Role of forebrain glucose-monitoring neurons in the central control of feeding: I. Behavioral properties and neurotransmitter sensitivities.
Extracellular single neuron recording experiments were performed in the lateral hypothalamic area (LHA), amygdaloid body (AMY) and globus pallidus (GP) of anesthetized rats and anesthetized or alert rhesus monkeys during microelectrophoretic administration of different neurochemicals including glucose. Neuron activity in the behaving primate was also investigated during a conditioned bar press alimentary task, as well as during presentation of food and non-food objects. In the LHA, AMY and GP specific glucose-sensitive (GS) neurons were found, as their activity were suppressed by glucose. The proportion of GS neurons was approximately 29%, 11% and 14%, respectively. The GS neurons in the monkey were especially likely to respond to phase of the conditioned alimentary task, and these same neurons appeared to be particularly influenced by sensorimotor and motivational factors. LHA, AMY and GP GS neurons displayed distinct sensitivities to various neurotransmitters applied microelectrophoretically. The present results, along with previous data, indicate that a hirearchically organized network of the brainstem and forebrain glucose-monitoring neurons exit and this system is involved in the regulation of feeding.