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Time course of apomorphine-induced circling behaviour after striatal dopamine receptor denervation
European Journal of Pharmacology, 62 (1980) 107--110
107
© Elsevier/North-Holland Biomedical Press
Short communication TIME COURSE OF APOMORPHINE-INDUCED CIRCLING BEHAVIOUR AFTER STRIATAL DOPAMINE RECEPTOR DENERVATION CLAUDE OBERLANDER, CLAUDE DUMONT and JACQUES R. BOISSIER
Centre de Recherches Roussel-Uclaf, 93230 Romainville, France Received 7 January 1980, accepted 8 January 1980
C. OBERLANDER, C. DUMONT and J.R. BOISSIER, Time course of apomorphine-induced circling behaviour after striatal dopamine receptor denervation, European J. Pharmacol. 62 (1980) 107--110. The curve describing the time course of apomorphine-induced circling behaviour in rats with a 6-hydroxydopamine-induced lesion of the nigrostriatal dopamine (DA) pathway was studied with a microcompnterized rotometer. Up to a 2-week interval after lesioning, the contralateral circling response was a single bell-shaped curve but this gradually became a double-peaked curve after 4-5 months. At this time the bell-shaped curve was, however, restored by haloperidol pretreatment. It is concluded that the response of striatal DA receptors was modified either by the lesion of another neuronal system and/or that the absence of DA nerve endings induced changes in the striatal DA receptor itself. Denervated DA receptor
Apomorphine
Striatum
I. Introduction The rotational model using lesioned rats allows an objective and automated quantification of central dopamine (DA) receptor stimulating properties. When the nigrostriatal DA pathway is unilaterally lesioned by 6-hydroxydopamine (6-OHDA) injection, the lesioned side becomes hypersensitive to DA receptor agonists as compared with the intact side (Ungerstedt, 1971) and contralateral rotations induced by DA receptor agonists are an index of the reactivity of the denervated striatal DA receptors. In animals with a disruption of one striatum or of one striatonigral t r a c t - - a pathway necessary for the expression of rotations (Marshall and Ungerstedt, 1 9 7 7 ) - DA agonists induce ipsilateral turns, which indicates an action on the remaining unlesioned nigrostriatal DA pathway. Both models were used for the sequential recording of rotations with a computerized
Rotometer
Circling behaviour
system. This revealed marked changes in the time-curve to the DA receptor agonist apomorphine following deafferentiation of striatal DA receptors when compared with innervated receptors.
2. Materi~l.q and methods
Male Sprague Dawley rats weighing 225 + 15 g at the time of surgery were unilaterally lesioned by one of two methods. Either 6~)HDA hydrochloride (8/~g as the free base in 4/zl of artificial CSF containing 1 mg/ml of ascorbic acid at a 1 #l/min rate) was injected into the right medial forebrain bundle (MFB) according to the coordinates A: 4.0; H: 2.8; L: 1.0 of KSnig and Klippel (1963), or an anodal current of 60 mC was passed through a steel electrode (section 0.45 m m , tip 0.45 mm) centered in the substantia nigra pars reticulata (SNr) at the coordinates A: 2.7; H: 2.2; L: 2.0. Apomorphine hydro-
108
C. OBERLANDER ET AL.
chloride was diluted in water and given as a subcutaneous (s.c.) injection in the flank, whilst haloperidol was dissolved in a 0.25 mg/ml tartaric acid solution and injected intraperitoneaUy (i.p.). Each rat was introduced into one compartment o f an eightcompartment r o t o m e t e r connected to a microcomputer with independent electronic clocks on each channel. Ipsilateral and contralateral turns were recorded as positive and negative values respectively accumulated in 5 min periods. Time course curves expressed in turns/min with the standard error were obtained off-line on a central computer.
