EFFECTS OF HISTAMINE H-1 RECEPTORS ON THE FEEDING AND DRINKING PATTERNS IN PYGMY GOATS

The goal of these experiments was to determine which histamine recepto rs are involved in the relationship between drinking and feeding in ru minants. To this end, the effects of the histamine receptor antagonist s dexbrompheniramine (H-1 receptor antagonist), cimetidine (H-2 recept or antagonist), and terfenadine (H-1 receptor antagonist) on feeding a nd drinking patterns of pygmy goats were investigated. Two experiments using dexbrompheniramine [1 and 2 mg/kg of body weight (BW)(0.75)], t wo experiments using cimetidine (16 and 32 mg/kg of BW0.75), and two e xperiments using terfenadine (5 and 11.5 mg/kg of BW0.75) were perform ed to assess the type and location (periphery or central nervous syste m) of the histamine receptors involved in the mediation of prandial dr inking by pygmy goats. The H-1 receptor antagonists dexbrompheniramine (2 mg/kg of BW0.75) and terfenadine (11.5 mg/kg of BW0.75) significan tly reduced water intake, but cumulative feed intake did not change. C onsequently, the ratio of water intake to feed intake decreased. In co ntrast, the H-2 receptor antagonist did not affect either water or fee d intake. Dexbrompheniramine at 2 mg/kg of BW0.75 and terfenadine at 1 1.5 mg/kg of BW0.75 also decreased draft frequency and decreased the w ater intake associated with meals. Results showed that blockage of per ipheral H-1 histamine receptors attenuates the association between wat er and feed intake in pygmy goats. Therefore, the stimulating effect o f feed intake on water intake appears to depend on activation of perip heral H-1 histamine receptors.