Corelease of neuropeptide Y like immunoreactivity with catecholamines from the adrenal gland during splanchnic nerve stimulation in anesthetized dogs

Abstract

The release of neuropeptide Y like immunoreactivity (NPY-li) from the adrenal gland was studied in relation to the secretion of catecholamines (CA:NE, norepinephrine; E, epinephrine) during the left splanchnic nerve stimulation in thiopental–chloralose anesthetized dogs (n = 16). Plasma concentrations of NE, E, and NPY-li were determined in the left adrenal venous and aortic blood. Adrenal outputs of NPY-li, NE, and E were 2.4 ± 0.4, 1.4 ± 0.2, and 7.3 ± 1.7 ng/min, under basal conditions, respectively. These values increased significantly (p < 0.05; n = 8) in response to a continuous stepwise stimulation at frequencies of 1, 3, and 10 Hz given at 3-min intervals during 9 min, reaching a maximum output of 4.6 ± 0.9 (NPY-li), 240.2 ± 50.2 (NE), and 1412.5 ± 309.7 ng/min (E) at a frequency of 10 Hz. Burst electrical stimulation at 40 Hz for 1 s at 10-s intervals for a period of 10 min produced similar increases (p < 0.05) in the release of NPY-li (4.8 ± 1.0 ng/min, n = 8), NE (283.5 ± 144.3 ng/min, n = 8), and E (1133.5 ± 430.6 ng/min, n = 8). Adrenal NPY-li output was significantly correlated with adrenal NE output (r = 0.606; n = 24; p < 0.05) and adrenal E output (r = 0.640; n = 24; p < 0.05) in dogs receiving the burst stimulation. The present findings demonstrate that NPY-li is coreleased with NE and E from the adrenal gland in response to direct splanchnic nerve stepwise or burst stimulation at high frequencies in anesthetized dogs. It is thus possible that the adrenal medullary NPY-li contributes to the modulation of circulating NPY-li levels under various physiopathological conditions.Key words: adrenal medulla, burst stimulation, catecholamines, corelease, neuropeptide Y, splanchnic nerves.