INTRAVENOUS ADMINISTRATION OF INTERLEUKIN-1-BETA INDUCES FOS-LIKE IMMUNOREACTIVITY IN CORTICOTROPIN-RELEASING HORMONE NEURONS IN THE PARAVENTRICULAR HYPOTHALAMIC NUCLEUS OF THE RAT
Jg. Veening et al., INTRAVENOUS ADMINISTRATION OF INTERLEUKIN-1-BETA INDUCES FOS-LIKE IMMUNOREACTIVITY IN CORTICOTROPIN-RELEASING HORMONE NEURONS IN THE PARAVENTRICULAR HYPOTHALAMIC NUCLEUS OF THE RAT, Journal of chemical neuroanatomy, 6(6), 1993, pp. 391-397
It has been shown that acute administration of recombinant human inter
leukin 1 beta (IL-1) to rats elicits an activation of the pituitary-ad
renal axis. In the present study we investigated immunohistochemically
the expression of Fos-like immunoreactivity (Fos-LI) in the hypothala
mus of rats following intravenous injection of IL-1. One, 2 and 4 h af
ter IL-1 or physiological saline injections, rats were killed and perf
used, and the brains processed for Fos-immunohistochemistry. Dense pop
ulations of neurons containing Fos-LI-positive nuclei were found in th
e paraventricular hypothalamic nuclei (PVH) of IL-1-treated rats. In p
articular, the dorsal medial parvocellular part, but also some of the
other parvocellular subdivisions contained many Fos-LI neurons. Maxima
l induction of staining was found at a dose of 5 mu g/rat after 1 or 2
h survival, while immunostaining had decreased to almost control leve
ls after 4 h. No Fos-LI was found in the PVH of control aminals. Doubl
e immunocytochemical staining for Fos and corticotropin-releasing horm
one (CRH) revealed that Fos-LI was predominantly present in parvocellu
lar CRH-containing neurons of the PVH. The finding that peripherally i
njected IL- 1 induces Fos-LI in hypothalamic CRH neurons strengthens t
he hypothesis that these neurons are part of the circuitry mediating I
L- I-induced activation of the pituitary-adrenal axis.