In vivo Infusion of Adrenaline Stimulates Corticotropin‐Releasing Hormone‐Producing Neurons when given Centrally but not Distally

Abstract

Abstract There is evidence that adrenaline stimulates the release of corticotropin-releasing hormone (CRH-41) from hypothalamic neurons. This study was carried out to ascertain the effects of adrenaline on the perikarya and/or distal terminals of these cells. All experiments were performed on unrestrained rats having chronic intracerebroventricular cannulas in the lateral ventricle or intracerebral cannulas in the paraventricular nucleus and, additionally, a push-pull median eminence cannula. Adrenaline (1.4 mug adrenaline bitartrate in 5 muI vehicle for intracerebroventricular infusion, or 0.7 mug in 0.25 muI for intracerebral infusion) was infused over 2 min, and 15-min median eminence perfusate samples were collected over 2 to 3 h. In another experiment the median eminence was directly perfused for 30 min with a total of 1.2 mug (n = 4) or 12 mug (n = 3) adrenaline per rat. Intracerebroventricular or intracerebral adrenaline induced a swift, short-lived (15 min) CRH-41 surge which reached 7 to 10 times the basal level. Direct perfusion of the median eminence with adrenaline (around the nerve endings of CRH-41-producing neurons) did not stimulate CRH-41 release and higher amine concentrations even tended to depress the neuropeptide release. The stimulatory effect of adrenaline on the corticotropic axis appears, therefore, to be restricted to the central dendro-perikaryal region of CRH-41-producing neurons.