Facilitation of baroreflex-induced bradycardia by stimulation of specific hypothalamic sites in the rat

B. J. Pardini, Kaushik P Patel, P. G. Schmid, D. D. Lund

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Hypothalamic stimulation generally inhibits baroreflex-induced bradycardia. However, we have noted discrete areas of the rat hypothalamus which facilitate reflex bradycardia. The effects of hypothalamic stimulation on baroreflex-induced changes in heart rate were investigated in urethane-anesthetized rats (1.2 g/kg, i.p.; n = 6) instrumented with femoral arterial and venous catheters. Bipolar electrodes (250 μm diameter) were implanted stereotaxically in the hypothalamus. Baroreflex-induced bradycardia was elicited by phenylephrine (PE) injection (8-20 μg/kg). Responses to stimulation (STIM) (50-150 μA, 80 Hz, 0.5 ms), PE, and Stim + PE were studied for 1 min. In the ventral medial and anterior hypothalamus. STIM caused transient increases in blood pressure and no changes in heart rate. Peak blood pressure was lower during STIM + PE than during PE (144 ± 5 vs 164 ± 3 mm Hg; P < 0.05). However, STIM + PE resulted in a lower heart rate compared to PE (194 ± 22 vs 270 ± 17 bpm; P < 0.05). At 1 min, the heart rate in STIM + PE rats remained lower than in PE rats (205 ± 37 vs 319 ± 16 bpm; P < 0.05). Atropine administration indicated that the facilitation was primarily parasympathetic in nature. These results identify specific hypothalamic regions which facilitate baroreflex-induced bradycardia by parasympathetic mechanisms.

Original languageEnglish (US)
Pages (from-to)274-281
Number of pages8
JournalBrain Research
Volume384
Issue number2
DOIs
StatePublished - Oct 8 1986

Fingerprint

Baroreflex
Phenylephrine
Bradycardia
Heart Rate
Hypothalamus
Middle Hypothalamus
Blood Pressure
Anterior Hypothalamus
Urethane
Thigh
Atropine
Reflex
Electrodes
Catheters
Injections

Keywords

  • Anterior hypothalamic area
  • Baroreflex
  • Heart rate
  • Parasympathetic nervous system
  • Ventromedial nucleus of the hypothalamus

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

Cite this

Facilitation of baroreflex-induced bradycardia by stimulation of specific hypothalamic sites in the rat. / Pardini, B. J.; Patel, Kaushik P; Schmid, P. G.; Lund, D. D.

In: Brain Research, Vol. 384, No. 2, 08.10.1986, p. 274-281.

Research output: Contribution to journalArticle

Pardini, B. J. ; Patel, Kaushik P ; Schmid, P. G. ; Lund, D. D. / Facilitation of baroreflex-induced bradycardia by stimulation of specific hypothalamic sites in the rat. In: Brain Research. 1986 ; Vol. 384, No. 2. pp. 274-281.
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