Journal of Neurophysiology, Vol 53, Issue 1 17-31, Copyright © 1985 by APS
Selective inhibition of glucose-sensitive neurons in rat lateral hypothalamus by noxious stimuli and morphine
S. K. Sikdar and Y. Oomura
On the basis of their responsiveness to electrophoretically applied
glucose, neurons in the lateral hypothalamic area (LHA) have been
characterized as either glucose sensitive or glucose nonsensitive.
Glucose-sensitive neurons are important in feeding control (4, 36-38, 44,
54). The aim of this study was to increase understanding of the
neurophysiological mechanisms involved in the disturbance of feeding by
pain. Radiant heating of the scrotum, strong tail pinch, and immersion of
the tail in hot water were used as noxious stimuli. In order to correlate
the responses of LHA neurons to noxious inputs with possible local release
of endogenous opiates, effects of electrophoretically applied morphine and
naloxone were also tested. The effects of glucose, morphine, and noxious
stimulation were studied in a total of 165 neurons recorded from 75 adult
male urethane-chloralose-anesthetized rats. Of 52 neurons determined to be
glucose sensitive, 36 (69%) were inhibited by both noxious stimulation and
morphine. A majority of the glucose-nonsensitive neurons did not respond to
either morphine or noxious stimulation (87/113, 74%). The relation of
glucose sensitivity to inhibition by pain and/or morphine was statistically
significant (Fisher's exact probability test, P less than 0.01). Naloxone
attenuated the inhibitory effects of both pain and morphine, thus
suggesting mediation of both by the same neuronal mechanism. From this
evidence we conclude that LHA glucose-sensitive neurons are involved in the
suppression of feeding by noxious stimulation.
