HISTAMINE IS A POWERFUL STIMULATOR OF CYCLIC-AMP FORMATION IN CHICK PINEAL-GLAND

Histamine(HA) potently stimulated both basal and forskolin-activated c AMP formation in chick pineal gland. The action of HA was mimicked by 4-methyl-HA, and to some extent by 2-methyl-HA and 2-thiazolylethylami ne (2TEA), but not by dimaprit, (R)-alpha-methyl-HA tele-methyl-HA and several other imidazole-derivatives. The stimulatory actions of all t he compounds were antagonized by ranitidine and tiotidine (HA H-2-rece ptor antagonists), and were not affected by mepyramine and thioperamid e (HA H-1- and H-3-receptor blockers, respectively). These data indica te that the chick pineal probably contains H-2-like HA receptors, whos e stimulation leads to increases in cAMP production.