Histamine agonist and antagonist drugs: interference with CNS control of GH release in rats

The effects of the administration into the brain ventricle of histamine, selective H1- and H2-receptor agonists and antagonists and chemically similar substances with nonspecific activity on basal and morphine-stimulated growth hormone (GH) secretion in normal male rats were studied. None of the drugs had any significant effect on baseline rat GH levels, but histamine and H1 agonists were able to decrease the rat GH release evoked by morphine. Mepyramine (H1 antagonist) had no consistent effect by itself but was effective in preventing the inhibitory action of 2-methylhistamine (H1 agonist). H2 agonists and antagonists and their chemical analogues were all inhibitory, but by a mechanism which is nonspecific and must be interpreted cautiously. These results confirm the inhibitory effect of histamine on rat GH release and indicate that H1 receptors in the CNS are responsible for this effect.