The possible involvement of galanin in the modulation of the function of rat pituitary-adrenocortical axis under basal and stressful conditions.
The effect of a s.c. bolus injection of 2 micrograms galanin on the hypothalamo-pituitary-adrenocortical (HPA) axis were investigated in both normal and ether-stressed (2 min ether-vapor inhalation) or cold-stressed (20 min at 4 degrees C) rats. Blood concentrations of ACTH, aldosterone (ALDO) and corticosterone (B) were measured by specific RIA, 1, 2 or 4 h after galanin injection. Galanin administration to normal rats resulted in a marked rise in the blood levels of ACTH, ALDO and B at 1h and 2 h, the values returned to the baseline after 4 h. Ether and cold stresses notably raised the blood levels of ACTH, ALDO and B, and these rises lasted unchanged until 4 h. Galanin markedly potentiated ACTH and ALDO responses to ether stress at 1 and 2 h, but B response remained unchanged. ACTH response to cold stress was not affected by galanin; however, galanin magnified ALDO response to cold stress at 4 h, and enhanced at 1 h and depressed at 2 h that of B. In light of these findings the following conclusions can be drawn: (i) galanin exerts a stimulatory effect on HPA axis of rats under basal conditions; (ii) under our experimental conditions, ether stress exerts a stronger stimulation of HPA axis than cold stress; (iii) the galaninergic mechanisms involved in the stimulation of ACTH release do not interfere with ether stress-activated ones controlling ACTH secretion, and are probably similar to those underlying the effect of cold stress; (iv) steroidogenic capacity of adrenal cortex, at least in term of glucocorticoid hormones, is a rate-limiting step in the response of rat HPA axis to severe stresses; and (v) galanin exerts a direct secretory action of the rat adrenal gland, that can manifest itself only in the case of submaximally cold stress-stimulated HPA axis.
Malendowicz
L K
LK
Department of Histology and Embryology, School of Medicine, Poznan, Poland.
Nussdorfer
G G
GG
Nowak
K W
KW
Mazzocchi
G
G
D000302:Adrenal Cortex; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000450:Aldosterone / Q000097:blood; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D005260:Female; D019004:Galanin; D009479:Neuropeptides / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology*; D010913:Pituitary-Adrenal System / Q000187:drug effects* / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D012016:Reference Values; D013312:Stress, Physiological / Q000097:blood / Q000503:physiopathology*
D001786:Blood Glucose; D009479:Neuropeptides; D010455:Peptides; D000450:Aldosterone; D019004:Galanin; D000324:Adrenocorticotropic Hormone