Synaptic inhibition of the M-current: slow excitatory post-synaptic potential mechanism in bullfrog sympathetic neurones.
1. Slow muscarinic excitatory post-synaptic currents (slow e.p.s.c.s) generated by preganglionic nerve stimuli were recorded in voltage-clamped bullfrog sympathetic neurones. 2. IM--an outward, voltage-dependent, K+-current--was inhibited during the slow e.p.s.c., and membrane conductance was reduced in a voltage-dependent manner. 3. The slow e.p.s.c. was associated with reduced outward rectification in the steady-state current--voltage (I/V) curve at membrane potentials more positive than--60 m V, with no change in the shape of the non-rectifying part of the I/V curve at more negative potential. 4. The amplitude of the slow e.p.s.c. was reduced by membrane hyperpolarization, to zero at membrane potentials equal to, or more negative than, -60 m V. The voltage sensitivity of the slow e.p.s.c. accorded with that of IM. 5. It is concluded that the slow e.p.s.c. results from a selective inhibition of IM.
D000200:Action Potentials; D000818:Animals; D001339:Autonomic Fibers, Preganglionic / Q000502:physiology*; D004553:Electric Conductivity; D005728:Ganglia, Sympathetic / Q000502:physiology*; D066298:In Vitro Techniques; D008564:Membrane Potentials; D011188:Potassium / Q000502:physiology; D011892:Rana catesbeiana; D013569:Synapses / Q000502:physiology
D011188:Potassium