Neuropeptide Y release from the adrenal medulla after cholinergic receptor stimulation

Peripheral nerves as well as chromaffin cells have been shown to contain neuropeptide Y (NPY), a 36 amino acid peptide that exhibits potent stimulatory actions on vascular smooth muscle. Because NPY-like immunoreactive material (NPY-IR) is stored in chromaffin granules we chose to investigate, using the retrogradely perfused bovine adrenal gland, whether nicotinic cholinergic receptor stimulation results in the secretion of this material. In addition we monitored the release of [Met5]-enkephalin-like immunoreactive material (ME-IR), which has been demonstrated to be released from the bovine adrenal medulla. NPY-IR and ME-IR were measured using antisera prepared from hemocyanin conjugates of the peptides. Increasing concentrations of acetylcholine (1 X 10(-6) M-5 X 10(-5) M), infused in the presence of 1 X 10(-5) M physostigmine, produced significant increases in NPY-IR and ME-IR release. Hexamethonium (5 X 10(-4) M) antagonized the release of both of these substances, whereas atropine (5 X 10(-7) M) did not. The role of the nicotinic cholinergic receptor in this process was established further by examining the effects of 1,1-dimethyl-4-phenylpiperazinium. Increasing concentrations of 1,1-dimethyl-4-phenylpiperazinium (1 X 10(-6) M-5 X 10(-5) M) also stimulated the release of NPY-IR and ME-IR. Analysis of the perfusate by reverse phase liquid chromatography revealed the presence of four peaks of NPY-IR. A major peak coeluted with authentic NPY. These data demonstrate that NPY-IR can be released through stimulation of the nicotinic cholinergic receptor. The adrenal medulla appears to be one of the sources for circulating NPY-IR.