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LSD: permanent behavioral effect in rats
European Journal of Phannacologj,, 147 (1988) 309-311
309
Elsevier EIP 20083 Short commnnle_~don
LSD: permanent beha or d effect in rats Peter B. Silverman Department of Psychiatry and Behavioral Sciences, Universityof Texas Medical School at Houston, 1300 Moursun~ Houston, TX 77030, U.S.A.
Received10 December1987,accepted 12 January1988
Rats with a unilateral nigrostaiatal lesion produced by infusion of 6-hydro~--~jdopamine(6-OHDA) exhib/ted acute contralateral (apomorphine-like) rotation in response to systemic LSD administration. When re-introduced to the environment in which LSD had been administered weeks earlier, the animals exhibited a 2-3 rain burst of contralateral rotation. This behavior developed over a period of weeks and could be produced by a single LSD treatment. latent, undrugged rotation is similar to that which we previously reported to result from one or more apomorphine treatments. LSD; Dopamine receptor agonists; Rotational behavior
I. Introduction Rats with unilateral lesions of the nigrostriatal system rotate (turn in circles) in response to challenge with dopamine (DA) receptor agonists (Ungerstedt, 1971). Indirect acting DA receptor agonists (e.g. amphetamine, cocaine) induce ipsilateral circling which has been attributed to DA release/reuptake inhibition occurring only in the intact hemisphere. Direct acting DA receptor agonists, e.g. apomorphine, induce contralaterally directed circling, presumably reflecting denervation supersensitivity in the lesioned striatmn. Pieri et al. (1974) demonstrated that the potent hallucinogen, LSD, acts as a direct DA receptor agonist in this animal preparation. We previously reported that lesioned rats administered a single small dose of apomorphine exhibited a striking, persistent change in behavior (Silverman and Ho, 1981). When placed in the environment in which the single apomorphine treatment had been given, the rats burst into intense contralateral rotation. This brief period of rotation was demonstrable throughout the lifetime of the animals. The behavior had some characteristics of 'simple' associative
learning, e.g. stimulus (environmental) specificity, but other characteristics that m acle it seem anything but simple. For example, low doses were more effective than larger doses in inducing the behavior and there was no recency effect (it took 2 weeks from drug treatment to undrugged test for the behavior to be fufiy expressed). The p~h-pose of the work presented here was to determine ff LSD, a compound that is different from apomorphine in many respects, but which shares the acute rotational effect in m'grostriatally lesioned rats (Pieri et al., 1974), resulted in a longterm behavioral effect similar to that of apomorphine.
2. Materials and methods Male Sprague-Dawley rats (Simon:e~, Gilroy, CA) w~ghi~g 180-240 g were anesthegzed with 40 mg/kg pentobarbital and mounted in a stereotaxic device. A lesion was produced by infusion of 4 /tl of saline containing 0.1~; ascorbate and 2 ~tg//zl (base weight) 6-hydroxydopamine (6OHDA) HBr. Stereotaxic coordinates, with incisor
0014-2999/88/$03.50 © 1988 ElsevierScience Publishers B.V.(BiomedicalDivision)
3~0 bar at ~ , were 1.4 L and 4.2 P from bregma, 8 mm ventr~ from the sku]l surface. The 6-OHDA sohltion was administered at 0.33 p l / m i n via syringe pump, 10 pl syringe, PE 10 tubing and 27 gauge Observations of rotational behavior were made in 26 cm ~ t e r d e a r plastic bowls. Complete 360 ° tams made in 3 ndn ob.q:rvation periods immediately prior to, and immediately after, drug injection and at 15 rain intervals thereafter were ~tecL Subsequent ~ t i o n s of undrugged behavior consisted solely of 3 rain observation begi'nning immediately after the animal was placed in the bowl. During the intervals betweea drug tests and undrugged Observations, rats remained undisturbed in their home cages with ad lib food and water throughout. LSD tartrate (NIDA) was administered i.p. in I m l / k g saline. Animals in Group 1 ( n - - 5 ) were utilized to determine the appropriate doses of LSD to be used in future rotation experiments. They were treated with 50 ~g/'~g LSD four times, 100/xg/kg once and 200/~g/lrg twice. All these drug treatmerits were administered between 2 and 4 weeks after the rats were lesioned. They were subsequently placed in the rotation bowls for 3 rain observations with no further drug treatment at intervals up to 24 weeks after lesion. Group 2 animals (n----4) were treated with 100 ~&/kg LSD once at 4 weeks and again at 6 weeks after being lesioned. Undrugged observations were then made up to 20 weeks after lesion. Group 3 animals ( n - 5) were treated with a sing]e dose of 200 p g / k g LSD at 2 weeks post-lesion. They were observed undrugged at 4 and 8 weeks post-lesion.
