Abstract
Stressful stimuli induced by immobilization are perceived as acute stress in rats. This acute stress activates corticotropin-releasing hormone (CRH) neurons in the hypothalamic paraventricular nucleus (PVN), resulting in stimulation of the hypothalamic-pituitary-adrenal (HPA) axis. The ventral ascending noradrenergic bundles (V-NAB) from the brainstem innervate the PVN. To investigate the relationship between the response of the HPA axis and the V-NAB, we examined changes in plasma corticosterone, the final output of the HPA axis, and extracellular noradrenaline (NA) in the PVN following immobilization stress in rats that received bilateral 6-hydroxydopamine (6-OHDA) lesions of the V-NAB. 6-OHDA microinjection into the V-NAB reduced the magnitude of the responses of plasma corticosterone and extracellular NA in the PVN following immobilization stress. Our results suggest that V-NAB innervation of the PVN is involved in immobilization stress-induced activation of the HPA axis.
Highlights
Stressful stimuli activate neurons in the hypothalamic paraventricular nucleus (PVN), which produce and release corticotropin-releasing hormone (CRH) [1]
We investigated the role of the ventral ascending noradrenergic bundles (V-NAB) in the response of the HPA axis to immobilization stress using 6-hydroxydopamine (6-OHDA), a specific and long-lasting catecholamine neurotoxin
Six days after bilateral 6-OHDA microinjection into the V-NAB, the NA concentration in the PVN was significantly decreased by 77.5% and 77.1% compared with vehicle microinjection and the control, respectively (8.67 ± 2.75 pg/μg protein for rats injected with 6-OHDA vs. 38.83 ± 5.83 pg/μg protein for rats injected with vehicle vs. 37.83 ± 3.59 pg/μg protein for the unmanipulated control; p < 0.01; one-way analysis of variance (ANOVA) with post-hoc Bonferroni testing)
Summary
Stressful stimuli activate neurons in the hypothalamic paraventricular nucleus (PVN), which produce and release corticotropin-releasing hormone (CRH) [1]. CRH induces the anterior pituitary to secrete adrenocorticotropic. How to cite this paper: Yoshihara, T. and Yawaka, Y. (2015) The Ventral Ascending Noradrenergic Bundles Are Involved in the Stress Response to Immobilization in Rats. Journal of Behavioral and Brain Science, 5, 88-95. Yawaka hormone (ACTH), which in turn stimulates the adrenal cortex to secrete plasma corticosterone as the final output of the hypothalamic-pituitary-adrenal (HPA) axis. The PVN plays an important role in the regulatory mechanisms of the endocrine and autonomic systems and in adaptive behavior to a stressful environment [2]
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