Effect of the presynaptic dopaminergic agonist, quinpirole, on the drinking responses of rats to angiotensin II, isoproterenol, and hypertonic saline.

The dopamine (DA2) agonist, quinpirole hydrochloride (LY 171555), has been reported to inhibit central presynaptic release of norepinephrine, an effect similar to that of clonidine, an alpha 2-adrenoceptor agonist. Since clonidine exerts an antidipsogenic effect on all types of laboratory-induced drinking, the objective of these experiments was to determine whether administration of quinpirole hydrochloride produced a similar effect. The drinking responses of rats to administration of angiotensin II (200 micrograms/kg, SC), isoproterenol (25 micrograms/kg, SC), and hypertonic saline (1 M NaCl, 1% of body weight, IP) were blocked by administration of quinpirole hydrochloride (7.5 mg/kg, IP). When administered alone, quinpirole had no effect on water intake. Thus, the antidipsogenic effect of quinpirole hydrochloride resembles that of clonidine and suggests that release of norepinephrine occurs centrally at some point along the final common pathway for drinking in rats.