Inhibitory effects evoked from the anterior hypothalamus are selective for the nociceptive responses of dorsal horn neurons with high- and low-threshold inputs

Journal of Neurophysiology
B J Workman, B M Lumb

Abstract

The aim of the present study was to examine the selectivity of descending control of nociceptive information in the spinal dorsal horn following neuronal activation at "pressor" sites in the anterior hypothalamus. Extracellular single-unit activity was recorded from 11 dorsal horn neurons in the lower lumbar spinal cord of anesthetized rats. Neurons selected for investigation were those that responded to noxious (pinch and radiant heat >46 degrees C) and nonnoxious (prod, stroke, and/or brush) stimulation within their cutaneous receptive fields on the ipsilateral hind paw. These are referred to as Class 2 neurons. Micropipettes were inserted stereotaxically into the anterior hypothalamus at sites where injection of the excitatory amino acid L-homocysteic acid (L-HCA) evoked increases in arterial blood pressure. The effects of microinjection of L-HCA at "pressor" sites in the anterior hypothalamus were then tested on the responses of Class 2 neurons to noxious and nonnoxious stimulation of their excitatory receptive fields. The high-threshold (pinch and/or radiant heat) responses of 7/7 Class 2 neurons tested were inhibited by an average of 66.3 +/- 8.8% (mean +/- SE) by neuronal activation at hypothalamic pressor sites. The low...Continue Reading

References

May 1, 1992·Brain Research. Brain Research Reviews·A Randich, G F Gebhart
Apr 1, 1988·Journal of Neurophysiology·S B McMahon, P D Wall
Jan 1, 1984·Neuroscience and Biobehavioral Reviews·A Randich, W Maixner

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Citations

Jun 21, 2007·Headache·Philip Holland, Peter J Goadsby
Jun 13, 2008·Cephalalgia : an International Journal of Headache·A May
May 30, 2002·Progress in Neurobiology·Mark J Millan

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