This increase in CORT is necessary for glucocorticoid type II receptor function, gene expression, and protein synthesis necessary to cope with any ensuing challenges to physiological and behavioral homeostasis. The increase in the plasma CORT during the sleep-to-wake transition coincides with the acrophase of hypothalamic-pituitary-adrenal (HPA) axis activity. However, despite considerable importance, the specific role of the LC in the modulation of many neuronal and physiological functions remains to be elucidated. The sleep-to-wake transition is also accompanied by tandem increases in cardiovascular tone and plasma glucocorticoids, corticosterone (CORT) in rat and cortisol in humans. As a major component of the reticular activating system, the LC modulates alertness, attention, arousal, sleep-wake cycle, and diurnal/circadian activity patterns. Neurons in the rostral region projecting toward forebrain and those in the ventral regions projecting toward spinal cord impart a functional dichotomy of the LC-NA system. ![]() The LC neurons are organized along the rostral-ventral extent of the nucleus. It projects the full length of the neuroaxis with extensive projections to cortical regions and the spinal cord. The locus coeruleus (LC), the A6 noradrenergic (NA) cell group, is located in the dorsal rostral part of the brain stem on the lateral floor of the fourth ventricle. The importance of increases in plasma corticosterone at acrophase to maintain short- and long-term cardiovascular homeostasis is discussed. The integrity of the LC-NA system is important to maintain blood flow dynamics. ![]() Conclusion: LC-NA modulation of diurnal and stress-induced HPA axis reactivity occurs via distinct neurocircuits. Results: In DSP rats compared to SAL rats, (1) regional brain norepinephrine was decreased, but there was no change in median eminence or olfactory bulb CRF content (2) during HPA axis acrophase, the plasma corticosterone response was blunted (3) after hemorrhage and air puff-startle, the plasma adrenocorticotropic hormone response was attenuated, whereas the corticosterone response was dependent on stressor category (4) under basal conditions, hemodynamic measures exhibited altered blood flow dynamics and systemic vasodilation and (5) after hemorrhage, hemodynamics exhibited asynchronous responses. ![]() On day 16, brain regions from a subset of rats were dissected for norepinephrine and corticotropin-releasing factor (CRF) assay. HPA axis activity, diurnally (circadian) and after stress (transient hemorrhage or air puff-startle), and basal and post-hemorrhage hemodynamics were evaluated. On day 10, animals were surgically prepared with jugular vein (hypothalamic-pituitary-adrenal axis) or carotid artery (hemodynamics) catheters and experiments performed on day 14. Methods: Male rats, on day 0, were treated intraperitoneally with either DSP4 (50 mg/kg body weight) (DSP), an LC-NA specific neurotoxin, or normal saline (SAL). These studies evaluate the role of the LC in this corticosterone and cardiovascular response. Introduction: Activation of the locus coeruleus-noradrenergic (LC-NA) system during awakening is associated with an increase in plasma corticosterone and cardiovascular tone.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |