Endocrinology, Vol 129, 2049-2057, Copyright © 1991 by Endocrine Society
Influence of the paraventricular nucleus of the hypothalamus in the alteration of neuroendocrine functions induced by intermittent footshock or interleukin
S Rivest and C Rivier
Clayton Foundation Laboratories for Peptide Biology, Salk Institute, La Jolla, California 92037.
The documented ability of physical stress and cytokines to increase the
secretion of corticotropin-releasing factor CRF by the paraventricular
nucleus of the hypothalamus (PVN), coupled with our earlier demonstration
that CRF acts within the brain to interfere with reproductive functions,
led us to investigate the effect of lesions of the PVN on LH, testosterone,
ACTH, and corticosterone (CORT) secretion. Bilateral lesions of the PVN
were done electrolytically, and 2 weeks later a series of acute and chronic
experiments were performed in intact or castrated male rats bearing
indwelling jugular and/or intracerebroventricular cannulas. The first study
involved a single 2-h exposure of intact male rats to footshocks (2 mA,
2-sec duration, 4 per min). Although PVN lesions did not measurably alter
the ability of intermittent footshock to lower plasma testosterone levels,
this treatment attenuated the rise in plasma ACTH and CORT. In a second
study, which was done in castrated rats, shocks were delivered 2 h daily
for 7 days, and circulating hormone levels were measured at the end of the
last shock period. Plasma LH levels of stressed rats showed statistically
comparable decreases in both sham- and PVN-lesioned animals. Chronic
exposure to footshocks induced smaller increases of ACTH and CORT secretion
in PVN-lesioned compared to sham-lesioned rats, but the lesions did not
completely abolish stress-induced activation of the hypothalamic-pituitary
adrenal (HPA) axis. The third experiment involved the central injection of
the vehicle or 40 ng interleukin-1 beta (IL-1 beta) to castrated rats. As
expected, IL-1 beta dramatically decreased plasma LH values and increased
circulating ACTH and CORT levels measured 2 h later. Bilateral PVN lesion
did not influence LH secretion after injection of the vehicle or IL-1 beta.
In contrast, destruction of the PVN completely blocked the increase of HPA
axis activity observed in sham-operated rats 2 h after the
intracerebroventricular infusion of IL-1 beta. These results confirm our
previous observation that exposure to either footshocks or interleukins
alters the activity of the hypothalamic-pituitary gonadal and HPA axis.
Additionally, the present studies suggest that the PVN, which represents
the predominant hypothalamic nucleus controlling the response of the HPA
axis to a number of stimuli, does not appear to be necessary for the
antireproductive effects of intermittent footshock or immune activation.