In the ventromedial nucleus of the rat hypothalamus, GABA-immunolabeled neurons are abundant and are innervated by both enkephalin- and GABA-immunolabeled axon terminals. Academic Article uri icon

Overview

abstract

  • Immunohistochemical-labeling for the neurochemicals gamma-aminobutyric acid (GABA) and enkephalin are abundant in the ventromedial nucleus of the hypothalamus (VMN). In VMN, both GABA and enkephalin may function to regulate feeding behavior, as well as other hormone-controlled behaviors. Importantly, in several brain areas, enkephalin is often thought to modulate GABAergic neurotransmission. Therefore, we used dual-labeling immunohistochemistry with electron microscopic analysis to study the circuitry of neurons containing GABA- and/or enkephalin-labeling within the VMN. Somato-dendritic profiles containing GABA-labeling were three fold more abundant than GABA-labeled axon terminals (117 soma or dendrites vs. 34 axons). In addition, axon terminals containing GABA-labeling sometimes synapsed onto GABA-labeled somata or dendrites (25% or 9/34). In contrast, under these conditions labeling for enkephalin was primarily restricted to axon terminals, which were very abundant throughout VMN. Enkephalin-containing terminals accounted for a large fraction (25% 23/92) of the axons in contact with GABA-labeled dendrites, although they also contacted unlabeled dendrites. These observations suggest that a population of VMN neurons are GABAergic. These may be either local circuit 'interneurons' or projection neurons. In addition, GABA-labeled VMN neurons may be regulated by either enkephalin or GABA. These morphologic observations provide the basis for disinhibitory mechanisms to function within the VMN.

publication date

  • January 16, 1999

Research

keywords

  • Enkephalins
  • Neurons
  • Presynaptic Terminals
  • Ventromedial Hypothalamic Nucleus
  • gamma-Aminobutyric Acid

Identity

Scopus Document Identifier

  • 0033573583

Digital Object Identifier (DOI)

  • 10.1016/s0006-8993(98)01084-1

PubMed ID

  • 9878688

Additional Document Info

volume

  • 816

issue

  • 1