Noradrenaline receptors on the rat basilar artery.

1. Intracellular recordings were obtained from the arterial smooth muscle cells of rat basilar artery during perivascular nerve stimulation and during the application of adrenoceptor agonists and antagonists. 2. Perivascular nerve stimulation evoked excitatory junction potentials. Increased stimulation resulted in action potentials which were associated with arterial constriction. 3. Bath-applied noradrenaline did not cause constriction but at high concentrations caused membrane depolarization. The depolarization caused by a given dose of noradrenaline was larger in the presence of cocaine. 4. Neither the depolarizations obtained by nerve stimulation nor those obtained by bath-applied noradrenaline were blocked by adrenoceptor blocking agents. 5. Unlike alpha-receptors, the receptors on the rat basilar artery were activated equally well by dopamine, adrenaline, and both optical isomers of noradrenaline. 6. Excitatory junction potentials could be obtained in the presence of high bath concentrations of noradrenaline.