D. Cattaert et D. Le Ray, Direct glutamate-mediated presynaptic inhibition of sensory afferents by the postsynaptic motor neurons, EUR J NEURO, 10(12), 1998, pp. 3737-3746
An in vitro preparation of the crayfish central nervous system was used to
study a negative feedback control exerted by the glutamatergic motor neuron
s (MNs) on to their presynaptic cholinergic sensory afferents. This negativ
e control consists in small amplitude, slowly developing depolarizations of
the primary afferents (sdPADs) strictly timed with MN bursts. They were no
t blocked by picrotoxin, but were sensitive to glutamate non-N-methyl-D-asp
artate (NMDA) antagonists. Intracellular recordings were performed within t
hin branches of sensory terminals while electrical antidromic stimulation w
ere applied to the motor nerves, or while glutamate (the MN neurotransmitte
r) was pressure-applied close to the recording site. Electrical motor nerve
stimulations and glutamate pressure application had similar effects on to
sensory terminals issued from the coxo-basipodite chordotonal organ (CBTs):
like sdPADs, both stimulation-induced depolarizations were picrotoxin-resi
stant and were dramatically reduced by non-NMDA antagonist bath application
. These results indicate that sdPADs are likely directly produced by MNs du
ring locomotor activity. A functional scheme is proposed.