3. Rese]ts The ~ t s , summarized in table 1, show that aU groups of animals exhibited, on the average, a sl/ght ips/l~teral bias prior to any drug treatment. Group i animals, which got 50 to 200 ~tg/kg LSD on several occasions, all showed contralateral rotat/on m r - ~ .nse to one or more of the LSD doses. When reintroduced to the rotation environment weeks or months after the last drug treat-
TABLE 1 Undrugged rotational response (X+ S.E.M. contralateral turns/3 rain) upon exposure to the rotation environment prior to, and at various times after, LSD treatment. Negativescores indicate net ipsilateral turns. Group (n) 1(5)
2(4)
Undrusgedresponse Treatment (weeks post-lesion) (weekspost-lesion) -5.0+ 0.4 (2) a 50-2001tg/kgLSD(2-4) 15.6+ 9.1 (6) 44.0-1-12.8 (8) 46.0+ 7.1 (13) 29.8+ 7.2(18) 26.4+ 7.1(24) -1.0+ 0.8 (4) a 0.5 + 0.3 (6)" 4.8+ 8.5± 23.8+
2.9 (8) 6.8(11)
7.8(15) 20.55: 9.5(20) 3(5)
-2.8+ 0.4 (2)" 15.4+ 2.4 (4) 23.6:1:7.0 (8)
1001tg/kgLSD(4) 100 pg/kg LSD (6) -
200/tg/kgLSD(2) -
a Undrugged tests which were followedby the indicated treatmeat(s).
merit, these animals exhibited rapid contralateral rotation. The peak of undrugged rotation was observed at 13 weeks after lesion (9 weeks after the last drug treatment), and a clear response was still apparent 24 weeks post-lesion (20 weeks post-drug). Group 2 animals showed peak acute responses to their two treatments with 100 # g / k g LSD of 25.5 + 10.4 and 39.2 d: 10.8 ~ + S.E.M. turns/3 rain), respectively. In both cases the peak rates were observed in the bin from 15-18 min after injection. Rotation had essentially stopped by the 45-48 rain bin. They showed a shift in the direction of undrugged bias 2 weeks after the first 100 /~g/kg LSD treatment, but not the high speed latent rotational behavior. This behavior did appear after the second drug treatment and became more pronounced with the passage of time. Animals in Group 3, given a single t r e a t m e n t with 200 t t g / k g LSD, exhibited acute contralateral rotation averaging 38.4_-k 4.5 turns/3 rain with the peak rate again observed in the bin beginning 15 rain after injection. Rotation lasted
311
about 45 rain. When placed, undrugged, in the rotation bowls weeks later, they exhibited the rapid contrallateral rotation. One animal from this group died prior to an observation made 20 weeks after the lesion (18 weeks after drug treatment); the other four all still exhibited the behavior.
4. Discussion Ungerstedt (1971; 1976) described an unusual behavior in rats that had been nigrostriatally lesioned with 6-OHDA. Some time after being lesioned, the undrugged animals would show 'explosive' contralateral rotation at the beginning of experimental sessions. Ungerstedt termed this strange behavior 'paradoxical' rotation. We subsequently demonstrated (Si!verman and Ho, 1981) that paradoxical rotation was not a consequence of lesion alone, but the result of prior drug treatment. Lesioned but drug naive animals never demonstrated the behavior, but those that had received even a single apomorphine treatment did so months after the treatment (we tested up to one year after treatment). Rats that had been treated several times with apomorphine displayed marked contralateral rotation and, in many instances, full blown stereotypy when reintroduced to the drug environment. Recently Burunat et al. (1987) have replicated some of our findings using multiple apomorphine administrations. EmphasiTing the role of learning, they pointed out that the rate of rotation in the first minute after the last treatment with apomorphine correlated highly with subsequent undrugged rotation. This relationship does not hold true for the single treatment situation in the case of either apomorphine or LSD. In the first minute after treatment with either of these compounds for the first (and only) time, the animals rotate, if at all, one or two times ipsilaterally. In the single dose case, there does seem to be a positive correlation betweea the peak rate acutely after drug and subsequent undrugged rotation (unpublished observation). The undrugged rotation in some cases exceeds that ever observed while the animal is drugged. Further, in the case of apomorphine this relationship holds only when animals treated with the same single dose are
