Histamine H3 receptor-mediated modulation of water consumption in the rat.

The effect of the selective H3 receptor agonist (R)-alpha-methylhistamine and antagonist thioperamide on water consumption in the rat were examined. (R)-alpha-Methylhistamine (0.1-20 mg.kg-1 i.p.) evoked a dose-dependent increase in water consumption the maximum effect being 310 +/- 23% (n = 67) above the vehicle control response. Thioperamide (0.2,2 and 10 mg.kg-1 i.p.) alone had no effect on water consumption. However, the stimulatory effect of (R)-alpha-methylhistamine on water consumption was antagonised by thioperamide in a dose-dependent manner, whereas the H1 receptor antagonist mepyramine and the H2 receptor antagonist loxtidine were without effect. It is therefore concluded that the H3 receptor may play a role in the regulation of water consumption in the rat.