Distribution of input and output synapses on the central branches of bushcricket and cricket auditory afferent neurones: Immunocytochemical evidence for GABA and glutamate in different populations of presynaptic boutons
M. Hardt et Ahd. Watson, Distribution of input and output synapses on the central branches of bushcricket and cricket auditory afferent neurones: Immunocytochemical evidence for GABA and glutamate in different populations of presynaptic boutons, J COMP NEUR, 403(3), 1999, pp. 281-294
In order to investigate the synapses on the terminals of primary auditory a
fferents in the bushcricket and cricket, these were impaled with microelect
rodes and after physiological characterisation, injected intracellularly wi
th horseradish peroxidase. The tissue was prepared for electron microscopy,
and immunocytochemistry for gamma-aminobutyric acid (GABA) and glutamate w
as carried out an ultrathin sections by using a post-embedding immunogold t
echnique. The afferent terminals received many input synapses. Between 60-6
5% of these were made by processes immunoreactive for GABA and approximatel
y 25% from processes immunoreactive for glutamate. The relative distributio
n of the different classes of input were analysed fi om serial section reco
nstruction of terminal afferent branches. Inputs from GABA and glutamate-im
munoreactive processes appeared to be scattered at random over the terminal
arborisation of the afferents both with respect to each other and to the a
rchitecture of the terminals. They were, however, always found close to the
output synapses. The possible roles of presynaptic inhibition in the audit
ory afferents is discussed in the context of the auditory responses of the
animals. J. Comp. Neurol. 403:281-294, 1999. (C) 1999 Wiley-Liss, Inc.