Pharmacological evidence that somatostatin activates the m-current in hippocampal pyramidal neurons

In the in vitro hippocampal slice somatostatin has been shown to cause a direct hyperpolarization of CA 1 pyramidal neurons by increasing a potassium conductance which is resistant to blockade by tetraethylammonium 4-aminopyridine, or cesium ions. Results reported here demonstrate that this somatostatin-induced hyperpolarization is blocked by 1 mM barium and 5 x 10(-5) M carbachol, with the action of carbachol being reversed by atropine. Barium and carbachol both inactivate the m-current and these results suggest that somatostatin may exert its hyperpolarizing action on CA1 pyramidal cells by activation of the m-current.