Journal of Neuroscience, Vol 8, 2780-2787, Copyright © 1988 by Society for Neuroscience
Interactions between the lateral hypothalamus and the periaqueductal gray
MM Behbehani, MR Park and ME Clement
Department of Physiology and Biophysics, University of Cincinnati, College of Medicine, Ohio 45267.
Anatomical and physiological experiments were conducted to characterize the
interactions between the lateral hypothalamus (LH) and the periaqueductal
gray (PAG) and to determine the role of neurotensin in their interaction.
Anatomical studies using injection of Phaseolus vulgaris leucoagglutinin
into the LH showed an extensive projection to the ventromedial and the
ventrolateral PAG and a less dense projection to the medial and dorsal
parts of this region. Physiological experiments were performed on both
deeply and lightly anesthetized animals. Electrical stimulation of the LH
caused excitation of PAG cells with an onset latency of approximately 14
msec. There was a strong correlation between the response of PAG cells to
electrical stimulation and injection of glutamic acid into the LH.
Electrical or chemical stimulation of the LH produced an increase in tail
flick latency in the lightly anesthetized animals that outlasted the
stimulation period. There was a strong correlation between the response of
PAG cells to electrical and chemical stimulation of the LH and their
response to pressure-injected neurotensin. It is concluded that an
excitatory projection from the LH to PAG exists which may involve
neurotensin. This pathway may be involved in the analgesia produced by LH
stimulation.