Interaction of central serotonin and dopamine in the regulation of carbaryl-induced tremor.
Carbaryl (50-200 mg/kg, p.o.) produced dose-dependent tremors and inhibition of striatal AChE activity. A dose-dependent elevation of striatal 5-HT and 5-HIAA levels was also observed with carbaryl but at the higher doses (100-200 mg/kg p.o.). L-Trp or 5-HTP or haloperidol potentiated the carbaryl-induced tremors. Further, 5-HTP or haloperidol, when administered (i) alone, reduced the ED50 value and increased the duration of carbaryl-induced tremors without affecting the maximum tremorogenic response of rats and (ii) together, did not change any of these measures significantly. Atropine (acetylcholine antagonist) completely blocked the tremors produced by carbaryl in the absence or presence of 5-HTP or haloperidol. Methysergide (5-HT antagonist) and bromocriptine (DA agonist) antagonised the potentiating effect of 5-HTP and haloperidol, respectively, on the carbaryl-induced tremors. Furthermore, bromocriptine antagonised the potentiating effect of 5-HTP on the carbaryl-induced tremor but, methysergide failed to achieve this antagonism in presence of haloperidol. These results indicate that carbaryl-induced tremors primarily involve the activation of central cholinoceptors and that the serotonergic potentiation of carbaryl-induced tremors is possibly mediated through the dopaminergic disinhibition of cholinergic neurons.
Department of Biochemistry, University College of Science, University of Calcutta, India.
S K
SK
Ray
M K
MK
Poddar
D006916:5-Hydroxytryptophan / Q000494:pharmacology; D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001522:Behavior, Animal / Q000187:drug effects; D001923:Brain Chemistry / Q000187:drug effects; D001971:Bromocriptine / Q000494:pharmacology; D012721:Carbaryl; D003342:Corpus Striatum / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D004298:Dopamine / Q000502:physiology*; D006220:Haloperidol / Q000494:pharmacology; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D010830:Physostigmine / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000502:physiology*; D014202:Tremor / Q000139:chemically induced / Q000503:physiopathology*
D012701:Serotonin; D001971:Bromocriptine; D006897:Hydroxyindoleacetic Acid; D001285:Atropine; D010830:Physostigmine; D006916:5-Hydroxytryptophan; D000110:Acetylcholinesterase; D006220:Haloperidol; D012721:Carbaryl; D004298:Dopamine; D008784:Methysergide