Visceroendocrine responses elicited by neuropeptide Y in the nucleus tractus solitarius.

Neuropeptide Y (NPY) has been shown to be localized in a number of CNS regions, including the nucleus tractus solitarius (NTS). In this meeting report, a brief overview is presented of recent studies from our laboratory examining the role of NPY in NTS-mediated mechanisms of cardiorespiratory and visceroendocrine regulation. Microinjections of NPY, NPY analogs, or C-terminal NPY fragments were made into the subpostremal NTS of anesthetized spontaneously breathing rats. NPY elicited pronounced dose-related depressor responses, bradycardia, and reductions in respiratory minute volume. The overall cardiorespiratory response pattern elicited by NPY was mimicked by NPY, a fragment of NPY exhibiting selective agonist properties at presynaptic Y2 receptors, whereas the Y1 receptor-selective analog, [Leu31,Pro34]NPY, and the C-terminal inactive fragment, NPY, were found to be ineffective. In an effort to further characterize intrinsic NTS mechanisms mediating the NPY-evoked response pattern, NPY microinjections were similarly made in a group of rats with bilateral glossopharyngeovagotomy (G-vagotomy) and in a group of rats decerebrated at the supracollicular level. The results showed that whereas decerebration did not appreciably affect the NTS-mediated cardiorespiratory responses elicited by NPY, G-vagotomy enhanced the NPY-evoked hypotension while at the same time abolishing the NPY-evoked bradycardia and reductions in tidal volume. Taken together, these observations with G-vagotomized animals, along with the results from microinjection studies using selective ligands for NPY receptors, suggest that NPY may modulate primary visceral afferent information via activation of Y2 receptors distributed at presynaptic sites in the subpostremal NTS.(ABSTRACT TRUNCATED AT 250 WORDS)