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Effect of chronic treatment with neuroleptics on the content of 3′, 5′-cyclic guanosine monophosphate in cerebellar cortex of rats
Life Sciences, Vol . 23, pp . 649-652 Printed in the U .S .A .
Pergamon Press
EFFECT OF CHRONIC TREATMENT WITH NEUROLEPTICS ON THE CONTENT OF 3',5'-CYCLIC GUANOSINE MONOPHOSPHATE IN CEREBELLAR CORTEX OF RATS . G . Biggio, M .G . Corda, M . Casu and G .L . Gessa Institute of Pharmacology, University of Cagliari (Italy) .
Summary Chronic treatment with haloperidol is associated with complete tolerance to the decreasing effect of the neuroleptic on cerebellar cGMP content, vice versa chronic haloperidol cau ses hypersensitivity to the enhancing effect of apona rphine on cerebellar cGMP . Thus, the administration of 0 .5 mg/Kg of haloperidol decreases cerebellar cGMP by 80% in control rats but f_a ils to alter this nucleotide in rats chronically treated with haloperidol (0 .5 m9/Kg twice daily for 20 days) . A dose of 0 .5 mg/Kg of apomorphine enhances cGMP by approximately 25 and 60 percent in control rats and in rats chronically treated with h_a loperidol, respectively . The results suggest that : a) There is a functional link between striatum and cerebellum ; b) Cerebellar cGMP is a sensitive index of the state of activation of str_i atal dopamine receptors . Recently it has been shown that the blockade of dopamine receptors in striatum induced by acute treatment with antipsychotic agents or their destruction by intrastriatal administration of kainic acid produces a marked de crease in the content of 3',5'-cyclic guanosine monophosphate (cGMP) in the c_e rebellar cortex of rats (1, 2, 3) . On the contrary, the systemic or the intras triatal administration of apomorphine, a dopamine mimetic agent, increases cerebellar cGMP (1, 2) . Since cerebellar cGMP content is considered a good biochemical marker of the climbing and parallel fibers function as well as of the functional activity of neurons in the cerebellar cortex (2, 4, 5), the changes of cerebellar cGMP elicited by such treatments indicate that dopamine receptors in striatum are involved in the regulation of cerebellar function . Conve_r sely by measuring the content of cGMP in cerebellar cortex is possible to obtain information of the state of activation of dopamine receptors in the basal ganglia . Chronic treatment with antipsychotics produces changes in striatal dopaminergic activity different from those observed after single injection of these drugs . In fact tolerance develops to their stimulating effect on dopami ne turnover (6), while hypersensitivity is present to various responses of dopamine mimetic agents (7) . To further verify whether the content of cGMP in cerebellar cortex really reflects the dopaminergic transmission in the striatum, we compared the 0300-9653/78/0814-0649$02 .00/0 Copyright (c) 1978 Pergamon Press
650
Chronic Neuroleptica Cerebellar cGMP
Vol . 23, No . 6,
1978
effect of haloperidol and apomorphine in cerebellar cGMP content in control rats and in rats chronically treated with haloperidol . The results show that the changes in the content of cGMP in cerebellar cortex reflect both the state of tolerance to haloperidol and the hypersensitivity of striatal dopamine receptors to dopamine receptor stimulants . Materials and Methods Male Sprague Dawley rats (Charles River, Como, Italy), weighing 150 170 g . the first day of the chronic treatment, were housed in our animal quarters, which were illuminated for 12 hrs a day and maintained at 23-24°C . Two groups of 70 rats each were injected intraperitoneally respectively with saline and haloperidol (Serenase, Janssen), 0 .5 mg/Kg twice daily for 20 days . The acute administration of apomorphine (0 .5 mg/Kg s .c .) and haloper_i dol (0 .5 mg/Kg i .p .) was given 48 hrs after the last of the chronic injections . Rats were killed with a focussed microwave beam (4) punches of cerebellar cor tex were obtained from the brain slices with a 22 gauge stainless needle and cGMP extracted from these samples with perchloric acid, purified on alumina and Dowex columns (4), and assayed using the activation of cGMP-dependent protein kinase (4) . Protein was measured according to Lowry et al . (8) . Results Fig . 1 shows the cGMP content in the cerebellar cortex of rats which were treated twice daily for 20 days with 0 .5 mg/Kg of haloperidol or with sal_i ne and had received the last injection 48 hours before the experiments . to
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n O E
a
E d d
6
0
Fig . 1
Effect of chronic treatment with haloperidol on cGMP content in cerebe_1 lar cortex . * P<0 .01 with respect to saline-treated rats . Rats were killed 30 min after the acute injection of haloperidol (0 .5 mg/Kg i .p .) . Each value is the mean + S .E . of four experiments .
