Three selective α(2A)- or α(2B)-adrenergic antagonists (BRL-44408, BRL-41992 and imiloxan) were used in the present study designed to classify the presynaptic α2-auto- and heteroreceptors in the rat brain cortex. The rank order of potency in antagonizing the inhibitory effect of (-)-noradrenaline or clonidine on the K+-induced [3H]noradrenaline and [3H]5-hydroxytryptamine (5-HT) release from superfused synaptosomes was BRL-44408 ≥ BRL-41992 >> imiloxan. The same rank order was found for the affinities of these compounds for [3H]yohimbine binding in human platelet membranes, containing only α(2A)-adrenoceptors, but does not correlate with the known affinities for α(2B)-adrenoceptors (BRL-41992 ≥ imiloxan > BRL-44408). These data support the conclusion that presynaptic α2-auto- and heteroreceptors in rat brain cortex do not belong to the α(2B)-subtype and suggest that the modulation of noradrenaline and 5-HT release may be mediated by the α(2A)-subtype.
|Number of pages||4|
|Journal||Journal of Pharmacy and Pharmacology|
|Publication status||Published - 1993|
ASJC Scopus subject areas
- Pharmaceutical Science