 9) 0.1; CXM 0.3 hr (n = 4) vs saline 0.3 hr (n = 5) --- 0.008; 6-OHDA 0.3 hr (n = 5) vs vehicle 0.3 hr (n = 5) = 0.1 ; CXM 24 hr (n = 9) vs saline 24 hr = 0.001 ; 6-OHDA 24 hr (n = 9) vs vehicle 24 hr = 0.001. S.E.M. --- standard error of the median.
t e s t e d for r e t e n t i o n 20 rain or 24 h r later. L a t e n c y t o e n t e r was t a k e n as t h e t i m e b e t w e e n o r i e n t a t i o n t o w a r d s t h e large c o m p a r t m e n t a n d t h e t i m e w h e n all paws were o n t h e bars o f t h e large c o m p a r t m e n t . A m a x i m u m interval of 30 sec was allowed for o r i e n t a t i o n . Mice t h a t failed t o e n t e r t h e large c o m p a r t m e n t w i t h i n 3 rain were r e m o v e d a n d given a score o f 3 rain. RESULTS
(aJ Biochemical T h e m e a n s -+ SEM for c e r e b r a l NE and DA of t h e controis (n = 7) were 0.29 -+ 0.02 a n d 1.06 + 0.07 #g/g, respectively, u n c o r r e c t e d for 70% recovery. T h e m e a n s + SEM for NE a n d DA a f t e r t r e a t m e n t w i t h 6 - O H D A o n e day a f t e r t h e b e h a v i o r a l e x p e r i m e n t s were, respectively, 0.05 +- 0.03 a n d 0.31 + 0.05 ug/g. T h u s 6 - O H D A r e d u c e d t h e average level of N E b y 83% a n d t h a t o f D A b y 71%.
(b) Behavioral As s h o w n in Fig. I, CXM p r o d u c e d m a r k e d a m n e s i a b o t h at 20 rain (n = 4) a n d 24 h r ( n = 9) a f t e r training. By c o n t r a s t , t r e a t m e n t w i t h 6 - O H D A h a d n o significant effect o n m e m o r y at 20 rain (n = 5) b u t , like CXM, caused severe amnesia at 24 h r ( n = 9). DISCUSSION AS s t a t e d above, t h e r e is evidence t h a t can be i n t e r p r e t e d
to m e a n t h a t C X M - i n d u c e d a m n e s i a results in part f r o m i n t e r f e r e n c e with t h e central adrenergic system. T o test this possibility f u r t h e r , we have c o m p a r e d C X M - i n d u c e d a m n e s i a o f a one-trial passive a v o i d a n c e task t o t h a t o b s e r v e d in mice t h a t h a d a drastic loss of CAs a f t e r treatm e n t w i t h 6-OHDA. T h e t w o a m n e s i a s were b o t h severe at 24 hr. T w e n t y m i n u t e s a f t e r training, h o w e v e r , t h o s e mice t r e a t e d w i t h 6 - O H D A h a d a h i g h level of m e m o r y ; t h o s e with C X M , p r o f o u n d a m n e s i a as also o b s e r v e d by Q u a r t e r m a i n a n d M c E w e n [ 12] a n d s h o w n n o t t o be d u e to effects o n activity [ 9 ] , R e t e n t i o n of m e m o r y at 20 m i n w i t h 6 - O H D A i n d i c a t e s n o r m a l a c q u i s i t i o n ; a m n e s i a at 24 h r suggests a failure o f f u r t h e r c o n s o l i d a t i o n or a failure o f retrieval. T h a t failure o f retrieval r a t h e r t h a n of a c q u i s i t i o n does o c c u r w i t h CXM has b e e n s h o w n b y r e c o v e r y o f m e m o r y following t r e a t m e n t w i t h m o n o a m i n e oxidase i n h i b i t o r s [41 or n o n c o n t i n g e n t s h o c k s [ 11 ]. The meaning of the difference between the two groups at 20 m i n after t r a i n i n g is obscure. C o m p a t i b l e w i t h o u r results are t h o s e o f R a n d t et al. [ 15] a n d Z o r n e t z e r et al. [ 19] w h o f o u n d r e t e n t i o n o f m e m o r y of a one-trial passive a v o i d a n c e task for a s h o r t t i m e a f t e r t r a i n i n g t h a t was c o n d u c t e d in t h e p r e s e n c e o f a n i n h i b i t o r o f DA-flhydroxylase or o f t y r o s i n e h y d r o x y l a s e . The early a m n e s i a a f t e r CXM suggests t h a t its effects o n t h e c e n t r a l n e r v o u s s y s t e m differ f r o m t h o s e of 6 - O H D A and t h e i n h i b i t o r s of CA synthesis. This d i f f e r e n c e m a y involve o n l y t h e adrenergic s y s t e m or m a y be due to i n t e r f e r e n c e w i t h o t h e r aspects o f neuronal function.
