Induction of oral dryness and endocannabinoid

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This study was to clarify a relationship between endocannabinoid and thirst sensation. Male Wistar rats were used in the experiment. First, the effects of endocannabinoids on IPSCs of neurons of the subfornical organ (SFO), which is a thirst center of the brain, recorded from brain slice preparations were investigated with patch clamp method. The CB1 receptor agonist WIN 55,221-2 (WIN) decreased significantly the frequency but not the amplitude of IPSCs. The effect was disappeared with the CB1 antagonist. Next, the endocannabinoids on neural activity of the SFO were investigated with the multi-electrode array (MEA) method. Application of the endocannabinoid anandamide and WIN affected unit activities in only the small number of neurons. The i.c.v. injection of WIN had no effects on water and salt intakes. These suggest that while endocannabinoids affect GABA release in the SFO, they do not play any important role in induction of thirst sensation, if present, in the normal condition.