compared. Larger doses of apomorphine resulted in the same peak rate (but for a period of time) resulted in less subsequent undrugged rotation. One of the remarkable features of latent rotation after a single apomorphine treatment was that the behavior showed no recency effect; it became more robust with the passage of time to 2 weeks after drug treatment, by which time the maximum effect had been reached (Silverman and Ho, 1981). Although not examined as systematically, there appears to be a similar, perhaps longer, 'incubation periods' for LSD-induced latent rotation. Apomorphine-induced latent rotation also showed a peculiar dose response effect in that 50 /tg/kg was a more efficacious dose than 0.25 or 1.0 mg/kg. With LSD, on the other hand, latent rotation was observed 2 weeks after a single dose of 200/tg/kg but not 2 weeks after 100 ~g/kg. Perhaps a single 100/tg/kg dose would have been effective after a longer waiting period. The data presented here show that LSD as well as apomorphine induces a permanent behavioral effect after a single treatment. There is a great deal of current interest in the phenomenon of drug sensitization, i.e. increased response to repeated drug administrations. The undrugged rotational response to apomorphine and LSD would seem to represent the ultimate in context-dependent ~%~!sitization in that it develops after a single dose and is demonstrable without subsequent drug administration.
References Burunat, E., M.D. Diaz-Palarea, R. Castro and M. Rodriguez, 1987, Undmgged rotational response in nigro-striatal system-lesioned rats is related to the previous early response to apomorphine when repeatedly administered, Life St,i. 41, 309. Pieri, L., L. Pieri and W. Haefely, 1974, LSD as an agonist of dopamine receptors in the striatum, Nature 252, 586. Silverman, P.B. and B.T. Ho, 1981, Persistent behavioral effect of apomorphine in 6-hydroxydomaine-lesioned rats, Nature 294, 475. Ungerstedt, U., 1971, Striatal dopamine release after amphetamine or nerve degeneration revealed by rotational behavior, Acta Physiol. Scand. (SuppL) 367, 49. Ungerstedt, U., 1976, 6-Hydroxydopamine-induced degeneration of the nigrostriatal dopamine pathway: the turning syndrome, PharmacoL Ther. B. 2, 37.
309
Elsevier EIP 20083 Short commnnle_~don
LSD: permanent beha or d effect in rats Peter B. Silverman Department of Psychiatry and Behavioral Sciences, Universityof Texas Medical School at Houston, 1300 Moursun~ Houston, TX 77030, U.S.A.
Received10 December1987,accepted 12 January1988
Rats with a unilateral nigrostaiatal lesion produced by infusion of 6-hydro~--~jdopamine(6-OHDA) exhib/ted acute contralateral (apomorphine-like) rotation in response to systemic LSD administration. When re-introduced to the environment in which LSD had been administered weeks earlier, the animals exhibited a 2-3 rain burst of contralateral rotation. This behavior developed over a period of weeks and could be produced by a single LSD treatment. latent, undrugged rotation is similar to that which we previously reported to result from one or more apomorphine treatments. LSD; Dopamine receptor agonists; Rotational behavior
I. Introduction Rats with unilateral lesions of the nigrostriatal system rotate (turn in circles) in response to challenge with dopamine (DA) receptor agonists (Ungerstedt, 1971). Indirect acting DA receptor agonists (e.g. amphetamine, cocaine) induce ipsilateral circling which has been attributed to DA release/reuptake inhibition occurring only in the intact hemisphere. Direct acting DA receptor agonists, e.g. apomorphine, induce contralaterally directed circling, presumably reflecting denervation supersensitivity in the lesioned striatmn. Pieri et al. (1974) demonstrated that the potent hallucinogen, LSD, acts as a direct DA receptor agonist in this animal preparation. We previously reported that lesioned rats administered a single small dose of apomorphine exhibited a striking, persistent change in behavior (Silverman and Ho, 1981). When placed in the environment in which the single apomorphine treatment had been given, the rats burst into intense contralateral rotation. This brief period of rotation was demonstrable throughout the lifetime of the animals. The behavior had some characteristics of 'simple' associative
learning, e.g. stimulus (environmental) specificity, but other characteristics that m acle it seem anything but simple. For example, low doses were more effective than larger doses in inducing the behavior and there was no recency effect (it took 2 weeks from drug treatment to undrugged test for the behavior to be fufiy expressed). The p~h-pose of the work presented here was to determine ff LSD, a compound that is different from apomorphine in many respects, but which shares the acute rotational effect in m'grostriatally lesioned rats (Pieri et al., 1974), resulted in a longterm behavioral effect similar to that of apomorphine.
