Effect of intracerebroventricular injection of histamine HI and H2 antagonists on food intake in freely feeding and food-deprived rabbits

ABSTRACT

To investigate the role of central histamine HI and H2 receptors on food intake in freely feeding and food - deprived rabbits. Experimental study. Forty - two male New Zealand white rabbits weighing between 2.5 - 3 Kg. A 23- gauge, 18mm long stainless steel guide cannula was surgically implanted into the lateral ventricle of brain. Intracerebroventricular injections of normal saline [control], promethazine and ranitidine at the same doses of 50, 100 and 200 microg /rabbit in a volume of 5 microl were performed using a 25 micro1 Hamilton's syringe. Cumulative food intake was measured in freely feeding and food - deprived rabbits at the 0.5, 1, 2, 3, 6 and 24h after injections. Paired t-test, Factorial ANOVA and Duncan's test. Food deprivation for 16h increased 0.5,1,2, 3 and 6h cumulative food intake. In freely feeding rabbits, promethazine [50 microg] had no effect on food intake, and at the dose of 100 microag increased 1 and 2h feeding after injection, but at the dose of 200 microag increased 2 and 3h post-injection food intake. In the 16h food- deprived rabbits promethazine [50,100 and 200 microg] had no effect. Ranitidine at the doses of 50,100 and 200 microg produced no significant changes on food intake in both freely feeding and food- deprived rabbits. Promethazine did not exert any significant effects on the 6 and 24h post- injection food intake. Based on the results of the present study it is concluded that the blockade of central HI but not H2 receptors induce a short- lasting excitatory effect on food intake. Thus, central HI receptor may have an important role in the central control of feeding behavior