Influence of social isolation and 6-OHDA lesion on the effects of quinelorane.

The sensitivity of the response to the preferential dopaminergic D3 (DAD3) receptor agonist, quinelorane, was compared in mice housed socially and in mice isolated for 4 weeks. Quinelorane (1, 5, 10, 50 and 100 microg/kg) was administered intraperitoneally. Motor activity was measured for 60 min posttreatment. Rectal temperature was measured prior to and 1 h following the administration of quinelorane (10, 50 and 100 microg/kg i.p.). Quinelorane significantly and dose-dependently decreased locomotor activity in social and in isolated mice. The locomotor activity of isolated mice was significantly lower than that of social mice, but isolation had no effect on quinelorane-induced hypomotility. Quinelorane decreased dose-dependently rectal temperature in isolated and social mice, but isolation had no effect on quinelorane-induced decrease in rectal temperature. The lesions of dopaminergic terminals with intracerebroventricular administration of 6-OHDA decreased the dopamine (DA) level by 93% in the nucleus accumbens and by 91% in the corpus striatum; these lesions impaired neither the hypolocomotion nor the hypothermia induced by quinelorane. Thus, it may be concluded that social isolation has no influence on the quinelorane-induced decreases in rectal temperature and in locomotor activity and that the DA receptors involved in these effects of quinelorane are located postsynaptically.