Effects of neuropeptide y on food intake, glycemia and pancreatic secretion in the lizard podarcis s. sicula in early spring

Abstract

In early spring, neuropeptide Y injections in the lizard Podarcis s. sicula caused an increase of appetite in animals compared with those injected with saline alone. Glycemia determination showed an annual cycle with a maximum of blood glucose in summer when animals feed, and a minimum in winter when they undergo a semi-hibernation period during which they do not eat. In NPY-treated lizards, blood glucose dropped as the NPY dose increased to reach significantly lower values than those of controls fed for the whole time of treatment. Both endocrine and exocrine pancreas was affected by the treatment. In particular, the insulin immunoreactive B cells appeared less intensely immunostained than those of the controls, with a progressive reduction of immunostaining, according to the NPY doses used. Optical density of immunostaining measurements of B cells, showing a progressive reduction of this parameter in the treated lizards, supported the morphological observations. Acinar cells, too, exhibited reduced immunostaining when tested for carboxypeptidase. Taken together, the findings suggest that exogenous NPY stimulated an increase of food intake, and basal insulin secretion, but lowered blood glucose by a direct and/or indirect mechanism via insulin secretion. © 2004 Taylor & Francis Group, LLC.