The Muscarinic Receptor-Induced Action Potential Threshold Long-Term Plasticity Is Axon Dependent
(Ai, Bi, Ci, Di, and Ei) Representative traces under control conditions, after either global or local application of Oxo-M (1 μM) or stimulation of cholinergic fibers targeting distal granule cell (GC) axons and following 25 min Oxo-M washout or post-stimulation in intact axon (long axon [LA]) neurons or axonless neurons. The RMP is indicated adjacent to the traces. The inset shows the first trace segment on an expanded timescale. The average action potential number (AP No.) under the different conditions is shown on the right. The scales apply to all traces within the panels.
(Aii, Bii, Cii, Dii, and Eii) Typical single action potentials and phase plane plots under control conditions (black), after Oxo-M application or cholinergic fiber stimulation (red) and 25 min following Oxo-M washout or termination of the stimulation paradigm (blue).
(Fi) The mean spike threshold before, during, and 25 min after either Oxo-M treatment or cholinergic afferent stimulation.
(Fii) The threshold change time course during Oxo-M treatment and following washout of Oxo-M.
(Gi) Example electron micrographs showing immunoreactivity for muscarinic M1 receptor subunit. ax, axon; den, dendrites; AIS, axon initial segment. Scale bars, 0.2 μm.
(Gii) Quantification of gold particles labeling M1 receptor subunits in dentate gyrus. The numbers of observations are in parenthesis. n.s., nonsignificant.