Studies on the mechanisms of central action of alpha-adrenergic receptor blocking agents

The article summarizes the results of experiments, partly published, on the central action of alpha-adrenergic receptor blocking drugs given systemically in rats. Phenoxybenzamine, phentolamine and aceperone increase utilization of noradrenaline (NA in whole brain and antagonise NA--stimulated formation of cyclic AMP in brain cortical slices. They also counteracts locomotor hyperactivity and flexor reflex stimulation induced by NA receptor agonists. The investigated alpha-adrenolytics do not antagonize brain dopamine (DA) or acetycholine (ACh) receptor stimulation, although they weakly reduce the effects of central serotonin (5-HT) system activation. It is concluded, that phenoxybenzamine, phentolamine and aceperone block directly central NA receptors. They do not block DA or ACh receptors in the brain but they are weak antagonists of 5-HT system stimulation. The investigated compounds decelerate utilization of DA and increase those of ACh in the brain, these effects seem to be secondary to NA system hypofunction.