Vol . 23, No . 6, 1978
Chronic Neuroleptice Cerebellar cGMP
651
The content of cGMP in cerebellar cortex of rats chronically treated with haloperidol was not different from that of saline-treated rats . Fourtyeight hours after last treatment the injection of 0 .5 mg/Kg of haloperidol decreased cerebellar cGMP content by 80 percent in saline-treated rats but failed to change the content of this nucleotide in animals chronically treated with haloperidol . In contrast to the tolerance developed toward the effect of haloperidol, chronic treatment caused hypersensitivity to the enhancing effect of apomorphine on cerebellar cGMP content . In fact, as reported in Fig . 2, a dose of 0 .5 mg/Kg of apomorphine increased cerebellar cGMP by approximately 25 and 60 percent in control rats and in rats chronically treated with haloperidol, respectively . ~a
13
L ~" O
s
10
E
w" 0
E a a
5
C1 u
O
Fig . 2 Effect of apomorphine on cGMP content in cerebellar cortex of rats chr_o nically treated with haloperidol . P< 0 .01 with respect to saline-treated rats . P< 0 .01 with respect to rats chronically treated with haloperidol . Rats were killed 12 min after apomorphine (0 .5 mg/Kg s .c .) . Each value is the mean + S . E . of four experiments . Discussion The evidence presented indicates that chronic treatment with antipsychotic agents is associated with tolerance to their decreasing effect on cerebellar cGMP content and with a greater sensitivity toward the enhancing effect of apomorphine on this nucleotide . The loss of effectiveness of haloperidol and the supersensitivity to apomorphine might reflect the phenomena of tolerance and hypersensitivity elicited by chronic treatment at the level of dopamine receptors in the striatum (6, 7) . This hypothesis is supported by previous evide_n ce showing that the intrastriatal injection of haloperidol decreases while apomorphine increases cGMP in cerebellar cortex (1, 2) and by a more recent finding that the destruction of striatal dopamine receptors induced by the local administration of kainic acid produces an almost complete disappearance of this nucleotide in the cerebellar cortex (3) . Thus, as a result of these experiments
652
Chronic Neuroleptica Cerebellar cGMP
Vol . 23, No . 6, 1978
we can consider the content of cGMP in cerebellar cortex a sensitive index of the state of activation of dopamine receptors in striatum . Previous results (1, 2, 3, 5, 9) indicate that a multisynaptic inhibitory pathway connects striatum with the inferior olive ând/or pontine nuclei were the climbing and mossy fibers originate, respectively and that the role of striatal dopamine may be that of swiching-off such pathway, which seems to be the most important, if not the only, neuronal system deactivating cerebellar guanylate cyclase activity . Since striatum and cerebellum are two main brain areas involved in the regulation of motor function and in the coordination of movements the functional link between these two areas suggests that changes in cerebellar function may partecipate in the extrapyramidal disturbances and motor changes produced by neuroleptic drugs .
Italy .
This study was sponsored by grant from Tecnofarmaci S .p .A ., Pomezia, References
1) G . Biggio and A . Guidotti, Nature _265, 240-242 (1977) . 2) G . Biggio, E . Costa and A . Guidotti, J . Pharmacol . Exp . Ther . _200, 207-215 (1977) . 3) G . Biggio, M .G . Corda, M . Casu and G .L . Gessa, Naunyn-Schmiedeberg's Arch . Pharmacol . (in press, 1978) . 4) G . Biggio and A . Guidotti, Brain Res . _107, 365-373 (1976) . 5) G . Biggio, B .B . Brodie, E . Costa and A . Guidotti, Proc . Nat . Acad . Sci . _74, 3592-3596 (1977) . 6) P . Lerner, P . Nose, E . K . Gordon and W . Lovenberg, Science _197, 181-183
(1977) . 7) I . Creese and S .D . Iversen, Brain Res . _83, 419-426 (1975) . 8) O . H . Lowry, N .S . Roserbrough, A .L . Farr and R .S . Randall, J . Biol . Chem . _193, 265-275 (1951) . 9) G . Biggio, M .G . Corda, M . Casu and G .L . Gessa, in Adv . Biochem . Psychophar macol . vol . 18, pp . 227-244, Raven Press, New York (1978) .
