8-OH DPAT, A 5-HT1A AGONIST AND RITANSERIN, A 5-HT2A C ANTAGONIST, REVERSE HALOPERIDOL-INDUCED CATALEPSY IN RATS INDEPENDENTLY OF STRIATAL DOPAMINE RELEASE/

In this study, both catalepsy and changes in extracellular levels of s triatal dopamine (DA) and dihydroxyphenyl acetic acid (DOPAC) induced by the typical neuroleptic haloperidol (HAL) were simultaneously asses sed, using intracerebral microdialysis in freely moving rats, in the p resence of either the 5-HT1A agonist 8-OH-DPAT or the 5-HT2A/C antagon ist ritanserin. HAL (1 mg/kg, SC) elicited a strong cataleptic state, reaching its maximal intensity (about 240 s) 2 h after the drug admini stration. This effect was paralleled by a long-lasting enhancement of striatal DA and DOPAC extracellular levels, reaching 230 and 350% of b asal values, respectively. 8-OH-DPAT (0.1 mg/kg, SC) given 2.5 h after , and ritanserin (0.63 and 1.25 mg/kg, IP), given 15 min prior to HAL, significantly reduced the neuroleptic-induced catalepsy. However, bot h 5-HT agents failed to modify basal DA and DOPAC striatal outflow as well as the stimulatory effect of HAL on these parameters. It can thus be concluded that the anticataleptic effect of these compounds is not related to an alteration of DA release within the striatum.