COLOCALIZATION OF PEPTIDE-LIKE IMMUNOREACTIVITIES WITH GLUCOCORTICOIDRECEPTOR-LIKE AND FOS-LIKE IMMUNOREACTIVITIES IN THE RAT PARABRACHIALNUCLEUS

The parabrachial nucleus (PB) is a brainstem nucleus, which mediates a utonomic information from the viscera to various forebrain nuclei, e.g . to the central nucleus of the amygdala (ACe) and to the medial preop tic area (MPOA). The neurons of the PB contain several neuropeptides, of which calcitonin-gene related peptide-immunoreactive (CGRP-IR) and neurotensin (NT)-IR neurons provide input to the ACe, whereas corticot ropin-releasing factor-IR (CRF) neurons project to the MPOA. The aim o f the present paper was to study whether the neurons containing CGRP-, NT- and CRF-like immunoreactivities (LIs) in the PB also contain gluc ocorticoid receptor (GR)- and/or Fos-LIs after stress. No co-localizat ion was observed with the GR-LI and peptide-LIs, suggesting that plasm a glucocorticoids do not have direct effects on these neurons of the P B. After stress, the vast majority of the peptide-IR perikarya exhibit ed Fos-LI, suggesting that the peptidergic pathways from the PB to ACe and MPOA are activated in stress. The ACe and MPOA have been connecte d in various stress related responses, e.g. inhibiting the hypothalamo -pituitary-gonadal axis, raising the blood pressure and pulse, and inc reasing the secretion of glucocorticoids. Therefore, the activation of the peptidergic pathways between the PB and the ACe and MPOA suggests that some of these responses may be elicited by the peptidergic input from the PB. Furthermore, since Fos acts as a transcription factor, s tress may affect the expression of the neuropeptides studied.