Pergamon Press
EFFECT OF CHRONIC TREATMENT WITH NEUROLEPTICS ON THE CONTENT OF 3',5'-CYCLIC GUANOSINE MONOPHOSPHATE IN CEREBELLAR CORTEX OF RATS . G . Biggio, M .G . Corda, M . Casu and G .L . Gessa Institute of Pharmacology, University of Cagliari (Italy) .
Summary Chronic treatment with haloperidol is associated with complete tolerance to the decreasing effect of the neuroleptic on cerebellar cGMP content, vice versa chronic haloperidol cau ses hypersensitivity to the enhancing effect of apona rphine on cerebellar cGMP . Thus, the administration of 0 .5 mg/Kg of haloperidol decreases cerebellar cGMP by 80% in control rats but f_a ils to alter this nucleotide in rats chronically treated with haloperidol (0 .5 m9/Kg twice daily for 20 days) . A dose of 0 .5 mg/Kg of apomorphine enhances cGMP by approximately 25 and 60 percent in control rats and in rats chronically treated with h_a loperidol, respectively . The results suggest that : a) There is a functional link between striatum and cerebellum ; b) Cerebellar cGMP is a sensitive index of the state of activation of str_i atal dopamine receptors . Recently it has been shown that the blockade of dopamine receptors in striatum induced by acute treatment with antipsychotic agents or their destruction by intrastriatal administration of kainic acid produces a marked de crease in the content of 3',5'-cyclic guanosine monophosphate (cGMP) in the c_e rebellar cortex of rats (1, 2, 3) . On the contrary, the systemic or the intras triatal administration of apomorphine, a dopamine mimetic agent, increases cerebellar cGMP (1, 2) . Since cerebellar cGMP content is considered a good biochemical marker of the climbing and parallel fibers function as well as of the functional activity of neurons in the cerebellar cortex (2, 4, 5), the changes of cerebellar cGMP elicited by such treatments indicate that dopamine receptors in striatum are involved in the regulation of cerebellar function . Conve_r sely by measuring the content of cGMP in cerebellar cortex is possible to obtain information of the state of activation of dopamine receptors in the basal ganglia . Chronic treatment with antipsychotics produces changes in striatal dopaminergic activity different from those observed after single injection of these drugs . In fact tolerance develops to their stimulating effect on dopami ne turnover (6), while hypersensitivity is present to various responses of dopamine mimetic agents (7) . To further verify whether the content of cGMP in cerebellar cortex really reflects the dopaminergic transmission in the striatum, we compared the 0300-9653/78/0814-0649$02 .00/0 Copyright (c) 1978 Pergamon Press
650
Chronic Neuroleptica Cerebellar cGMP
Vol . 23, No . 6,
1978
effect of haloperidol and apomorphine in cerebellar cGMP content in control rats and in rats chronically treated with haloperidol . The results show that the changes in the content of cGMP in cerebellar cortex reflect both the state of tolerance to haloperidol and the hypersensitivity of striatal dopamine receptors to dopamine receptor stimulants . Materials and Methods Male Sprague Dawley rats (Charles River, Como, Italy), weighing 150 170 g . the first day of the chronic treatment, were housed in our animal quarters, which were illuminated for 12 hrs a day and maintained at 23-24°C . Two groups of 70 rats each were injected intraperitoneally respectively with saline and haloperidol (Serenase, Janssen), 0 .5 mg/Kg twice daily for 20 days . The acute administration of apomorphine (0 .5 mg/Kg s .c .) and haloper_i dol (0 .5 mg/Kg i .p .) was given 48 hrs after the last of the chronic injections . Rats were killed with a focussed microwave beam (4) punches of cerebellar cor tex were obtained from the brain slices with a 22 gauge stainless needle and cGMP extracted from these samples with perchloric acid, purified on alumina and Dowex columns (4), and assayed using the activation of cGMP-dependent protein kinase (4) . Protein was measured according to Lowry et al . (8) . Results Fig . 1 shows the cGMP content in the cerebellar cortex of rats which were treated twice daily for 20 days with 0 .5 mg/Kg of haloperidol or with sal_i ne and had received the last injection 48 hours before the experiments . to
c ô
n O E
a
E d d
6
0
Fig . 1
Effect of chronic treatment with haloperidol on cGMP content in cerebe_1 lar cortex . * P<0 .01 with respect to saline-treated rats . Rats were killed 30 min after the acute injection of haloperidol (0 .5 mg/Kg i .p .) . Each value is the mean + S .E . of four experiments .
