Comparison of the effects of nadolol and bisoprolol on the isoprenaline-evoked dilatation of the dorsal hand vein in man

AIMS

We attempted to explore the possible differential involvement of beta-adrenoceptor subtypes in the dilator response of the human dorsal hand vein to isoprenaline by examining the ability of bisoprolol, a selective beta1-adrenoceptor antagonist, and nadolol, a nonselective beta1/beta2-adrenoceptor antagonist, to antagonize the response.

METHODS

Twelve healthy male volunteers participated in four weekly sessions. In the preliminary session a dose-response curve to the vasoconstrictor effect of phenylephrine was constructed and the dose producing 50-75% maximal response was determined for each individual. In each of the remaining three (treatment) sessions, nadolol (40 mg), bisoprolol (5 mg) or placebo was ingested, and isoprenaline hydrochloride (3.33-1000 ng min(-1)) was infused locally into the dorsal hand vein along with a constant dose of phenylephrine hydrochloride (to preconstrict the vein) 2 h after the ingestion of the drugs. Changes in vein diameter were monitored with the dorsal hand vein compliance technique. Subjects were allocated to treatment session according to a double-blind balanced cross-over design. Systolic and diastolic blood pressure, and heart rate were also measured.

RESULTS

Isoprenaline produced dose-dependent venodilatation which was antagonized by nadolol but remained unaffected by bisoprolol (ANOVA with repeated measures: P < 0.025; Dunnett's test: placebo vs nadolol, P < 0.01; placebo vs bisoprolol, P = NS). Mean log ED50 (ng min-1) was significantly increased in the presence of nadolol and remained unchanged in the presence of bisoprolol (ANOVA, P < 0.025; Dunnett's test: placebo vs nadolol, P < 0.005; placebo vs bisoprolol, P = NS; differences between mean log ED50 [95% CI]: placebo vs bisoprolol -0.11 [-0.38, 0.16], placebo vs nadolol 0.32[0.09, 0.72], bisoprolol vs nadolol -0.43 [-0.71, -0.15]). Mean Emax did not differ in the three treatment conditions.

CONCLUSIONS

The failure of bisoprolol to attenuate isoprenaline-evoked venodilatation in the human dorsal hand vein argues against the involvement of a beta1-adrenoceptor-mediated component in the isoprenaline-evoked venodilatory responses. The possibility cannot be excluded that the consequences of beta1-adrenoceptor blockade by bisoprolol might have been obscured by a possible venodilator effect of bisoprolol.

Comparison of the effects of venlafaxine, desipramine, and paroxetine on noradrenaline- and methoxamine-evoked constriction of the dorsal hand vein

AIMS

To examine whether the antidepressant venlafaxine, a novel serotonin-noradrenaline re-uptake inhibitor (SNRI), can modify alpha-adrenoceptor-mediated venoconstriction in man. The effects of venlafaxine were compared with those of desipramine, a tricyclic antidepressant with noradrenaline uptake inhibiting properties, and paroxetine, a selective serotonin re-uptake inhibitor (SSRI), on noradrenaline-and methoxamine-evoked venoconstriction using the dorsal hand vein compliance technique.

METHODS

Fifteen healthy male volunteers participated in five weekly experimental sessions. Each session was associated with a clinically effective dose of an antidepressant or placebo. The following oral dosages were used: venlafaxine 75 mg, venlafaxine 150 mg, desipramine 100 mg, paroxetine 20 mg, or placebo. A double-blind, cross-over, balanced design was used. In each session, dose-response curves to both locally infused noradrenaline acid tartrate (0.1-33.33 ng min-1 ) and methoxamine hydrochloride (0.5-121.5 microg min-1 ) were constructed. Systolic and diastolic blood pressure and pulse rate were measured in the supine and erect positions. Salivation was measured by the dental roll technique.

RESULTS

Venlafaxine 150 mg and desipramine 100 mg potentiated the venoconstrictor response to noradrenaline (anova of log ED50s: P<0.01; individual comparisons: venlafaxine 150 mg vs placebo: P<0.005; mean difference, 95% CI: -0. 49 (-0.81, -0.17); desipramine 100 mg vs placebo: P<0.005; mean difference, 95% CI: -0.34 (-0.60, -0.09) without affecting the response to methoxamine. Neither paroxetine nor placebo had any effects on the venoconstrictor responses. Both doses of venlafaxine increased systolic blood pressure (supine and erect) and venlafaxine 150 mg increased diastolic blood pressure (supine) (anova, P<0.05). Desipramine increased heart rate (P<0.05). Desipramine and both doses of venlafaxine reduced salivation (P<0.025).

