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Figure 4. Motoneuronal control of sensory synapses. (A) Paired intracellular recordings from a CBCO
sensory terminal and a depressor motoneuron. (B) Postsynaptic induction of LTP at a sensory-motor
synapse. (C) Cellular mechanisms of LTP induction. (D) Typical intracellular resistance reflex response
to CBCO mechanical stimulation (mvt). During the course of the recording, the Dep MN spontane-
ously depolarized from -65 mV to -55 mV (dashed lines), and the reflex response increased in amplitude
whereas the sensory firing frequency did not change. (E) Functional role of the muscarinic component
of the sensory-motor EPSPs. 1. At rest, the central drive to motoneurons is weak (thin line), as is the ef-
ficacy of the reflex loop (thin arrow). The cholinergic proprioceptive feedback involves mainly nicotinic
receptors (n). 2. When the CPG strongly excites motoneurons (thick line), muscarinic receptors (m) are
recruited and considerably enhance sensory-motor transmission to maintain it proportional to the cen-
tral drive. (F) Intracellular recording of slowly-developing primary afferent depolarizations (sdPADs)
from a CBCO terminal during strong locomotor bursts. (G) Cellular mechanisms of sdPADs-mediated
presynaptic inhibition.
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