shown in fig. 1, the last response curve induced by apomorphine was bell-shaped, the maximal amplitude being observed around 20 min after injection (fig. 1). A 0.1 mg/kg dose of apomorphine was, however, ineffective. In 6~)HDA-lesioned rats (fig. 1), the test dose of apomorphine was reduced to 0.05 mg/kg in order to take into account the developing denervation supersensitivity. One week post-lesion the shape of the response curve was sharper b u t similar to that of SNr lesioned rats, except for the direction o f rotations. However, 5-8 weeks after lesioning, the time-response profile was highly modified. This was characterized by a shortlatency response, with its maximum at about 10 min, which was followed b y a decrease then an increase in the rate of rotations, the latter being maximal at 40 min. A continuous evolution between the single and the doublepeaked curve was observed in the intermediate period. After 8 months, the distinction between the early and late responses was still more pronounced. In such rats, a lower dose
3. Results Except for a spontaneous and transient period of contralateral m o t o r asymmetry, a 0.5 mg/kg dose of apomorphine consistently elicited ipsilateral rotations with the same order of potency, when tested at 2, 4, 10 or 15 weeks, 6 or 10 months after lesion. As
ELECTROLYTIC SNr LESION
6-OHDA MFB LESION v
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TIME(MIN)
Fig. 1. Circling behaviour induced at various time intervals after lesioning, by apomorphine 0.05 mg/kg (6-OHDA MFB lesion) or 0.5 mg/kg (10 months after electrolytic lesion of the SNr). Lower right diagram shows the effect of haloperidol pretreatment (0.5 mg/kg, 30 min before test; dashed line) compared with the control test in the same animals. *P = 0.05; **P = 0.01 by Student's t-test for paired groups. Positive values: ipsilateral turns; negative values: contralateral turns, n = 8-14 rats per group.
TIME COURSE OF APOMORPHINE-INDUCEDCIRCLING of apomorphine (0.02 mg/kg) had a similar effect while a higher dose (0.2mg/kg) induced the short latency response followed by a plateau. Two peaked curves were also obtained after the i.p. injection of apomorphine. In some cases the evolution of the response curve did not differ from that of other rats, up to 5 weeks after lesioning. After this no further change was observed. After pretreatment with the DA receptor blocker haloperidol (fig. 1) the double-peaked response was converted into a single-peaked response, similar to that observed in SNr lesioned rats or a short time after the 6-OHDA-induced lesion. Low doses of haloperidol mainly increased the latency of onset, and decreased the duration of rotations.
4. Discussion
Early spontaneous contralateral rotations sometimes occur in 6~3HDA4esioned rats when t h e y are merely handled; these rotations have been attributed to stress (Ungerstedt, 1971). Nevertheless, we found that the first peak of apomorphine action was consistently elicited in rats adapted to the experimental conditions by chronic treatment. Furthermore, in saline-treated animals, the intensity and duration of these rotations were far less marked and the rotations themselves occurred earlier than the short-latency response induced by apomorphine. However, interaction between these two processes cannot be excluded and the first response may trigger off a transient inhibition of a further action of the DA agonist. The double effect of apomorphine is not consistent with either two different modalities for its resorption or the occurrence of a pharmacologically active metabolite. This is suggested by the similarity of the effects observed after s.c. or i.p. administration, and the occurrence of a similar profile with L-DOPA (results not shown). The particular response elicited in denervated striatal DA receptors could be linked with the 6~)HDA-induced deafferentiation of other
109
monoaminergic systems modulating the action o f the striatal system. The mesolimbic DA system, for example, was shown to interfere with the nigrostriatal DA system in the rotating model (Kelly and Moore, 1976). The ventral noradrenergic bundle, in contrast to serotonergic fibres (Pieri et al., 1975), was also affected by the 6~)HDA lesion. It is worth noting that differences have recently been described in the kinetics of apomorphineinduced rotations of animals lesioned with 6-OHDA or with 5,6-hydroxytryptamine, an agent which furthermore destroys serotonergic neurons (Waddington and Crow, 1978). However, we nave observed no difference between 6-OHDA and 5,6 HT-lesioned rats (unpublished results). There are data showing that denervated striatal DA receptors partly lose their specificity for the neurotransmitter (Costall et al., 1976), while denervation leads to supersensitivity through a possible increase in the number of DA receptors (Creese et al., 1977). Therefore, our curves could reveal the existence of different types of DA receptor, these being either induced or modified by denervation. This view is supported by the progressive onset o f the double-peaked curve. Whatever the mechanism of the phenomenon, the marked modification o f the response curve before and after haloperidol treatment emphasizes the discrepancies which may result from the m e t h o d used to estimate the action of a DA blocker. Paradoxically, 25 min after apomorphine injection, there was a significant increase in rotations in the haloperidol interaction experiments (see fig. 1). Furthermore, it is obvious that important qualitative as well as quantitative changes occur during the time period when 6-OHDAlesioned rats are generally used for behavioral tests. Finally, detailed study of the time-response relations of dopaminergic drugs in 6~3HDAlesioned rats could offer a new means of investigating the m o d e of action of these drugs.