CONCLUSIONS

These results show that, similarly to desipramine 100 mg, venlafaxine 150 mg can potentiate venoconstrictor responses to noradrenaline, consistent with venlafaxine's ability to block noradrenaline uptake in man. The importance of noradrenaline uptake blockade in these observations is confirmed by the lack of effect of the antidepressants on methoxamine-evoked venoconstriction and the failure of paroxetine to modify noradrenaline-evoked venoconstriction.

Comparison of the effects of nadolol and bisoprolol on noradrenaline-evoked venoconstriction in man in vivo

AIMS

In an attempt to explore the possible involvement of venodilator beta-adrenoceptors in the constrictor response of the human dorsal hand vein to noradrenaline, we examined the ability of nadolol, a non-selective beta1/beta2-adrenoceptor antagonist, and bisoprolol a selective beta1-adrenoceptor antagonist, to potentiate the response.

METHODS

Twelve healthy male volunteers participated in three weekly sessions. In each session nadolol (40 mg), bisoprolol (5 mg) or placebo was ingested, and (-) noradrenaline acid tartrate (0.33-33.33 ng min ) was infused locally into the dorsal hand vein 2 h after the ingestion of the drugs. Changes in vein diameter were monitored with the dorsal hand vein compliance technique. Subjects were allocated to treatments and sessions according to a double-blind balanced cross-over design. Systolic and diastolic blood pressure, and heart rate were also measured.

RESULTS

Noradrenaline produced dose-dependent venoconstriction which was antagonized by bisoprolol but remained unaffected by nadolol (ANOVA with repeated measures: F(2,22) = 5.07, P < 0.025; Dunnett's test: placebo vs nadolol; t = 0.35, df = 22, k = 3, NS; placebo vs bisoprolol; t = 2.83, df = 22, k = 3, P < 0.01). Mean (+/- s.e. mean) logED50s (ng min[-1]) were 0.44 +/- 0.15 (placebo), 0.73 +/- 0.11 (bisoprolol) and 0.50 +/- 0.21 (nadolol); mean (95% CI) differences were 0.29 (-0.005, 0.58) for placebo vs bisoprolol and 0.06 (-0.35, 0.46) for placebo vs nadolol. Both active drugs significantly (compared with placebo, P < 0.05) decreased (mean change from pretreatment +/- s.e. mean) heart rate (bisoprolol -16.08 +/- 2.01; nadolol -11.67 +/- 2.06) and systolic blood pressure (bisoprolol -15.0 +/- 0.80; nadolol -9.47 +/- 0.18).

CONCLUSIONS

The failure of nadolol and bisoprolol to potentiate noradrenaline-evoked venoconstriction argues against the involvement of masked venodilator beta-adrenoceptors in the response. The mechanism underlying the antagonism of noradrenaline-evoked venoconstriction by bisoprolol remains to be elucidated.

Bisoprolol attenuates noradrenaline- and phenylephrine-evoked venoconstriction in man in vivo

AIMS

The aim of this study was to examine the effects of bisoprolol (BIS), a selective beta1-adrenoceptor antagonist without partial agonistic activity, on noradrenaline- and phenylephrine-evoked venoconstriction in man using the dorsal hand vein compliance technique.

METHODS

Twelve healthy male volunteers participated in three weekly experimental sessions. Subjects were allocated to treatments and sessions on a double-blind basis. In each session either BIS 5 mg (BIS5), or BIS 10 mg (BIS10), or placebo was administered orally, and noradrenaline acid tartrate (0.1-33.33 ng min (-1) followed by phenylephrine hydrochloride (0.033-10 microg min(-l)) was infused into the dorsal hand vein. Systolic and diastolic blood pressure and heart rate were also measured.

RESULTS

Both noradrenaline and phenylephrine produced dose-dependent venoconstriction: the geometric mean ED50 for noradrenaline was 3.21 ng min(-1) and for phenylephrine 135.04 ng min(-1); the potency ratio (noradrenaline/phenylephrine) was 42. Both BIS5 and BIS10 significantly decreased the venoconstriction to noradrenaline (ANOVA; P<0.005), and to phenylephrine (ANOVA; P<0.001). The antagonism of the venoconstrictor responses was also reflected in a significant increase in logED50 values for both noradrenaline (ANOVA; P<0.005), and phenylephrine (ANOVA; P<0.0025) in the presence of both doses of BIS. Both doses of BIS significantly decreased heart rate (ANOVA; P<0.0001), and systolic blood pressure (ANOVA; P<0.0025).

CONCLUSIONS

Bisoprolol can antagonize alpha1-adrenoceptor mediated venoconstriction in the human dorsal hand vein in vivo through a mechanism which remains to be elucidated.