Heat acclimation and hypohydration: Involvement of central angiotensin II receptors in thermoregulation

Michal Horowitz*, Pavel Kaspler, Eckhart Simon, Ruediger Gerstberger

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

40 Scopus citations

Abstract

This investigation attempted to confirm the involvement of central ANG II-ergic signals in thermoregulation. Experiments were conducted on rats undergoing short (STHA)- and long (LTHA)-term heat acclimation, with and without superimposed hypohydration. Vasodilatation (VTsh) and salivation (STsh) temperature thresholds, taft blood flow, and heat endurance were measured in conscious rats during heat stress (40°C) before and after losartan (Los), an ANG II AT1-selective receptor antagonist, administration either to the lateral ventricle or intravenously. Heat acclimation alone resulted in decreased VTsh. STsh decreased during STHA and resumed the preacclimation value, together with markedly increased heat endurance on LTHA. Hypohydration did not affect this biphasic response, although STsh was elevated in all groups. The enhanced heat endurance attained by LTHA was blunted. Neither Los treatment affected the nonacclimated rats. In the heat- acclimated, euhydrated rats, intracerebroventricular Los resulted in decreased VTsh, whereas intravenous Los resulted in elevated STsh. Both intracerebroventricular and intravenous Los led to markedly enhanced heat endurance of the LTHA hypohydrated rats. It is concluded that the LTHA group showed a loss of the benefits acquired by acclimation on hypohydration, whereas the STHA rats, which show an accelerated autonomic excitability in that phase, gained some benefit. It is suggested that ANG II modulates thermoregulation in conditions of chronic adjustments. Central ANG II signals may lead to VTsh upshift, whereas circumventricular structures, activated via circulating ANG II, decrease STsh. On hypohydration these responses seem to be desensitized.

Original languageEnglish
Pages (from-to)R47-R55
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume277
Issue number1 46-1
DOIs
StatePublished - Jul 1999

Keywords

  • AT receptors
  • Losartan
  • Salivation
  • Vasodilatation

Fingerprint

Dive into the research topics of 'Heat acclimation and hypohydration: Involvement of central angiotensin II receptors in thermoregulation'. Together they form a unique fingerprint.

Cite this