Antagonism in isolated equine digital vessels of contraction induced by epinephrine in the presence of hydrocortisone and an aqueous extract of black walnut (Juglans nigra)

F. D. GALEY, V. R. BEASLEY, D. J. SCHAEFFER, L. E. DAVIS

Research output: Contribution to journalReview article

9 Scopus citations

Abstract

Prazosin, isoxsuprine, and nifedipine were screened for ability to reverse contraction of isolated equine digital vascular strips produced by epinephrine (Epi) in the presence of hydrocortisone (Hc) and an aqueous extract of black walnut (Juglans nigra) (BW). Two arteries and two veins from each of three horses for each drug (n= 9) were maintained in isolated tissue baths in Krebs' bicarbonate buffer with 95% oxygen at 37°C. Six‐point Epi concentration‐response (C–R) curves were obtained for each vessel in the presence of Hc, BW, and the appropriate vehicle. This was repeated for each vessel using one of two concentrations of one of the three test drugs. Each drug and concentration combination was tested on a total of three arteries and three veins. Prazosin produced a concentration‐dependent shift of the Epi C–R curve to the right but the curve maintained the same maximum height and slope, which is consistent with competitive α1 adrenergic blockade. Isoxsuprine exhibited similar behavior, although the precise mechanism of action for isoxsuprine is unknown. Conversely, nifedipine did not shift the curve but did depress maximum contraction, suggesting a non‐competitive interaction consistent with its mechanism of calcium‐channel blockade.

Original languageEnglish (US)
Pages (from-to)411-420
Number of pages10
JournalJournal of Veterinary Pharmacology and Therapeutics
Volume12
Issue number4
DOIs
StatePublished - Dec 1989

All Science Journal Classification (ASJC) codes

  • Pharmacology
  • veterinary(all)

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