Central inhibitory microcircuits controlling spike propagation into sensory terminals.
J. Comp. Neurol.. 2005-01-01; 484(2): 234-248
DOI: 10.1002/cne.20474
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1. J Comp Neurol. 2005 Apr 4;484(2):234-48.
Central inhibitory microcircuits controlling spike propagation into sensory
terminals.
Watson A(1), Le Bon-Jego M, Cattaert D.
Author information:
(1)School of Biosciences, Cardiff University, Cardiff CF10 3US, United Kingdom.
The phenomenon of afferent presynaptic inhibition has been intensively studied in
the sensory neurons of the chordotonal organ from the coxobasal joint (CBCO) of
the crayfish leg. This has revealed that it has a number of discrete roles in
these afferents, mediated by distinct populations of interneurons. Here we
examine further the effect of presynaptic inhibition on action potentials in the
CBCO afferents and investigate the nature of the synapses that mediate it. In the
presence of picrotoxin, the action potential amplitude is increased and its
half-width decreased, and a late depolarizing potential following the spike is
increased in amplitude. Ultrastructural examination of the afferent terminals
reveals that synaptic contacts on terminal branches are particularly abundant in
the neuropil close to the main axon. Many of the presynaptic terminals contain
small agranular vesicles, are of large diameter, and are immunoreactive for
gamma-aminobutyric acid (GABA). These terminals are sometimes seen to make
reciprocal connections with the afferents. Synaptic contacts from processes
immunoreactive for glutamate are found on small-diameter afferent terminals. A
few of the presynaptic processes contain numerous large granular vesicles and are
immunoreactive for neither GABA nor glutamate. The effect that the observed
reciprocal synapses might have was investigated by using a multicompartmental
model of the afferent terminal.
Copyright 2005 Wiley-Liss, Inc.
DOI: 10.1002/cne.20474
PMID: 15736226 [Indexed for MEDLINE]