Effects of serotoninergic drugs on tremor induced by physostigmine in rats.
We investigated the effects of various serotoninergic drugs and serotonin (5-HT) depletion on physostigmine-induced visible tremor in rats. Physostigmine (0.25-1.5 mg/kg) caused dose-dependent tremor, initiated at 3-5 min (latency decreases as dose increases) and lasted for 30-35 min. Serotonin agonists, 8-hydroxy-2-(di-n-propylamino) tetralin (2.5 mg/kg) and buspirone (5 mg/kg) augmented the tremor response caused by physostigmine. The 5-HT(1)/5-HT(2) receptor antagonist, metergoline (1 mg/kg), and 5-HT(2) blocker, cyproheptadine (10 mg/kg) significantly decreased the duration (40%) as well as intensity (45-50%) of physostigmine-tremor. The 5-HT(2a)/5-HT(2c) antagonist ritanserin (5 mg/kg) significantly reduced the duration (60%) without affecting the intensity of the tremor. In 5-HT depleted rats (p-chlorophenylalanine; 300 mg/kg, for 3 days), physostigmine failed to produce tremor. Interestingly, in these animals, administration of a non-specific 5-HT agonist, 5-methoxy-N,N-dimethyl tryptamine, caused high intensity tremor. These results suggest that presence of 5-HT at the pre-synaptic terminals is needed for the tremor response by physostigmine and the response is greatly mediated via post-synaptic 5-HT receptors. The overall data indicated a direct involvement of central 5-HT system in the cholinergic tremor induced by physostigmine.
Sarkar
S
S
Division of Pharmacology and Experimental Therapeutics, Indian Institute of Chemical Biology, 4, Raja S.C. Mullick Road, Calcutta, India.
Thomas
B
B
Muralikrishnan
D
D
Mohanakumar
K P
KP
D000818:Animals; D002065:Buspirone / Q000494:pharmacology; D002800:Cholinesterase Inhibitors / Q000009:adverse effects*; D003533:Cyproheptadine / Q000494:pharmacology; D008711:Metergoline / Q000494:pharmacology; D004130:N,N-Dimethyltryptamine / Q000494:pharmacology; D010830:Physostigmine / Q000009:adverse effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000187:drug effects / Q000378:metabolism*; D016713:Ritanserin / Q000494:pharmacology; D012701:Serotonin / Q000378:metabolism* / Q000502:physiology; D018490:Serotonin Agents / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D014202:Tremor / Q000139:chemically induced*
D002800:Cholinesterase Inhibitors; D011985:Receptors, Serotonin; D018490:Serotonin Agents; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D013764:Tetrahydronaphthalenes; D016713:Ritanserin; D008711:Metergoline; D003533:Cyproheptadine; D012701:Serotonin; D010830:Physostigmine; C095210:tetralin; D002065:Buspirone; D004130:N,N-Dimethyltryptamine