Histamine and serotonin independently elicit drinking in the rat.
Drinking elicited by SC histamine or serotonin (5-HT) was studied in Sprague-Dawley male rats following 0.9% NaCl or combined antagonism of H1 and H2 histamine receptors using dexbrompheniramine (DXB) and cimetidine (C), or following antagonism of 5-HT receptors using methysergide (M). Histaminergic antagonism using IP 1 mg/kg DXB plus 16 mg/kg C abolished drinking elicited by SC 2.5 mg/kg histamine, but it failed to inhibit drinking elicited by the ED50 or by the ED100 for SC 5-HT in the same rats. Serotonergic antagonism using IP 3 mg/kg M abolished drinking elicited by SC 0.63 mg/kg 5-HT, but it failed to inhibit drinking elicited by the ED50 or by the ED100 for SC histamine in the same rats. These findings demonstrate that activation of peripheral 5-HT receptors is not necessary for SC histamine to elicit drinking and that activation of peripheral histamine receptors is not necessary for SC 5-HT to elicit drinking. This demonstrates that histamine and 5-HT activate different receptors to elicit drinking in the rat. The finding that the ED50 for histamine and the ED50 for 5-HT are not additive in their effects on drinking is consistent with the notion that a single mechanism mediates the dipsogenic effects of SC histamine and SC 5-HT in the rat.
D000818:Animals; D002927:Cimetidine / Q000494:pharmacology; D004327:Drinking Behavior / Q000187:drug effects*; D004347:Drug Interactions; D006632:Histamine / Q000494:pharmacology*; D008784:Methysergide / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011969:Receptors, Histamine H1 / Q000187:drug effects; D011970:Receptors, Histamine H2 / Q000187:drug effects; D011985:Receptors, Serotonin / Q000187:drug effects; D012701:Serotonin / Q000494:pharmacology*; D013268:Stimulation, Chemical
D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D011985:Receptors, Serotonin; D012701:Serotonin; D002927:Cimetidine; D006632:Histamine; D008784:Methysergide