Beta-adrenergic and opioidergic modulation of cortisol secretion in response to acute stress

The modulatory action of beta-adrenergic and opioidergic pathways on the cortisol response to acute stressors was investigated using gonadectomized male miniature pigs. Three types of stressors, nose-snare (NS, for 2 min. each on four occasions at 30 min. intervals); high intensity cracker blasts (CB, two blasts at 3 min intervals) and ACTH (1 i.u./kg BW, i.v.) were utilized 80 min after start of blood sampling. For assessment of cortisol blood samples were withdrawn every 20 min for 200 min. In addition, animals received i.v. injections of either isoproterenol (5 microg/ kg) or propranolol (0.5 mg/kg) or naloxone (1 mg/kg) 15 or 30 min before the application of stressor. Stress of repeated NS application as well as ACTH treatment, resulted in immediate secretion of cortisol (p<0.001). Blast of crackers resulted in a transient increase in cortisol (p<0.05). Isoproterenol stimulated the basal cortisol secretion for about 20 min in unstressed pigs (p <0.01) but propranolol had no effects. Isoproterenol also reinforced (p<0.05) the effect of CB, but had no effect on the cortisol response to nose-snare. In contrast, response to NS was reduced (p=0.02) by propranolol. Neither isoproterenol nor propranolol altered the cortisol response to ACTH application. Pretreatment with naloxone significantly increased the cortisol response to NS (p<0.01) and to CB (p<0.01), but had no effects on ACTH-induced cortisol release. In conclusion, the beta-adrenergic involvement is evident in the cortisol response to acute stress of nose-snare. Furthermore, the results indicate that activation of endogenous opioid system during stress mitigates adrenal response.