Premium
Stress and Interleukin‐1 β‐Induced Activation of c‐ fos , NGFI‐B ann CRF Gene Expression in the Hypothalamic PVN: Comparison Between Sprague‐Dawley, Fisher‐344 and Lewis Rats
Author(s) -
Rivest Serge,
Rivier Catherine
Publication year - 1994
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.1994.tb00559.x
Subject(s) - medicine , endocrinology , immediate early gene , parvocellular cell , c fos , hypothalamus , corticotropin releasing hormone , in situ hybridization , central nucleus of the amygdala , amygdala , gene expression , biology , chemistry , gene , biochemistry
Various signals are known to activate the hypothalamic‐pituitary‐adrenal (HPA) axis, an event largely dependent on the release of corticotropin‐releasing factor (CRF) which originates mainly from the parvocellular paraventricular nucleus (PVN) of the hypothalamus. These signals include neurogenic stimuli such as exposure to mild electroshocks, and systemic stimuli like administration of cytokines. The HPA axis activity of Lewis rats has been reported to be hyporesponsive to such stimuli, but the exact mechanisms involved in this phenomenon are poorly understood. The present study investigated the effect of footshock exposure and central injection of interleukin (IL)‐1β, on CRF neuronal activity and gene expression in the PVN of adult male Sprague‐Dawley (SD), Fisher‐344 (F344) and Lewis (LEW) rats. The animals were deeply anesthetized and rapidly perfused transcardially with a solution of 4% paraformaldehyde 3 h after the beginning of the footshock session (1.5 mA, 2 s duration, 4/min over 1 h), or the i.c.v. injection of IL‐1β (100 ng in 10 μl). mRNA encoding the immediate ‘early’ genes (lEGs) c‐fos and NGFI‐B, as well as CRF, were assayed by in situ hybridization histochemistry, while the localization of Fos protein within CRF‐immunoreactive (ir) neurons in the PVN was determined using a dual immunostaining protocol. Both stress and IL‐1β induced robust Fos‐ir expression within the parvocellular division of the PVN in all 3 strains. The number of cells immunoreactive for both Fos and CRF proteins in the PVN was similar in SD, F344 and LEW rats following either challenge. While control animals did not display detectable levels of c‐fos or NGFI‐B mRNA in the PVN, both treatments induced significant expression of these transcripts in this hypothalamic nucleus and no significant differences were observed among SD, F344 and LEW rats. Relative levels of CRF mRNA in the PVN were also significantly and comparably increased following either stress or central IL‐1β treatment. In contrast, plasma ACTH and corticosterone levels were significantly higher in F344 and SD rats than in LEW animals during the stress session. These results provide further evidence that physical stress and central IL‐1β can enhance expression of several lEGs, as well as CRF, within the parvocellular division of the PVN. These independent indices of functional activation within parvocellular CRF neurons appear to respond similarly to diverse challenges in adult male SD, F344 and LEW rats. Thus, these findings suggest that the hyporesponsiveness of LEW HPA axis to stress does not seem to be a consequence of a defect in afferent signals to the parvocellular PVN, at least in mature male rats.