110
Acknowledgements We wish to thank Yanick Demassey and Annick Verdu for their technical assistance.
References Costall, B., R.J. Naylor and C. Pycock, 1976, Non specific supersensitivity of striatal dopamine receptors after 6-hydroxydopamine lesion of the nigrostriatal pathway, European J. Pharmacol. 35, 275. Creese, I., D.R. Butt and S.H. Snyder, 1977, Dopamine receptor binding enhancement accompanies lesion-induced behavioral supersensitivity, Science 197,596. Kelly, P.H. and K.E. Moore, 1976, Mcsolimbic dopaminergic neurons in the rotational model of nigrostriatal function, Nature (London) 263, 695.
C. OBERLANDER ET AL. K•nig, J.F.R. and R.A. Klippel, 1963, in: The Rat Brain: a Stereotaxic Atlas of the Forebrain and Lower Parts of the Brain Stem (Williams and Williams, Baltimore, USA). Marshall, J.F. and U. Ungerstedt, 1977, Striatal efferent fibers play a role in maintaining rotational behaviour in the rat, Science 198, 62. Pieri, M., L. Pied, A. Saner, M. Da Prada and W. Haefely, 1975, A comparison of drug-induced rotation in rats lesioned in the medial forebrain bundle with 5,6-dihydroxytryptamine or 6hydroxydopamine, Arch. Int. Pharmacodyn. Ther. 217, 118. Ungerstedt, U., 1971, Striatal dopamine release after amphetamine or nerve degeneration revealed by rotational behaviour, Acta Physiol. Scand. 82, Suppl. 367, 49. Waddington, J.S. and T.J. Crow, 1978, Methodological problems in the measurement of drug-induced rotational behaviour: continuous recording reveals time-course differences undetected by previous techniques, Psychopharmacology 58,153.
107
© Elsevier/North-Holland Biomedical Press
Short communication TIME COURSE OF APOMORPHINE-INDUCED CIRCLING BEHAVIOUR AFTER STRIATAL DOPAMINE RECEPTOR DENERVATION CLAUDE OBERLANDER, CLAUDE DUMONT and JACQUES R. BOISSIER
Centre de Recherches Roussel-Uclaf, 93230 Romainville, France Received 7 January 1980, accepted 8 January 1980
C. OBERLANDER, C. DUMONT and J.R. BOISSIER, Time course of apomorphine-induced circling behaviour after striatal dopamine receptor denervation, European J. Pharmacol. 62 (1980) 107--110. The curve describing the time course of apomorphine-induced circling behaviour in rats with a 6-hydroxydopamine-induced lesion of the nigrostriatal dopamine (DA) pathway was studied with a microcompnterized rotometer. Up to a 2-week interval after lesioning, the contralateral circling response was a single bell-shaped curve but this gradually became a double-peaked curve after 4-5 months. At this time the bell-shaped curve was, however, restored by haloperidol pretreatment. It is concluded that the response of striatal DA receptors was modified either by the lesion of another neuronal system and/or that the absence of DA nerve endings induced changes in the striatal DA receptor itself. Denervated DA receptor
Apomorphine
Striatum
I. Introduction The rotational model using lesioned rats allows an objective and automated quantification of central dopamine (DA) receptor stimulating properties. When the nigrostriatal DA pathway is unilaterally lesioned by 6-hydroxydopamine (6-OHDA) injection, the lesioned side becomes hypersensitive to DA receptor agonists as compared with the intact side (Ungerstedt, 1971) and contralateral rotations induced by DA receptor agonists are an index of the reactivity of the denervated striatal DA receptors. In animals with a disruption of one striatum or of one striatonigral t r a c t - - a pathway necessary for the expression of rotations (Marshall and Ungerstedt, 1 9 7 7 ) - DA agonists induce ipsilateral turns, which indicates an action on the remaining unlesioned nigrostriatal DA pathway. Both models were used for the sequential recording of rotations with a computerized
Rotometer
Circling behaviour
system. This revealed marked changes in the time-curve to the DA receptor agonist apomorphine following deafferentiation of striatal DA receptors when compared with innervated receptors.
