Pharmacological comparison of isolated human cerebral and digital arteries.

Abstract

Some basic pharmacological differences between isolated human cerebral and digital arteries obtained at postmortem were studied. Spiral strip responses were measured isometrically and cumulative drug dose-response curves obtained. Contractile responses were sought to norepinephrine [NE], 5-hydroxytryptamine, angiotensin, histamine, KCl, BaCl2 and prostaglandin[PG]F2.alpha.. Relaxation responses (either by the agonists on their own, or in the presence of a resting tonus induced by KCl or 5-hydroxytryptamine) were sought to isoproterenol, histamine, acetylcholine and dopamine. There were no differences between the cerebral or digital arteries in the non-specific responses to KCl or BaCl2. Nor were there any differences in the responses to PGF2.alpha., or in the receptor-mediated responses to 5-hydroxytryptamine or angiotensin. This was in marked contrast to the responses produced by NE where the maximum response was much larger in digital arteries than in cerebral arteries, although there were no differences in the sensitivity of the 2 vessels to NE (as measured by the ED50 values). Relaxation responses were difficult to elicit and very variable with only occasional preparations showing relaxation to any of the agonists. The only major pharmacological difference between human digital and cerebral vessels is apparently the number, rather than the sensitivity, of the noradrenergic .alpha.-receptors.