Co-release of Neuropeptide Y and Catecholamines Upon Adrenal Activation in the Cat

The release of neuropeptide Y (NPY)-like immunoreactivity (-LI) in relation to catecholamines from the cat adrenal was studied in anaesthetized animals. Abdominal surgery increased plasma levels of NPY-LI from 65 +/- 6 to 149 +/- 26 pmol l-1. A positive veno-arterial concentration gradient over the adrenal gland was found for both NPY-LI, adrenaline (Adr) and noradrenaline (NA) during basal conditions. Asphyxia for 2 min increased the output of both NPY-LI and catecholamines from the adrenal. Electrical stimulation of the splanchnic nerve caused a marked increase in adrenal output of NPY-LI and catecholamines. The adrenal content of NPY-LI, as well as the release of NPY-LI from the adrenal, was at least 1000-fold lower on a molar basis than that of catecholamines. The concentration of NPY-LI in the adrenal vein upon splanchnic nerve stimulation was in the nM range. Reversed-phase HPLC characterization revealed that NPY-LI in the adrenal, and in the adrenal venous plasma collected during splanchnic nerve stimulation, was closely related to synthetic porcine NPY. Stimulation with bursts of 20 Hz for 1 S with 10 s intervals for 2 min caused a four-fold higher output of NPY-LI and Adr compared to a continuous stimulation with 2 Hz, giving the same number of impulses. The NA output, however, was only slightly increased by burst stimulation. Guanethidine did not reduce the adrenal output of NPY-LI or catecholamines induced by splanchnic nerve stimulation, while the release was abolished by chlorisondamine.(ABSTRACT TRUNCATED AT 250 WORDS)