Abstract
Occlusal disharmony induced by placing an acryl cap on the lower incisors of rats is perceived as chronic stress. This chronic 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 extracellular noradrenaline (NA) in the PVN and plasma corticosterone, the final output of the HPA axis, following occlusal disharmony in rats injected with 6-hydroxydopamine (6-OHDA), a specific catecholamine neurotoxin. 6-OHDA microinjection into the V-NAB reduced the magnitude of the responses of extracellular NA in the PVN and the plasma corticosterone to occlusal disharmony. Our results suggest that V-NAB to the PVN are involved in occlusal disharmony-induced activation of the HPA axis.
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