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in Journal of the American Veterinary Medical Association

Summary

Urethral smooth muscle tone in response to treatment with phenylephrine, a selective α1-adrenergic receptor agonist, and prazosin a selective α1-adrenergic receptor antagonist, was evaluated in 12 anesthetized healthy adult sexually intact male cats. Intravenous administration of prazosin (20 to 30 μg/kg of body weight) decreased the average preprostatic and prostatic intraurethral pressure, compared with baseline and postphenylephrine (20 to 30 μg/kg) administration, values. Neither prazosin nor phenylephrine administration had an effect on functional urethral length. Results have implications for the pharmacologic management of lower urinary tract disorders in male cats.

Free access
in American Journal of Veterinary Research

Summary

Effects of the neuromuscular blocking agent succinylcholine (n = 9), the centrally acting skeletal muscle relaxant diazepam (n = 11), and the direct-acting skeletal muscle relaxant dantrolene sodium (n = 8) on the urethral pressure profile were evaluated in anesthetized, healthy, sexually intact, adult male cats. Intravenous administration of succinylcholine (0.075 mg/kg of body weight) significantly decreased mean absolute pressure in the prostatic and post-prostatic/penile intraurethral segments by −9.5 and −6.5 mm of Hg, respectively (P = 0.0002 and P = 0.0006, respectively). Dantrolene (1.0 mg/kg, iv) significantly decreased mean prostatic and postprostatic/penile intraurethral segmental pressures by −3.5 and −2.8 mm of Hg, respectively (P = 0.005 and P = 0.0181, respectively). Diazepam (0.8 mg/kg, iv) did not significantly alter mean intraurethral segmental pressures. None of the drugs caused a change in segmental lengths of the urethra. These results indicate that skeletal muscle makes a substantial contribution to intraurethral tone in anesthetized, healthy, sexually intact male cats and that skeletal muscle relaxation may be successful in reducing prostatic and post-prostatic/penile urethral segmental tone in male cats. These results also suggest that dantrolene sodium may be valuable for the pharmacologic management of urethral disorders in male cats.

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To evaluate the effects of 2 compounds with α-adrenergic antagonist properties on the urethral pressures of anesthetized, healthy, sexually intact male cats, and to evaluate one of the compounds for effect on striated muscle.

Animals

20 healthy, sexually intact male cats.

Procedure

Cats were anesthetized with halothane, and urethral pressure profilometry was performed before and after treatment. 125l-labeled α-bungarotoxin bound to nicotinic receptors of murine skeletal muscle was used in a competitive binding study with acepromazine maleate.

Results

Acepromazine maleate significantly decreased intraurethral pressures in the preprostatic (19%) and pro-static (21%) regions of the urethra. There was no effect on the postprostatic/penile segment. Acepromazine did not inhibit 125l-labeled α-bungarotoxin binding to nicotinic receptors in murine skeletal muscle. Phenoxybenzamine significantly decreased intraurethral pressures (14%) in the preprostatic region of the urethra only.

Conclusions

Acepromazine maleate and phenoxy-benzamine have effects on the smooth muscle of the urethra of healthy, male cats. Acepromazine has no effect on striated muscle.

Clinical Relevance

α-Adrenergic compounds may be used in the pharmacologic management of feline urinary tract disease. (Am J Vet Res 1996;57:1497-1500)

Free access
in American Journal of Veterinary Research

SUMMARY

The effects of the skeletal muscle-relaxing drug dantrolene sodium alone, and in combination with the α1-adrenergic antagonist prazosin, on the urethral pressure profile were investigated in male cats with obstructive lower urinary tract disease. Decreases in mean segmental intraurethral pressure induced by dantrolene (n = 3) or dantrolene in combination with prazosin (n = 3) were evaluated statistically, using a paired design. Statistical analysis was applied to absolute (mm of Hg) pressure values. Intravenous administration of dantrolene alone (1 mg/ kg of body weight, n = 3) significantly decreased pressure in the postprostatic/penile urethral segment, but did not decrease prostatic urethral pressures. Dantrolene in combination with prazosin (0.03 mg/kg, iv) caused a 20% pressure decrease in the prostatic segment (P = 0.060). Preprostatic urethral pressure was not significantly affected by either treatment regimen in the small pool of cats studied. There was no difference in baseline pressures (mm of Hg) in the 3 intraurethral segments of these 6 recently obstructed male cats, compared with historic baseline pressures (mm of Hg) in the 3 intraurethral segments of 28 healthy male cats.

These results indicate that dantrolene and prazosin may be effective in relaxing intraurethral skeletal and smooth musculature in male cats clinically afflicted with obstructive lower urinary tract disease. However, it is not certain that administration of muscle relaxants would facilitate urethral catheterization and removal of the obstruction in male cats with blockage of the lower urinary tract. Strikingly, results of this study suggest that urethral muscle spasm had a minor role in these cats.

Free access
in American Journal of Veterinary Research