Journal of neuroendocrinology
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J. Neuroendocrinol. · Jul 1995
Neuronal activity and neuropeptide gene transcription in the brains of immune-challenged rats.
The present study investigated the effect of the acute-phase response of a systemic immune activation on the transcription of various immediate early genes (IEGs) and neuropeptides in the brain of conscious rats. One, 3, 6, 9, and 12 h after a single intraperitoneal (i.p.) administration of either the immune activator lipopolysaccharide (LPS) or the vehicle solution, adult male rats were sacrificed and their brains cut in 30-microns coronal sections. mRNA encoding the IEGs c-fos and nerve growth factor inducible-B (NGFI-B), and neuropeptides corticotropin-releasing factor (CRF), oxytocin (OT), and vasopressin (AVP) were assayed by in situ hybridization histochemistry using a 35S-labeled riboprobes. The primary transcripts [heteronuclear (hn)RNA] for these neuropeptides were also detected using intronic probe technology, and colocalization of c-fos mRNA within CRF, AVP, and OT neurons was determined by means of a combination of immunocytochemistry and in situ hybridization techniques on same the brain sections. ⋯ The signal for c-fos and NGFI-B mRNA in most of these brain nuclei reached a maximum at 3 h postinjection, declined at 6 h, and vanished 9 to 12 h after LPS treatment. In the parvocellular nucleus of the PVN, c-fos was largely expressed in CRF-immunoreactive (ir) neurons, whereas in the magnocellular part of that nucleus and in the SON, this transcript was colocalized in numerous OT-ir and few AVP-ir neurons. Relative levels of CRF mRNA in the parvocellular PVN were also significantly increased 6 h following LPS, but endotoxin did not alter the genetic expression of this stress-related neuropeptide in other brain regions.(ABSTRACT TRUNCATED AT 400 WORDS)