L. Debeljuk et A. Bartke, IMMUNOREACTIVE SUBSTANCE-P AND NEUROKININ-A IN THE HYPOTHALAMUS AND ANTERIOR-PITUITARY GLAND OF SIBERIAN-HAMSTERS AND SYRIAN-HAMSTERS AND OF RATS, Journal of Reproduction and Fertility, 101(2), 1994, pp. 427-434
In this investigation the concentrations of immunoreactive substance P
and neurokinin A in the hypothalamus and anterior pituitary of the Si
berian hamster were compared with those in the rat and Syrian hamster.
The concentrations of immunoreactive neurokinin A in the hypothalamus
of Siberian hamsters were significantly higher than those of: rats an
d Syrian hamsters, while male Siberian hamsters had similar amounts of
substance P in the hypothalamus to those of male Syrian hamsters, but
had higher amounts than those in male rats. However, female Siberian
hamsters had significantly higher hypothalamic concentrations of both
substance P and neurokinin A than did female Syrian hamsters and rats.
In the anterior pituitary glands of Siberian hamsters, concentrations
of substance P and neurokinin A were markedly higher than they were i
n rats and even more so than in Syrian hamsters. Ovariectomy further i
ncreased tachykinin concentrations in the anterior pituitary gland of
female Siberian hamsters, and this was completely prevented by oestrad
iol replacement. Female Siberian hamsters kept under conditions of red
uced photoperiod had significantly higher tachykinin concentrations in
the anterior pituitary than did animals kept under daily photoperiods
of 16 h light:8 h dark. The incubation of anterior pituitaries from f
emale Siberian hamsters with a neurokinin A receptor antagonist result
ed in a partial blockade of the LH and FSH release in response to LHRH
. Thus, the high concentration of tachykinins present in the anterior
pituitary of the Siberian hamster may have a local role in modulating
the secretion or release of gonadotrophins.