Jz. Nowak et B. Sek, STIMULATORY EFFECT OF HISTAMINE ON CYCLIC-AMP FORMATION IN CHICK PINEAL-GLAND, Journal of neurochemistry, 63(4), 1994, pp. 1338-1345
Histamine (HA) potently stimulated cyclic AMP accumulation in intact p
ineal glands taken from light-exposed chicks. The action of HA was str
onger in the presence of forskolin and the phosphodiesterase inhibitor
3-isobutyl-1-methylxanthine (IBMX). The effect of HA was mimicked by
HA H-1- and H-2-receptor-selective agonists in the following order of
potency: HA > 4-methylhistamine (H-2) > 2-methylhistamine (H-1) > 2-th
iazolylethylamine (H-1) much greater than dimaprit (H-2) The HA H-3-re
ceptor-selective agonist (R)alpha-methylhistamine was poorly active. T
he effect of HA was antagonized by selective H-2-receptor blockers (ti
otidine > oxmetidine > cimetidine = ranitidine) and was not significan
tly affected by the selective H-1- and H-3-receptor blockers mepyramin
e and thioperamide. A detailed analysis of an antagonistic action of r
anitidine (versus HA) revealed a noncompetitive mode of action of the
H-2 blocker. The stimulatory action of the H-1 agonist 2-thiazolylethy
lamine (both under basal conditions and in the presence of forskolin o
r IBMX) was not significantly influenced by three H-1-receptor-selecti
ve blockers (mepyramine, triprolidine, and diphenhydramine), but it wa
s totally counteracted by ranitidine. Using accepted selective agonist
s and antagonists of the HA H-1, H-2, and H-3 receptor we were unable
to identify clearly the receptor subtype mediating the HA action on th
e cyclic AMP-generating system of the chick pineal. It is suggested th
at the receptor under consideration may represent either an H-2-like (
in terms of mammalian criteria) or avian-specific HA receptor. The dat
a suggest that HA may be considered a modulator of the pineal activity
in chicks.