effect of verapamil on brain monoamines of rats pretreated with nialamide and reserpine

ABSTRACT

The present work investigated the acute effect of verapamil on the brain levels of 5-hydroxytryptamine [5HT], dopamine [DA] and noradrenaline [NA] in nialamide and reserpine pretreated rats. Results showed that treatment of rats with verapamil [5 mug/kg] one hour prior to sacrifice significantly increased brain 5HT and decreased DA brain level. However, brain NA level showed no significant difference compared to control values. Treatment of rats with nialamide, significantly increased brain 5HT, DA and NA levels. In nialamide pretreated rats, verapamil [5 mug/kg] revealed a highly significant increase was slightly higher than that produced by either verapamil or nialamide alone, it did not reach statistical significance. Moreover, pretreatment of rats with nialamide completely blocked the verapamil-induced decrease in brain DA level. On the other hand, the treatment of rats with reserpine, significantly depleted brain 5HT, DA and NA levels. The verapamil-induced increase in brain 5HT was blocked by the pretreatment of rats with reserpine. However, reserpine pretreatment revealed a synergistic effect with the calcium antagonist on brain DA level, where a highly significant depletion was evident. The possible mechanisms by which verapamil induced these changes in brain monoamines was discussed