2. Materials and methods Male Sprague-Dawley rats (Simon:e~, Gilroy, CA) w~ghi~g 180-240 g were anesthegzed with 40 mg/kg pentobarbital and mounted in a stereotaxic device. A lesion was produced by infusion of 4 /tl of saline containing 0.1~; ascorbate and 2 ~tg//zl (base weight) 6-hydroxydopamine (6OHDA) HBr. Stereotaxic coordinates, with incisor
0014-2999/88/$03.50 © 1988 ElsevierScience Publishers B.V.(BiomedicalDivision)
3~0 bar at ~ , were 1.4 L and 4.2 P from bregma, 8 mm ventr~ from the sku]l surface. The 6-OHDA sohltion was administered at 0.33 p l / m i n via syringe pump, 10 pl syringe, PE 10 tubing and 27 gauge Observations of rotational behavior were made in 26 cm ~ t e r d e a r plastic bowls. Complete 360 ° tams made in 3 ndn ob.q:rvation periods immediately prior to, and immediately after, drug injection and at 15 rain intervals thereafter were ~tecL Subsequent ~ t i o n s of undrugged behavior consisted solely of 3 rain observation begi'nning immediately after the animal was placed in the bowl. During the intervals betweea drug tests and undrugged Observations, rats remained undisturbed in their home cages with ad lib food and water throughout. LSD tartrate (NIDA) was administered i.p. in I m l / k g saline. Animals in Group 1 ( n - - 5 ) were utilized to determine the appropriate doses of LSD to be used in future rotation experiments. They were treated with 50 ~g/'~g LSD four times, 100/xg/kg once and 200/~g/lrg twice. All these drug treatmerits were administered between 2 and 4 weeks after the rats were lesioned. They were subsequently placed in the rotation bowls for 3 rain observations with no further drug treatment at intervals up to 24 weeks after lesion. Group 2 animals (n----4) were treated with 100 ~&/kg LSD once at 4 weeks and again at 6 weeks after being lesioned. Undrugged observations were then made up to 20 weeks after lesion. Group 3 animals ( n - 5) were treated with a sing]e dose of 200 p g / k g LSD at 2 weeks post-lesion. They were observed undrugged at 4 and 8 weeks post-lesion.
3. Rese]ts The ~ t s , summarized in table 1, show that aU groups of animals exhibited, on the average, a sl/ght ips/l~teral bias prior to any drug treatment. Group i animals, which got 50 to 200 ~tg/kg LSD on several occasions, all showed contralateral rotat/on m r - ~ .nse to one or more of the LSD doses. When reintroduced to the rotation environment weeks or months after the last drug treat-
TABLE 1 Undrugged rotational response (X+ S.E.M. contralateral turns/3 rain) upon exposure to the rotation environment prior to, and at various times after, LSD treatment. Negativescores indicate net ipsilateral turns. Group (n) 1(5)
2(4)
Undrusgedresponse Treatment (weeks post-lesion) (weekspost-lesion) -5.0+ 0.4 (2) a 50-2001tg/kgLSD(2-4) 15.6+ 9.1 (6) 44.0-1-12.8 (8) 46.0+ 7.1 (13) 29.8+ 7.2(18) 26.4+ 7.1(24) -1.0+ 0.8 (4) a 0.5 + 0.3 (6)" 4.8+ 8.5± 23.8+
2.9 (8) 6.8(11)
7.8(15) 20.55: 9.5(20) 3(5)
-2.8+ 0.4 (2)" 15.4+ 2.4 (4) 23.6:1:7.0 (8)
1001tg/kgLSD(4) 100 pg/kg LSD (6) -
200/tg/kgLSD(2) -
a Undrugged tests which were followedby the indicated treatmeat(s).
