Effects of histamine H1 receptors on the feeding and drinking patterns in pygmy goats.

The goal of these experiments was to determine which histamine receptors are involved in the relationship between drinking and feeding in ruminants. To this end, the effects of the histamine receptor antagonists dexbrompheniramine (H1 receptor antagonist), cimetidine (H2 receptor antagonist), and terfenadine (H1 receptor antagonist) on feeding and drinking patterns of pygmy goats were investigated. Two experiments using dexbrompheniramine [1 and 2 mg/kg of body weight (BW)0.75], two experiments using cimetidine (16 and 32 mg/kg of BW0.75), and two experiments using terfenadine (5 and 11.5 mg/kg of BW0.75) were performed to assess the type and location (periphery or central nervous system) of the histamine receptors involved in the mediation of prandial drinking by pygmy goats. The H1 receptor antagonists dexbrompheniramine (2 mg/kg of BW0.75) and terfenadine (11.5 mg/kg of BW0.75) significantly reduced water intake, but cumulative feed intake did not change. Consequently, the ratio of water intake to feed intake decreased. In contrast, the H2 receptor antagonist did not affect either water or feed intake. Dexbrompheniramine at 2 mg/kg of BW0.75 and terfenadine at 11.5 mg/kg of BW0.75 also decreased draft frequency and decreased the water intake associated with meals. Results showed that blockage of peripheral H1 histamine receptors attenuates the association between water and feed intake in pygmy goats. Therefore, the stimulating effect of feed intake on water intake appears to depend on activation of peripheral H1 histamine receptors.