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C-nociceptor activation of hypothalamic neurones and the columnar organisation of their projections to the periaqueductal grey in the rat

Published online by Cambridge University Press:  08 March 2002

B. M. Lumb
Affiliation:
Department of Physiology, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
D. M. Parry
Affiliation:
Department of Physiology, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
F. M. Semenenko
Affiliation:
Department of Physiology, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
S. McMullan
Affiliation:
Department of Physiology, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
D. A. A. Simpson
Affiliation:
Department of Physiology, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
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Abstract

The induction of Fos protein was used to localise hypothalamic neurones activated by ramps of noxious skin heating delivered at a rate of 2.5 °C s-1 to preferentially activate C-nociceptors. This was combined with retrograde transport of cholera toxin subunit B from identified 'pressor' and 'depressor' sites in the dorsolateral/lateral or the ventrolateral columns of the periaqueductal grey. Fos-positive neurones were found throughout the rostral hypothalamus. Despite this wide distribution, those neurones double labelled retrogradely from the periaqueductal grey were focused in the lateral area of the anterior hypothalamus. More than 20 % of Fos-positive neurones in this region projected to depressor sites in the ventrolateral periaqueductal grey, and 10 % projected to its dorsolateral/lateral sector. These results are discussed in relation to the peripheral inputs to hypothalamic-midbrain pathways and their role in the cardiovascular responses to different components of the pain signal. Experimental Physiology (2002) 87.2, 123-128.

Type
Rapid Communications
Copyright
© The Physiological Society 2002

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