α-Adrenergic receptor-mediated depolarization of rat neocortical astrocytes in primary culture

The membrane potentials of rat neocortical astrocytes growing in primary cultures (mean resting potential; −79 mV at [K⁺]_o = 4.5 nM) were depolarized by up to 30 mV by 10⁻⁵ M norepinephrine added to the medium, or up to 11 mV by norepinephrine or phenylephrine applied by ionophoresis. This depolarization could be inhibited by the α-adrenergic receptor antagonist phentolamine (10⁻⁵ M) but not by the β-adrenergic antagonist propranolol (10⁻⁵ M). These results suggest that the norepinephrine-evoked depolarizations seen in these cells may be mediated through an α-adrenergic receptor.