Central effects of histamine on food intake, and kind of histamine receptors in sheep brain

Histamine is a well known amine which controls many physiological functions of the CNS, including; fluid balance, appetite, thermoregulation, cardiovascular control, learning and stress response. All these functions are done via three membranous H1, H2 and H3 receptors, which in laboratory animals feeding behaviour is under the control of H1 type. In order to investigate the central effect of histamine on sheep feeding behaviour and characterization of it's receptors, a Latin square test was designed using four Iranian Nainee rams which were intra-cerebroventricularly cannulated. In the first stage 12hr fasted (7PM to 7AM) rams in individual cages were infused with 0(control), 100, 400 and 800nM of histamine in turn, which each ram received each dose 4 times in different days. 10 minutes later (7AM) water and food container were put in their cages and the consumed water and food were recorded at 0.5, 1, 3 and 12hr intervals. Results of this stage revealed that histamine significantly (P<0.01) suppressed food intake in this species. Using three specific histamine antagonists; chloropheniramine, ranitidine and thioperamide in the next stage showed this suppressive effect of histamine was significantly (P<0.01) blocked by chloropheniramine. Concluding that feeding behaviour in sheep by histamine is controlled via H1 receptors.