Soc. Neurosci. Abstr. 13: 465.
FUNCTIONAL ORGANIZATION OF LATERAL HYPOTHALAMIC GLUCOSE-SENSITIVE (GS) AND GLUCOSE-INSENSITIVE (GIS) NEURONS IN THE MONKEY.
Z. Karadi, Y. Oomura, H. Nishino, S. Aou and I. Fujita (SPON: K. Uchizono)
Natl. Inst. Physiol. Sci., Okazaki 444, Japan.
GS- and GIS-neurons in the lateral hypothalamic area(LHA) show characteristic neuronal responses during operant bar-press feeding tasks; i.e. the GS-neurons decrease activity during bar-press and reward phases, while the GIS-neurons increase firing to cue light and cue tone. To elucidate these neurons' input-output organization as well as their specific function in the (olfactory and gustatory information processing, LHA single unit responses to electric brain stimulations as well as to various odorants and taste solutions were studied.
Electric shocks to the dorsolateral prefrontal and premotor cortices were followed by similar activity changes of the GS- and GIS-neurons. On the other hand, the GS-neurons responded more often to electric stimulation of the orbitofrontal cortex than did the GIS-neurons, while stimulation of the motor cortex evoked firing changes in more GIS- than GS-neurons.
Odor stimuli elicited excitatory and/or inhibitory responses in almost all of the GS-neurons; however, only less than 50% of the GIS-neurons responded to smells. Manyfold olfactory responsiveness, for two or more odors, of the GS-neurons was observed, whereas the GIS-neurons responded predominantly to one specific smell only.
Gustatory stimulations resulted in firing changes of the most GS-neurons, whereas fewer responses of the GIS-neurons were seen. The GS-neurons responded prevailingly to two or more taste qualities, while the GIS-neurons did mainly to only one. The overwhelming majority of the GS-neurons showed "bimodal" responsiveness to both, gustatory and olfactory stimulations, in contrast with the GIS-neurons that responded predominantly to either taste or odor.
On the basis of the present data different functional organization of the GS- and GIS-neurons in the LHA is suggested. The GS-neurons, having strong orbitofrontal innervation, seem to integrate multimodal, mainly "internal" sensory information in regulating different mechanisms related to food intake. On the other hand, the GIS-neurons, with marked motor cortex connections, distinguish specific "external" sensory cues to modulate selection and acquisition of foods.