2. Materi~l.q and methods
Male Sprague Dawley rats weighing 225 + 15 g at the time of surgery were unilaterally lesioned by one of two methods. Either 6~)HDA hydrochloride (8/~g as the free base in 4/zl of artificial CSF containing 1 mg/ml of ascorbic acid at a 1 #l/min rate) was injected into the right medial forebrain bundle (MFB) according to the coordinates A: 4.0; H: 2.8; L: 1.0 of KSnig and Klippel (1963), or an anodal current of 60 mC was passed through a steel electrode (section 0.45 m m , tip 0.45 mm) centered in the substantia nigra pars reticulata (SNr) at the coordinates A: 2.7; H: 2.2; L: 2.0. Apomorphine hydro-
108
C. OBERLANDER ET AL.
chloride was diluted in water and given as a subcutaneous (s.c.) injection in the flank, whilst haloperidol was dissolved in a 0.25 mg/ml tartaric acid solution and injected intraperitoneaUy (i.p.). Each rat was introduced into one compartment o f an eightcompartment r o t o m e t e r connected to a microcomputer with independent electronic clocks on each channel. Ipsilateral and contralateral turns were recorded as positive and negative values respectively accumulated in 5 min periods. Time course curves expressed in turns/min with the standard error were obtained off-line on a central computer.
shown in fig. 1, the last response curve induced by apomorphine was bell-shaped, the maximal amplitude being observed around 20 min after injection (fig. 1). A 0.1 mg/kg dose of apomorphine was, however, ineffective. In 6~)HDA-lesioned rats (fig. 1), the test dose of apomorphine was reduced to 0.05 mg/kg in order to take into account the developing denervation supersensitivity. One week post-lesion the shape of the response curve was sharper b u t similar to that of SNr lesioned rats, except for the direction o f rotations. However, 5-8 weeks after lesioning, the time-response profile was highly modified. This was characterized by a shortlatency response, with its maximum at about 10 min, which was followed b y a decrease then an increase in the rate of rotations, the latter being maximal at 40 min. A continuous evolution between the single and the doublepeaked curve was observed in the intermediate period. After 8 months, the distinction between the early and late responses was still more pronounced. In such rats, a lower dose
3. Results Except for a spontaneous and transient period of contralateral m o t o r asymmetry, a 0.5 mg/kg dose of apomorphine consistently elicited ipsilateral rotations with the same order of potency, when tested at 2, 4, 10 or 15 weeks, 6 or 10 months after lesion. As
ELECTROLYTIC SNr LESION
6-OHDA MFB LESION v
i
4 . ~ ~
-I0.
0
~(
20 40
•
i---,
.--------.
........
,---i
-,-
• ---
i
,
i
---,
. . . . .r . .
,
. . . l. . .
, . . . . .r . .
,---
i
,-
.
.
.
.
.
.
.
.
o ........
, ........
,
. . . . . . . .
, ........
, ....
TIME(MIN)
Fig. 1. Circling behaviour induced at various time intervals after lesioning, by apomorphine 0.05 mg/kg (6-OHDA MFB lesion) or 0.5 mg/kg (10 months after electrolytic lesion of the SNr). Lower right diagram shows the effect of haloperidol pretreatment (0.5 mg/kg, 30 min before test; dashed line) compared with the control test in the same animals. *P = 0.05; **P = 0.01 by Student's t-test for paired groups. Positive values: ipsilateral turns; negative values: contralateral turns, n = 8-14 rats per group.
TIME COURSE OF APOMORPHINE-INDUCEDCIRCLING of apomorphine (0.02 mg/kg) had a similar effect while a higher dose (0.2mg/kg) induced the short latency response followed by a plateau. Two peaked curves were also obtained after the i.p. injection of apomorphine. In some cases the evolution of the response curve did not differ from that of other rats, up to 5 weeks after lesioning. After this no further change was observed. After pretreatment with the DA receptor blocker haloperidol (fig. 1) the double-peaked response was converted into a single-peaked response, similar to that observed in SNr lesioned rats or a short time after the 6-OHDA-induced lesion. Low doses of haloperidol mainly increased the latency of onset, and decreased the duration of rotations.
