Ventromedial hypothalamus lesions increase the dipsogenic responses and reduce the pressor responses to median preoptic area activation

Physiol Behav. 1997 Aug;62(2):311-6. doi: 10.1016/s0031-9384(97)88986-x.

Abstract

In this study, we investigated the participation of adrenergic receptors of the median preoptic area (MnPO) and the participation of ventromedial hypothalamus (VMH) in angiotensin II-(ANG II)-induced water intake and pressor responses. Male rats with sham or electrolytic VMH lesions and a stainless steel cannula implanted into the MnPO were used. Noradrenaline, clonidine (an alpha2-adrenergic receptor agonist), or phenylephrine (an alpha1-adrenergic receptor agonist) injected into the MnPO of sham-lesioned rats reduced water ingestion induced by ANG II injected into the same area. In VMH-lesioned rats ANG II-induced water intake increased with a previous injection of noradrenaline, phenylephrine, or isoproterenol. The pressor response induced by ANG II injected into the MnPO was reduced in VMH-lesioned rats, whereas the pressor response induced by clonidine was abolished. Previous treatment with noradrenaline and phenylephrine into the MnPO of sham-lesioned rats produced a pressor response, and a hypotensive response was obtained with the previous administration of noradrenaline, phenylephrine or isoproterenol into the MnPO of VMH-lesioned rats. These results show that VMH is essential for the dipsogenic and pressor responses induced by adrenergic and angiotensinergic activation of the MnPO in rats.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic alpha-Agonists / administration & dosage
  • Adrenergic alpha-Agonists / pharmacology
  • Adrenergic beta-Agonists / administration & dosage
  • Adrenergic beta-Agonists / pharmacology
  • Angiotensin II / administration & dosage
  • Angiotensin II / antagonists & inhibitors
  • Angiotensin II / pharmacology*
  • Animals
  • Blood Pressure / drug effects
  • Blood Pressure / physiology*
  • Catheterization
  • Clonidine / administration & dosage
  • Clonidine / pharmacology
  • Drinking Behavior / drug effects
  • Drinking Behavior / physiology*
  • Electrodes, Implanted
  • Isoproterenol / administration & dosage
  • Isoproterenol / pharmacology
  • Male
  • Microinjections
  • Norepinephrine / administration & dosage
  • Norepinephrine / pharmacology
  • Phenylephrine / administration & dosage
  • Phenylephrine / pharmacology
  • Preoptic Area / drug effects
  • Preoptic Area / physiology*
  • Rats
  • Vasoconstrictor Agents / administration & dosage
  • Vasoconstrictor Agents / antagonists & inhibitors
  • Vasoconstrictor Agents / pharmacology*
  • Ventromedial Hypothalamic Nucleus / physiology*

Substances

  • Adrenergic alpha-Agonists
  • Adrenergic beta-Agonists
  • Vasoconstrictor Agents
  • Angiotensin II
  • Phenylephrine
  • Isoproterenol
  • Clonidine
  • Norepinephrine