CYCLOHEXIMIDE 6-HYDROXYDOPAMINE AND AMNESIA
349
REFERENCES 1. Adler, J. E. The effect of chronic central adrenergic denervation on learning and memory of an aversive discrimination task in m i c e : studies with 6-hydroxydopamine. Unpublished doctoral dissertation, University of Pennsylvania, 1975. 2. Anton, A. H. and D. F. Sayre. A study of the factors affecting the aluminum oxide trihydroxyindole procedure for the analysis of catecholamines. J. Pharmac. exp. Ther. 138: 360-375, 1962. 3. Barondes, S. H. and H. D. Cohen. Arousal and the conversion of "short-term" to "long-term" memory. Proc. natn. Acad. Sci., U.S.A. 58: 157-162, 1967. 4. Botwinick, C. Y. and D. Quartermain. Recovery from amnesia induced by pre-test injections of monoamine oxidase inhibitors. Pharrnac. Biochem. Behav. 2: 375-379, 1974. 5. Flexner, L. B. and R. H. Goodman. Studies on memory: Inhibitors of protein synthesis also inhibit catecholamine synthesis. Proc. natn. Acad. Sci., U.S.A., 72: 4 6 6 0 - 4 6 6 9 , 1975. 6. Flexner, L. B., R. G. Scrota and R. H. Goodman. "Cycloheximide and acetoxycycloheximide: inhibition of tyrosine hydroxylase activity and amnestic effects. Proc. hath. Acad. Sci., U.S.A. 70: 354-356, 1973. 7. Flood, J. L., M. R. Rosenzweig, E. C. Bennett and A. E. Orme. Influence of training strength on amnesia induced by pretraining injections of cycloheximide. Physiol. Behav. 9: 5 8 9 - 6 0 0 , 1973. 8. Goodman, R. H., J. B. Flexner and L. B. Flexner. The effect of acetoxycycloheximide on rate of accumulation of cerebral catecholamines from circulating tyrosine as related to its effect on memory. Proc. natn. Acad. Sci., U.S.A. 72: 4 7 9 - 4 8 2 , 1975. 9. Gutwein, B., D. Quartermain and B. S. McEwen. Dissociation of cycloheximide's effects on activity from its effects on memory. Pharmac. Biochem. Behav. 2: 7 5 3 - 7 5 6 , 1974.
10. Moore, R. Y. and R. A. Smith. Potential development of a norepinephfine response to light in the rat pineal and salivary glands. Neuropharmacology 10: 315-323, 1971. 11. Quartermain, D. and C. Y. Botwinick. The role of the biogenic amines in the reversal of cycloheximide-induced amnesia. J. comp. physiol. Psychol. 88: 386-401, 1975. 12. Quartermain, D. and B. S. McEwen. Temporal characteristics of amnesia induced by protein synthesis inhibitor: determination by shock level. Nature 228: 6 7 7 - 6 7 8 , 1970. 13. Quartermain, D., B. S. McEwen and E. C. Azmitia. Amnesia produced by cycloheximide: conditions for recovery. Science 169: 6 8 3 - 6 8 6 , 1970. 14. R a n d t , C. T., B. M. Barnett, B. S. McEwen and D. Quartermain. Amnestic effects of cycloheximide on two strains of mice with different memory characteristics. Expl Neurol. 30: 4 6 7 - 4 7 4 , 1971. 15. Randt, C. T., D. Quartermain, M. Goldstein and B. Anagnoste. Norepinephrine biosynthesis inhibition: effects on memory in mice. Science 172: 4 9 8 - 4 9 9 , 1971. 16. Serota, R. G., R. B. Roberts and L. B. Flexner. Acetoxycycloheximide-induced transient amnesia: protective effects of adrenergic stimulants. Proc. natn. Acad. Sct, U.S.A. 64: 340-342, 1972. 17. Squire, L. R. and S. H. Barondes. Variable decay of memory and its recovery in cycloheximide treated mice. Proc. natn. Acad. Sct, U.S.A. 69: 1416-1420, 1972. 18. Squire, L. R., R. Kuczenski and S. H. Barondes. Tyrosine hydroxylase inhibition by cycloheximide and anisomycin is not responsible for their amnestic effects. Brain Res. 82: 241-248, 1974. 19. Zornetzer, S. F., M. S. Gold and J. Hendrickson. Alpha-methylp-tyrosine and memory: state-dependency and memory failure. Behav. Biol. 12: 135-141, 1974.
