A massive neuronal system was detected by immunocytochemistry and radioimmunoassay with antibodies to neuropeptide Y, the recently isolated peptide of the pancreatic polypeptide family. Immunoreactive cell bodies and fibers were most prevalent in cortical, limbic, and hypothalamic regions. Neuropeptide Y was extracted in concentrations higher than those of any other peptide hitherto discovered in the mammalian brain. Column chromatography of brain extracts and double immunostaining experiments indicate that neuropeptide Y is the endogenous brain peptide responsible for immunostaining of pancreatic polypeptide-like immunoreactivity in the mammalian brain.

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SUMMARYThe current investigation, for which ethical permission was obtained, was designed to assess the putative neurophysiological effects of low intensity (9 6 J/cm2) laser (830 nm) irradiation upon conduction latencies in the human median nerve in vivo. Antidromic nerve conduction studies were performed on the non-dominant arms of healthy human volunteers (n = 51), who were each assigned to one of a variety of laser, placebo or control groups under randomized, blinded conditions. Analysis of negative peak latency differences using analysis of variance showed small (-0 4 ms) but significant increases in latencies as a result of direct laser irradiation, and, where two-site recording was used, distal to the site of irradiation. No such differences were seen in the other experimental groups. These results show that laser irradiation applied to intact skin at the parameters used here may produce a direct, localized effect upon conduction in underlying nerves.

Neuropeptide Y (NPY) and peptide YY (PYY) are two structurally related peptides. PYY has been identified within endocrine cells and NPY within nerves of the gastrointestinal tract. Infusion of PYY at a low dose at a nominal rate of 2 pmol/kg/min resulted in an increment of 59.2 ± 7.1 pmol/l in plasma concentration and a significant delay in gastric emptying of glucose. Infusion of NPY at the same rate produced similar plasma concentrations (52.5 ± 1.1 pmol/l) and had no significant effect on the rate of gastric emptying.