Stimulation of cholinergic receptor mediated secretion from the bovine adrenal medulla by neuropeptide Y.

The bovine adrenal medulla has been shown to possess binding sites for neuropeptide Y (NPY) and to release NPY in response to nicotinic receptor stimulation. Therefore we chose to investigate the influence of this peptide on adrenomedullary secretion using the retrogradely perfused bovine adrenal gland. The secretion of enkephalin-like peptides, norepinephrine and epinephrine was monitored after nicotinic cholinergic receptor stimulation in the presence and absence of NPY. NPY, alone, had no effect on secretion from the adrenal gland but produced a dose dependent increase in the secretion of enkephalin-like peptides and catecholamines when the cholinergic agonist, 1,1 dimethyl-4-phenylpiperizinium iodide, was present. The increase was significant at 1 X 10(-8) M when compared to release in the absence of NPY. The stimulatory action of other cholinergic agonists (nicotine and acetylcholine) was likewise potentiated by the addition of the neuropeptide. Peptide YY and pancreatic polypeptide did not mimic the effect of NPY when examined at the same concentration. In contrast to the potentiation observed in the perfused adrenal gland, NPY (1 X 10(-8) M) inhibited the cholinergic mediated release of enkephalin-like peptides and catecholamines from cultured bovine chromaffin cells. These data suggest that NPY may have the capacity to augment cholinergic receptor mediated secretion from the bovine adrenal gland.

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.

Plasma enkephalin-like peptide response to chronic nicotine infusion in guinea pig.

Nicotine administration, using mini-osmotic pumps, to male guinea pigs (31 micrograms/h for 10 days) resulted in a significant elevation of plasma epinephrine and enkephalin-like peptides but not norepinephrine. The increase in plasma epinephrine and enkephalin-like peptides was not accompanied by corresponding alterations in either adrenal medullary synthesis or blood pressure and heart rate. These findings may provide a partial explanation for the observation that chronic smoking does not induce hypertension.

Extraction and partial characterization of enkephalin-like peptides from splanchnic nerve.

A method is described for the extraction of enkephalin-like peptides from peripheral nerve using chloroform and acidic methanol to facilitate a differential extraction of peptides and lipid. Porcine splanchnic nerve contains enkephalin-like peptides in low amounts compared to porcine adrenal medulla and striatum. Gel filtration chromatography reveals the presence of enkephalin-like peptides in both processed and cryptic forms. This is the first reported isolation and partial characterization of these peptides in splanchnic nerve. The presence of these peptides in this nerve provides support for the contention that the splanchnic nerve can modulate catecholamine release from the adrenal medulla through an effect on opiate receptors located on chromaffin cells.