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This Article Full Text Full Text (PDF) All Versions of this Article: 93/1/64    most recent expphysiol.2007.039560v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Cham, J. L. Articles by Badoer, E. Search for Related Content PubMed PubMed Citation Articles by Cham, J. L. Articles by Badoer, E. Related Collections Cardiovascular control

¹ School of Medical Sciences, RMIT University, Melbourne, Victoria, Australia

A major integrative site within the brain for autonomic function is the hypothalamic paraventricular nucleus (PVN). Several studies have suggested that the PVN may be involved in the responses regulating body temperature. Hyperthermia elicits redirection of blood flow from the viscera to the periphery and involves changes in sympathetic nerve activity mediated by the central nervous system. The hypothalamic PVN includes neurones that project to the rostral ventrolateral medulla (RVLM), an important autonomic region involved in the tonic regulation of sympathetic nerve activity. This pathway could contribute to the cardiovascular changes induced by hyperthermia. The PVN has a high concentration of nitrergic neurones and it is known that nitric oxide within the brain mediates heat dissipation. Thus the aims of this study were to determine whether RVLM-projecting neurones in the PVN are activated by heat and whether those neurones are also nitrergic. The results show that, compared with control conditions, exposure of conscious rats to a hot environment of 39°C significantly increased the number of neurones containing a Fos-positive nucleus (a marker of activation) and significantly increased the number of activated RVLM-projecting neurones in the PVN. Also, although heating significantly increased the number of activated nitrergic PVN neurones, triple-labelled neurones (i.e. activated, nitrergic and RVLM projecting) in the PVN were rarely observed. The results suggest that RVLM-projecting neurones in the PVN may play a role in responses to heat exposure but these are not nitrergic.

(Received 15 July 2007; accepted after revision 5 September 2007; first published online 7 September 2007)
Corresponding author E. Badoer: School of Medical Sciences, RMIT University, PO Box 71, Bundoora 3083, Melbourne, Victoria, Australia. Email: emilio.badoer{at}rmit.edu.au