Ll. Badura et Bd. Goldman, SEASONAL REGULATION OF NEUROENDOCRINE ACTIVITY IN MALE TURKISH HAMSTERS (MESOCRICETUS-BRANDTI) - ROLE OF THE HYPOTHALAMIC PARAVENTRICULAR NUCLEUS, Neuroendocrinology, 55(4), 1992, pp. 477-484
Male Turkish hamsters received horizontal knife cuts within the hypoth
alamus to investigate the role of afferent and efferent projections of
the paraventricular nucleus (PVN) in seasonal regulation of endocrine
function. Following surgery, the animals were exposed to either a lon
g (16 h light/8 h dark) or a short (8 h light/16 h dark) photoperiod.
Similar to pinealectomy, knife cuts placed ventral to the PVN, so as t
o disrupt transfer of photic information to the pineal gland, resulted
in a rapid decline in circulating prolactin (PRL) and follicle-stimul
ating hormone (FSH) levels, as well as a reduction in testicular size,
under both long- and short-photoperiod conditions. In contrast, knife
cuts placed just dorsal to the PVN, 50 as to leave connections to the
pineal gland intact, did not prevent the effects of short-day exposur
e on PRL secretion; however, short-day induced declines in FSH levels
and testicular size were largely prevented by these lesions. The prese
nt results are consistent with past findings that the integrity of the
neural pathway to the pineal gland is necessary for the maintenance o
f appropriate reproductive responses to photoperiod in seasonal mammal
s. They further indicate a dissociation between the role of hypothalam
ic connections in the photoperiod-dependent secretion of two anterior
pituitary hormones, i.e., PRL and FSH, and suggest that release of the
se hormones may depend upon different neural pathways for their expres
sion.