4. Discussion
Early spontaneous contralateral rotations sometimes occur in 6~3HDA4esioned rats when t h e y are merely handled; these rotations have been attributed to stress (Ungerstedt, 1971). Nevertheless, we found that the first peak of apomorphine action was consistently elicited in rats adapted to the experimental conditions by chronic treatment. Furthermore, in saline-treated animals, the intensity and duration of these rotations were far less marked and the rotations themselves occurred earlier than the short-latency response induced by apomorphine. However, interaction between these two processes cannot be excluded and the first response may trigger off a transient inhibition of a further action of the DA agonist. The double effect of apomorphine is not consistent with either two different modalities for its resorption or the occurrence of a pharmacologically active metabolite. This is suggested by the similarity of the effects observed after s.c. or i.p. administration, and the occurrence of a similar profile with L-DOPA (results not shown). The particular response elicited in denervated striatal DA receptors could be linked with the 6~)HDA-induced deafferentiation of other
109
monoaminergic systems modulating the action o f the striatal system. The mesolimbic DA system, for example, was shown to interfere with the nigrostriatal DA system in the rotating model (Kelly and Moore, 1976). The ventral noradrenergic bundle, in contrast to serotonergic fibres (Pieri et al., 1975), was also affected by the 6~)HDA lesion. It is worth noting that differences have recently been described in the kinetics of apomorphineinduced rotations of animals lesioned with 6-OHDA or with 5,6-hydroxytryptamine, an agent which furthermore destroys serotonergic neurons (Waddington and Crow, 1978). However, we nave observed no difference between 6-OHDA and 5,6 HT-lesioned rats (unpublished results). There are data showing that denervated striatal DA receptors partly lose their specificity for the neurotransmitter (Costall et al., 1976), while denervation leads to supersensitivity through a possible increase in the number of DA receptors (Creese et al., 1977). Therefore, our curves could reveal the existence of different types of DA receptor, these being either induced or modified by denervation. This view is supported by the progressive onset o f the double-peaked curve. Whatever the mechanism of the phenomenon, the marked modification o f the response curve before and after haloperidol treatment emphasizes the discrepancies which may result from the m e t h o d used to estimate the action of a DA blocker. Paradoxically, 25 min after apomorphine injection, there was a significant increase in rotations in the haloperidol interaction experiments (see fig. 1). Furthermore, it is obvious that important qualitative as well as quantitative changes occur during the time period when 6-OHDAlesioned rats are generally used for behavioral tests. Finally, detailed study of the time-response relations of dopaminergic drugs in 6~3HDAlesioned rats could offer a new means of investigating the m o d e of action of these drugs.
110
Acknowledgements We wish to thank Yanick Demassey and Annick Verdu for their technical assistance.
References Costall, B., R.J. Naylor and C. Pycock, 1976, Non specific supersensitivity of striatal dopamine receptors after 6-hydroxydopamine lesion of the nigrostriatal pathway, European J. Pharmacol. 35, 275. Creese, I., D.R. Butt and S.H. Snyder, 1977, Dopamine receptor binding enhancement accompanies lesion-induced behavioral supersensitivity, Science 197,596. Kelly, P.H. and K.E. Moore, 1976, Mcsolimbic dopaminergic neurons in the rotational model of nigrostriatal function, Nature (London) 263, 695.
C. OBERLANDER ET AL. K•nig, J.F.R. and R.A. Klippel, 1963, in: The Rat Brain: a Stereotaxic Atlas of the Forebrain and Lower Parts of the Brain Stem (Williams and Williams, Baltimore, USA). Marshall, J.F. and U. Ungerstedt, 1977, Striatal efferent fibers play a role in maintaining rotational behaviour in the rat, Science 198, 62. Pieri, M., L. Pied, A. Saner, M. Da Prada and W. Haefely, 1975, A comparison of drug-induced rotation in rats lesioned in the medial forebrain bundle with 5,6-dihydroxytryptamine or 6hydroxydopamine, Arch. Int. Pharmacodyn. Ther. 217, 118. Ungerstedt, U., 1971, Striatal dopamine release after amphetamine or nerve degeneration revealed by rotational behaviour, Acta Physiol. Scand. 82, Suppl. 367, 49. Waddington, J.S. and T.J. Crow, 1978, Methodological problems in the measurement of drug-induced rotational behaviour: continuous recording reveals time-course differences undetected by previous techniques, Psychopharmacology 58,153.