Jz. Nowak et al., A BIZARRE RECEPTOR MEDIATING STIMULATORY EFFECT OF HISTAMINE ON CYCLIC-AMP FORMATION IN DUCK PINEAL-GLAND, Neuroscience letters, 202(1-2), 1995, pp. 65-68
In agreement with our previous findings in chick pineal, histamine als
o appeared to be a potent stimulator of cAMP formation in intact duck
pineal gland (about ten-fold increase above control at 100 mu M), show
ing an EC(50) Value of 3-5 mu M. The effect of histamine in the duck p
ineal was mimicked by several histaminergic drugs, with the following
order of potency: histamine = 4-methylhistamine > 2-methylhistamine >
R-alpha-methylhistamine > amthamine > 2-thiazolylethylamine = immepip
> imetit > dimaprit. The effect of 100 mu M histamine was unaffected b
y H-1-, H-2- and H-3-receptor selective antagonists, mepyramine, ranit
idine and thioperamide, respectively; yet, two other H-2-antagonists,
aminopotentidine and tiotidine, reduced the histamine effect by only 4
0%. Thus, these results, being in line with our previous chick data, g
ive support to a suggestion that histamine may be considered a modulat
or of the pineal activity, and that the avian pineal may contain a nov
el or avian-specific histamine receptor modulating cAMP formation, who
se pharmacology is different from that typical for H-1-, H-2-, or H-3-
type receptor.