Jb. Zawilska et al., THE PRESENCE OF HISTAMINE AND TELE-METHYLHISTAMINE IN THE PINEAL-GLAND OF CHICK, Acta Neurobiologiae Experimentalis, 56(3), 1996, pp. 691-695
The levels of histamine (HA) and tele-methylhistamine (t-MeHA) in chic
k pineal gland were measured by RIA at two time points, i.e. at the en
d of the light (L) phase and in the middle of the dark (D) phase of 12
h: 12 h L:D cycle. The chick pineal gland showed high HA levels (12.1
9 and 13.09 ng/pineal at L and D, respectively). The t-MeHA content of
chick pineal gland was about 20-times lower than HA level (650.2 and
536.4 pg/pineal at L and D, respectively). An aminoacid precursor of H
A, L-histidine (1 g/kg, ip), given to chicks during L or D significant
ly increased both HA and t-MeHA content of the pineal gland. The L-his
tidine-evoked elevations in HA level were 2-4-times higher than change
s in t-MeHA content. Enzymatic study showed the presence in chick pine
al of a moderate activity of L-histidine decarboxylase (HDC), and well
expressed activity of HA-methyltransferase (HMT), HA synthesizing and
inactivating enzyme, respectively, which suggests that both HA and t-
MeHA may be produced within the gland. It is suggested that the metabo
lic dynamics of the pineal HA may be higher during lighthours than dar
khours of the daily light:dark illumination cycle.