Circling produced by serotonin and dopamine agonists in raphe lesioned rats: a serotonin model

The serotonin (5-HT) receptor agonists quipazine and 5-methoxy-N,N-dimethyltryptamine caused slow, contralateral circling, which was not dose-related, when given to rats with an asymmetric electrolytic lesion of the midbrain medial raphe nucleus. No circling was recorded after administration of fenfluramine, a compound that releases 5-HT. The dopamine drugs apomorphine and d-amphetamine caused vigorous circling in raphe lesioned rats which was increased further by quipazine but antagonized by fenfluramine. The effects of the 5-HT drugs on d-amphetamine circling were closely dose-related. The results suggest that modulation of d-amphetamine circling by 5-HT agonists in rats with a specific, asymmetric 5-HT lesion could provide the basis for a 5-HT rotation model.