Vol . 23, No . 6, 1978
Chronic Neuroleptice Cerebellar cGMP
651
The content of cGMP in cerebellar cortex of rats chronically treated with haloperidol was not different from that of saline-treated rats . Fourtyeight hours after last treatment the injection of 0 .5 mg/Kg of haloperidol decreased cerebellar cGMP content by 80 percent in saline-treated rats but failed to change the content of this nucleotide in animals chronically treated with haloperidol . In contrast to the tolerance developed toward the effect of haloperidol, chronic treatment caused hypersensitivity to the enhancing effect of apomorphine on cerebellar cGMP content . In fact, as reported in Fig . 2, a dose of 0 .5 mg/Kg of apomorphine increased cerebellar cGMP by approximately 25 and 60 percent in control rats and in rats chronically treated with haloperidol, respectively . ~a
13
L ~" O
s
10
E
w" 0
E a a
5
C1 u
O
Fig . 2 Effect of apomorphine on cGMP content in cerebellar cortex of rats chr_o nically treated with haloperidol . P< 0 .01 with respect to saline-treated rats . P< 0 .01 with respect to rats chronically treated with haloperidol . Rats were killed 12 min after apomorphine (0 .5 mg/Kg s .c .) . Each value is the mean + S . E . of four experiments . Discussion The evidence presented indicates that chronic treatment with antipsychotic agents is associated with tolerance to their decreasing effect on cerebellar cGMP content and with a greater sensitivity toward the enhancing effect of apomorphine on this nucleotide . The loss of effectiveness of haloperidol and the supersensitivity to apomorphine might reflect the phenomena of tolerance and hypersensitivity elicited by chronic treatment at the level of dopamine receptors in the striatum (6, 7) . This hypothesis is supported by previous evide_n ce showing that the intrastriatal injection of haloperidol decreases while apomorphine increases cGMP in cerebellar cortex (1, 2) and by a more recent finding that the destruction of striatal dopamine receptors induced by the local administration of kainic acid produces an almost complete disappearance of this nucleotide in the cerebellar cortex (3) . Thus, as a result of these experiments
652
Chronic Neuroleptica Cerebellar cGMP
Vol . 23, No . 6, 1978
we can consider the content of cGMP in cerebellar cortex a sensitive index of the state of activation of dopamine receptors in striatum . Previous results (1, 2, 3, 5, 9) indicate that a multisynaptic inhibitory pathway connects striatum with the inferior olive ând/or pontine nuclei were the climbing and mossy fibers originate, respectively and that the role of striatal dopamine may be that of swiching-off such pathway, which seems to be the most important, if not the only, neuronal system deactivating cerebellar guanylate cyclase activity . Since striatum and cerebellum are two main brain areas involved in the regulation of motor function and in the coordination of movements the functional link between these two areas suggests that changes in cerebellar function may partecipate in the extrapyramidal disturbances and motor changes produced by neuroleptic drugs .
Italy .
This study was sponsored by grant from Tecnofarmaci S .p .A ., Pomezia, References
1) G . Biggio and A . Guidotti, Nature _265, 240-242 (1977) . 2) G . Biggio, E . Costa and A . Guidotti, J . Pharmacol . Exp . Ther . _200, 207-215 (1977) . 3) G . Biggio, M .G . Corda, M . Casu and G .L . Gessa, Naunyn-Schmiedeberg's Arch . Pharmacol . (in press, 1978) . 4) G . Biggio and A . Guidotti, Brain Res . _107, 365-373 (1976) . 5) G . Biggio, B .B . Brodie, E . Costa and A . Guidotti, Proc . Nat . Acad . Sci . _74, 3592-3596 (1977) . 6) P . Lerner, P . Nose, E . K . Gordon and W . Lovenberg, Science _197, 181-183
(1977) . 7) I . Creese and S .D . Iversen, Brain Res . _83, 419-426 (1975) . 8) O . H . Lowry, N .S . Roserbrough, A .L . Farr and R .S . Randall, J . Biol . Chem . _193, 265-275 (1951) . 9) G . Biggio, M .G . Corda, M . Casu and G .L . Gessa, in Adv . Biochem . Psychophar macol . vol . 18, pp . 227-244, Raven Press, New York (1978) .