Cardiac effects of injections of epinephrine into the spinal intermediolateral column

V. K. Malhotra, A. Kachroo, H. N. Sapru

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

Small doses of epinephrine (0.008, 0.05, and 0.1 pmol, i.e., 20-nl volumes of 0.40, 2.5, and 5 μM solutions) produced a dose-dependent increase in heart rate when microinjected into the right intermediolateral column (IML) at T2 spinal level. These effects were mediated via α1-adrenergic receptors because prazosin blocked them. The presence of α1-adrenergic receptors at this site was confirmed by microinjections of phenylephrine (a specific agonist for these receptors); phenylephrine elicited tachycardia. Larger doses of epinephrine (320, 2,000, and 3,200 pmol, i.e., 20-nl volumes of 16, 100, and 160 mM solutions) caused bradycardia when microinjected into the IML. These effects were mediated via α2-adrenergic receptors because idazoxan blocked them. The presence of α2-adrenergic receptors at this site was confirmed by microinjections of clonidine (a specific agonist for these receptors); clonidine elicited bradycardia. Injections of the vehicle (20 nl of normal saline containing 0.3% ascorbic acid, pH 7.4) did not evoke a response. Epinephrine, prazosin, or idazoxan did not alter the responses to L-glutamate. None of the doses of epinephrine elicited any response when injected intravenously. The aforementioned results provide pharmacological evidence for the presence of α1-and α2-adrenergic receptors in the IML at T2. Thus a basis is provided for investigating the role, if any, of α- adrenergic receptors in the IML in mediating cardiovascular responses elicited by the stimulation of different brain stem areas.

Original languageEnglish (US)
Pages (from-to)H633-H641
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume265
Issue number2 34-2
DOIs
StatePublished - 1993

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

Keywords

  • L-glutamate
  • Wistar rat
  • blood pressure
  • heart rate
  • idazoxan
  • phenylephrine
  • prazosin

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