Vasopressinergic, oxytocinergic, and somatostatinergic neuronal activity after adrenalectomy and immobilization stress.
Twenty days after bilateral adrenalectomy (ADX) or immediately after the last of three 6-h long immobilization periods, the levels of hypothalamic and neurohypophyseal L-[35S]Cys-labeled arginine vasopressin (AVP), oxytocin (OT), and somatostatin-14 (SRIF) (only stressed animals) were measured simultaneously in male Wistar rats, after third ventricular administration of the labeled precursor, via guide-cannulae. The acetic acid-extracted labeled peptide fractions were purified by two sequential HPLC steps. After a 4 h period of labeling, only L-[35S]Cys-AVP was selectively increased in the hypothalami of ADX-ized rats, compared to the sham-operated animals, possibly reflecting a significant activation of the paraventricular parvocellular (PVC) AVP/corticotropin-releasing factor (CRF) neurons. The increased accumulation of neurohypophyseal L-[35S]Cys-labeled AVP and OT in these animals, without changes in the endogenous levels of these peptides, as measured by UV absorbance, also suggests a moderate activation of the magnocellular (MGC) AVP and OT neurons, as a consequence of adrenal insufficiency. In response to immobilization stress, levels of L-[35S]Cys-OT were selectively increased in the hypothalami and corresponding neurohypophyses, 2 h and 4 h after receiving the label, concomitantly with a statistically significant reduction in the stores of OT in the neural lobes. AVP and SRIF biosynthesis remained unaffected by immobilization; the neurohypophyseal AVP stores likewise remained unchanged. These observations suggest the selective activation of MGC-OT neurons in response to chronic immobilization stress. Selective increases in hypothalamic L-[35S]Cys-AVP in ADX-ized rats, and in hypothalamic L-[35S]Cys-OT in chronically stress-immobilized rats, are presented as a measure of PVC-AVP/CRF and MGC-OT neuronal activation, respectively.
Franco-Bourland
R E
RE
Department of Biochemistry, Instituto Nacional de la Nutrición, Salvador Zubirán, México, DF, México.
D000315:Adrenalectomy; D000818:Animals; D001127:Arginine Vasopressin / Q000096:biosynthesis*; D003346:Corticotropin-Releasing Hormone / Q000096:biosynthesis; D003545:Cysteine / Q000378:metabolism; D007700:Kinetics; D008297:Male; D009474:Neurons / Q000378:metabolism*; D010121:Oxytocin / Q000096:biosynthesis*; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism*; D010904:Pituitary Gland, Posterior / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012149:Restraint, Physical; D013004:Somatostatin / Q000096:biosynthesis*; D013315:Stress, Psychological / Q000503:physiopathology*; D013462:Sulfur Radioisotopes
D013462:Sulfur Radioisotopes; D001127:Arginine Vasopressin; D010121:Oxytocin; D013004:Somatostatin; D003346:Corticotropin-Releasing Hormone; D003545:Cysteine