merit, these animals exhibited rapid contralateral rotation. The peak of undrugged rotation was observed at 13 weeks after lesion (9 weeks after the last drug treatment), and a clear response was still apparent 24 weeks post-lesion (20 weeks post-drug). Group 2 animals showed peak acute responses to their two treatments with 100 # g / k g LSD of 25.5 + 10.4 and 39.2 d: 10.8 ~ + S.E.M. turns/3 rain), respectively. In both cases the peak rates were observed in the bin from 15-18 min after injection. Rotation had essentially stopped by the 45-48 rain bin. They showed a shift in the direction of undrugged bias 2 weeks after the first 100 /~g/kg LSD treatment, but not the high speed latent rotational behavior. This behavior did appear after the second drug treatment and became more pronounced with the passage of time. Animals in Group 3, given a single t r e a t m e n t with 200 t t g / k g LSD, exhibited acute contralateral rotation averaging 38.4_-k 4.5 turns/3 rain with the peak rate again observed in the bin beginning 15 rain after injection. Rotation lasted
311
about 45 rain. When placed, undrugged, in the rotation bowls weeks later, they exhibited the rapid contrallateral rotation. One animal from this group died prior to an observation made 20 weeks after the lesion (18 weeks after drug treatment); the other four all still exhibited the behavior.
4. Discussion Ungerstedt (1971; 1976) described an unusual behavior in rats that had been nigrostriatally lesioned with 6-OHDA. Some time after being lesioned, the undrugged animals would show 'explosive' contralateral rotation at the beginning of experimental sessions. Ungerstedt termed this strange behavior 'paradoxical' rotation. We subsequently demonstrated (Si!verman and Ho, 1981) that paradoxical rotation was not a consequence of lesion alone, but the result of prior drug treatment. Lesioned but drug naive animals never demonstrated the behavior, but those that had received even a single apomorphine treatment did so months after the treatment (we tested up to one year after treatment). Rats that had been treated several times with apomorphine displayed marked contralateral rotation and, in many instances, full blown stereotypy when reintroduced to the drug environment. Recently Burunat et al. (1987) have replicated some of our findings using multiple apomorphine administrations. EmphasiTing the role of learning, they pointed out that the rate of rotation in the first minute after the last treatment with apomorphine correlated highly with subsequent undrugged rotation. This relationship does not hold true for the single treatment situation in the case of either apomorphine or LSD. In the first minute after treatment with either of these compounds for the first (and only) time, the animals rotate, if at all, one or two times ipsilaterally. In the single dose case, there does seem to be a positive correlation betweea the peak rate acutely after drug and subsequent undrugged rotation (unpublished observation). The undrugged rotation in some cases exceeds that ever observed while the animal is drugged. Further, in the case of apomorphine this relationship holds only when animals treated with the same single dose are
compared. Larger doses of apomorphine resulted in the same peak rate (but for a period of time) resulted in less subsequent undrugged rotation. One of the remarkable features of latent rotation after a single apomorphine treatment was that the behavior showed no recency effect; it became more robust with the passage of time to 2 weeks after drug treatment, by which time the maximum effect had been reached (Silverman and Ho, 1981). Although not examined as systematically, there appears to be a similar, perhaps longer, 'incubation periods' for LSD-induced latent rotation. Apomorphine-induced latent rotation also showed a peculiar dose response effect in that 50 /tg/kg was a more efficacious dose than 0.25 or 1.0 mg/kg. With LSD, on the other hand, latent rotation was observed 2 weeks after a single dose of 200/tg/kg but not 2 weeks after 100 ~g/kg. Perhaps a single 100/tg/kg dose would have been effective after a longer waiting period. The data presented here show that LSD as well as apomorphine induces a permanent behavioral effect after a single treatment. There is a great deal of current interest in the phenomenon of drug sensitization, i.e. increased response to repeated drug administrations. The undrugged rotational response to apomorphine and LSD would seem to represent the ultimate in context-dependent ~%~!sitization in that it develops after a single dose and is demonstrable without subsequent drug administration.
References Burunat, E., M.D. Diaz-Palarea, R. Castro and M. Rodriguez, 1987, Undmgged rotational response in nigro-striatal system-lesioned rats is related to the previous early response to apomorphine when repeatedly administered, Life St,i. 41, 309. Pieri, L., L. Pieri and W. Haefely, 1974, LSD as an agonist of dopamine receptors in the striatum, Nature 252, 586. Silverman, P.B. and B.T. Ho, 1981, Persistent behavioral effect of apomorphine in 6-hydroxydomaine-lesioned rats, Nature 294, 475. Ungerstedt, U., 1971, Striatal dopamine release after amphetamine or nerve degeneration revealed by rotational behavior, Acta Physiol. Scand. (SuppL) 367, 49. Ungerstedt, U., 1976, 6-Hydroxydopamine-induced degeneration of the nigrostriatal dopamine pathway: the turning syndrome, PharmacoL Ther. B. 2, 37.