| Abstract: | Summary Slices of rat cerebral cortex were preincubated with 10–7 M (-)-3H-noradrenaline, and the outflow of tritium was determined. Oxymetazoline, phentolamine and cocaine did not change the spontaneous efflux. The overflow of tritium evoked by electrical field stimulation was decreased by oxymetazoline, and enhanced by phentolamine, phenoxybenzamine, and cocaine. Oxymetazoline did not counteract the increase of the stimulation-induced overflow caused by cocaine, but strongly antagonized the increase caused by phentolamine and phenoxybenzamine. When the stimulation-induced overflow was large under control conditions (high frequency of stimulation, addition of cocaine), the inhibitory effect of oxymetazoline was diminished. The results indicate that an  -receptor-mediated feed-back control of noradrenaline release, previously demonstrated in postganglionic sympathetic nerves, also operates in central noradrenergic neurones. |
