Effect of Ritanserin on the Circling Movement in the Unilateral Substantia Nigra-Lesioned Rats

Kim, In Ho; Chung, Young Chul; Eun, Hong Bai

Abstract

OBJECTIVE
Recently, the serotonin-dopamine interaction is being regarded as a possible mechanism for both less extrapyramidal symptoms and good therapeutic effect on negative symptoms which are outstanding advantages of atypical antipsychotics. The goal of the study was to further define serotonin dopamine interaction in three different brain area of rats ; prefrontal cortex, striatum and nucleus accumbens. METHOD: The rats used in this study weighed 150-300gm. Under the aesthesia with pentothal sodium(25 mg/kg), stainless steel cannula was inserted in the right substantia nigra according to atlas(Paxinous and Watson) and 6-OHDA was injected at the rate of 1 mul/min to make a unilateral substantia nigra lesion. A week later, apomorphine (s. c. 0.1 mg/kg) was injected through the cannula and the rats with circling behavior counting more than 200 for an hour were selected for the study. Three weeks after that, the rats were further divided into 3 groups according to the brain area that permanent stainless steel cannula was implanted : prefrontal cortex group, striatum group and nucleus accumbens group. Within each group comparison was done between the number of circling behavior obtained by the injection of vehicle plus apomorphine and the one obtained by the injection of ritanserin plus apomorphine. Wilcoxon signed ranks test was used in data-analysis.
RESULTS
The effect of ritanserin on the circling behavior in prefrontal cortex was absent but in striatum and nucleus accumbens, increasing effect was noted.
CONCLUSIONS
It might be suggested that serotonin has an inhibitory control on dopaminergic function in striatum and nucleus accumbens.