| Summary: | Activation of muscarinic acetylcholine receptors (mAChRs) has pronounced effects on GABAergic interneurons, including depolarization of their resting membrane potential, and increasing their action potential and vesicular release frequency. Moreover, postsynaptic mAChR activation in hippocampal pyramidal neurons reduces the expression of the K+-Cl- cotransporter (KCC2). However, whether mAChR activation modulates the expression of disinhibition-mediated synaptic plasticity has not been examined.
I induced inhibitory long-term potentiation (LTP) by applying coincident pre/postsynaptic stimulation in the hippocampus. This plasticity was characterized by an increase in the postsynaptic potential (PSP) amplitude and a depolarization in the inhibitory postsynaptic potential (IPSP) reversal potential; characteristics of disinhibition-mediated LTP (dmLTP). Activation of mAChRs during this plasticity induction protocol prevented the expression of dmLTP via a presynaptic downregulation of transmitter release. This was concluded from evidence that the PSP amplitude and IPSP reversal potential were unaltered, and paired-pulse depression occurred following plasticity induction in the presence of mAChR activation.
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