Effects of p-chlorophenylalanine on striatal acetylcholinesterase activityand on biogenic amine levels in nuclei raphe and caudate-putamen during physostigmine-induced tremor in rats

The biochemical mechanism underlying tremor is unknown. We investigated the effects of p-chlorophenylalanine (pCPA), a serotonin (5-HT) depletor, on t he neurochemical processes in nuclei raphe dorsalis (NRD) and caudatus puta men (NCP) paralleling physostigmine-induced tremor in rats. Peak of physost igmine tremor correlated with increase in 5-HT in NRD and NCP, and a decrea se in striatal dopamine (DA), as assayed employing high pressure liquid chr omotography-electrochemistry. Administration of pCPA caused significant dec rease in DA, norepinephrine (NE) and 5-HT levels in both the nuclei, withou t affecting striatal NE content and acetylcholinesterase activity. pCPA pre treatment significantly inhibited physostigmine-induced tremor and blocked corresponding increase in the levels of 5-HT in NRD and NCP. These results indicate involvement of central 5-MT, but not DA or NE, in the genesis of p hysostigmine tremor. (C) 2001 Elsevier Science Ireland Ltd. All rights rese rved.