Abstract
Corticotropin-releasing hormone (CRH) and vasopressin (AVP) neurons, in the paraventricular nucleus of the hypothalamus (PVN), are the principal regulators of the hypothalamic-pituitary-adrenal (HPA)-axis. AVP is primarily a neurohypophysial hormone but is co-expressed in the parvocellular CRH neurons. We sought to characterize the responses of hypothalamic neuroendocrine neurons to stressors and elucidate the implication of brain stem catecholaminergic neurons in the stress response. First, the time course profiles of AVP gene expression, as determined by in situ hybridization using either intronic or exonic probe, were disclosed to be different, depending on the nature of the imposed stressors, in contrast to rather uniform expression profiles of the CRH gene. Second, a large population of both CRH- and AVP neurons became Fos positive in the PVN after hemorrhagic shock, as determined by immunocytochemistry. However, approximately 40% of the tyrosine hydroxylase (TH)-containing neurons in the nucleus of the solitary tract (NTS) became Fos positive, thus, a discrete population of the NTS catecholaminergic neurons were activated after the stress. Third, a mouse line, heterozygous for a mutated TH gene, was introduced to examine whether catecholamine deficiency affects responsiveness of the HPA-axis to stressors. The CRH gene expression patterns were different between the TH (+/+) and TH (+/-) mice following forced swim stress, confirming the implication of the catecholaminergic system in the transmission of stress responses. [Jpn J Physiol 54 Suppl:S26 (2004)]
