Modulation of action potential during the late slow excitatory postsynaptic potential in bullfrog sympathetic ganglia

The spike peak and after-hyperpolarization of the action potential of bullfrog sympathetic ganglion cells were depressed during the late slow excitatory postsynaptic potential (EPSP). These changes in the action potential were mimicked by luteinizing hormone-releasing hormone (LH-RH), a neurotransmitter candidate for the late slow EPSP. LH-RH (5 microM) suppressed the voltage-dependent K+ currents, both the delayed rectifier K+ current (IK1) and the M current (IK2). It is suggested that the depression of the after-hyperpolarization of the action potential during the late slow EPSP may be due to suppression of IK1 and IK2.