Ga. Kerchner et al., Direct presynaptic regulation of GABA/glycine release by kainate receptorsin the dorsal horn: An ionotropic mechanism, NEURON, 32(3), 2001, pp. 477-488
In the spinal cord dorsal horn, excitatory sensory fibers terminate adjacen
t to interneuron terminals. Here, we show that kainate (KA) receptor activa
tion triggered action potential-independent release of GABA and glycine fro
m dorsal horn interneurons. This release was transient, because KA receptor
s desensitized, and it required Na+ entry and Ca2+ channel activation. KA m
odulated evoked inhibitory transmission in a dose-dependent, biphasic manne
r, with suppression being more prominent. In recordings from isolated neuro
n pairs, this suppression required GABA(B) receptor activation, suggesting
that KA-triggered GABA release activated presynaptic GABA(B) autoreceptors.
Finally, glutamate released from sensory fibers caused a KA and GABA(B) re
ceptor-dependent suppression of inhibitory transmission in spinal slices. T
hus, we show how presynaptic KA receptors are linked to changes in GABA/gly
cine release and highlight a novel role for these receptors in regulating s
ensory transmission.