Distribution of neuropeptide Y-like immunoreactive perikarya and processes in the medulla of the cat

Abstract

Neuropeptide Y-like immunoreactive (NPY-LI) perikarya and processes have been identified in the medulla of the cat. NPY-LI perikarya were found in 4 regions; (1) the medial N. of the solitary tract (MNTS), (2) the lateral tegmental field (LTF), (3) the ventrolateral medullary surface (VLMS), and (4) in the spinal trigeminal nucleus. Tyrosine hydroxylase-like immunoreactive (TH-LI) neurons were also found in the first 3 regions noted above. NPY-LI and TH-LI neurons had a similar morphology and distribution. NPY-LI and TH-LI neurons were counted in sections from 3 representative levels of the medulla. NPY-LI cells were most numerous in the LTF, especially at the level of the area postrema and more rostrally. The lowest number of NPY-LI cells was seen in the MNTS, particularly at a level caudal to the area postrema. NPY-LI cells were at least 3-fold less numerous than TH-LI cells at all levels of the MNTS, but there was a 27-fold greater number of TH-LI neurons at a level of MNTS caudal to the area postrema. In the LTF, NPY-LI cells were 2- to 5-fold less common than TH-LI cells. Approximately equal numbers of NPY-LI and TH-LI cells were counted in the VLMS at the level of the area postrema and rostrally. These data indicate that the majority of TH-LI cells in the MNTS of the cat probably do not contain NPY as a co-transmitter.(ABSTRACT TRUNCATED AT 250 WORDS)