GABA in the paraventricular nucleus tonically suppresses baroreflex function

Alterations during pregnancy

Mollie C. Page, Priscila A. Cassaglia, Virginia Brooks

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

It is well established that GABAergic inputs to the paraventricular nucleus of the hypothalamus (PVN) tonically suppress heart rate and the activity of several sympathetic nerves. However, whether GABA similarly inhibits PVN control of baroreflex function has not been previously investigated. To test this hypothesis, it was determined whether microinjection of the GABAa antagonist, bicuculline, into the PVN enhances the baroreflex in anesthetized female virgin rats. In addition, because GABAergic inhibition of PVN preautonomic neurons is decreased during pregnancy, it was also determined whether the effects of PVN bicuculline administration on baroreflex function were less in pregnant animals. In virgin rats, PVN microinjection of bicuculline increased (P <0.05) baroreflex gain and maximum levels of heart rate (gain, from 1.6 ± 0.6 to 3.8 ± 1.3 bpm/mmHg; maximum, from 406 ± 18 to 475 ± 14 bpm) and of lumbar sympathetic nerve activity (gain from 2.6 ± 0.7 to 4.8 ± 1.6%/ mmHg; maximum, 149 ± 32 to 273 ± 48%), indicating that PVN GABA normally suppresses baroreflex function. Pregnancy decreased heart rate baroreflex gain (pregnant, 0.9 ± 0.3 bpm/mmHg; virgin, 1.9 ± 0.2 bpm/mmHg; P <0.05). Following PVN bicuculline administration in pregnant rats, smaller (P <0.01) increments in baroreflex gain (pregnant, 0.6 ± 0.1 bpm/mmHg; virgin, 2.4 ± 0.9 bpm/mmHg) and maximum (pregnant, 33 ± 7 bpm; virgin, 75 ± 12 bpm; P <0.05) were produced. Collectively, these data suggest that the PVN normally inhibits the baroreflex via tonic GABAergic inputs and that this inhibition is less during pregnancy.

Original languageEnglish (US)
Pages (from-to)1452-1458
Number of pages7
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume300
Issue number6
DOIs
StatePublished - Jun 2011

Fingerprint

Baroreflex
Paraventricular Hypothalamic Nucleus
gamma-Aminobutyric Acid
Hypothalamus
Pregnancy
Bicuculline
Heart Rate
Microinjections
Neurons

Keywords

  • γ-aminobutyric acid
  • Baroreceptor reflex
  • Heart rate
  • Lumbar sympathetic nervous system

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

Cite this

GABA in the paraventricular nucleus tonically suppresses baroreflex function : Alterations during pregnancy. / Page, Mollie C.; Cassaglia, Priscila A.; Brooks, Virginia.

In: American Journal of Physiology - Regulatory Integrative and Comparative Physiology, Vol. 300, No. 6, 06.2011, p. 1452-1458.

Research output: Contribution to journalArticle

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