DISTRIBUTION OF SYNAPSES ON 2 ASCENDING INTERNEURONS CARRYING FREQUENCY-SPECIFIC INFORMATION IN THE AUDITORY-SYSTEM OF THE CRICKET - EVIDENCE FOR GABAERGIC INPUTS
M. Hardt et Ahd. Watson, DISTRIBUTION OF SYNAPSES ON 2 ASCENDING INTERNEURONS CARRYING FREQUENCY-SPECIFIC INFORMATION IN THE AUDITORY-SYSTEM OF THE CRICKET - EVIDENCE FOR GABAERGIC INPUTS, Journal of comparative neurology, 345(4), 1994, pp. 481-495
Two identified cricket auditory interneurones, AN1 and AN2, were intra
cellularly labelled with horseradish peroxidase following physiologica
l characterisation. The neurones, which have some structural similarit
ies, have their somata in the prothoracic ganglion and axons that proj
ect to the brain. Although both carry auditory information, they have
different response properties and participate in different types of ph
onotactic behaviour. Ultrathin sections from selected regions of their
prothoracic arborisations were examined in the electron microscope af
ter postembedding immunostaining for the inhibitory transmitter GABA.
In the prothoracic ganglion AN1 branches only in the medial ventral as
sociation centre (mVAC) contralateral to the soma, and receives only i
nput synapses. Twenty-seven percent of these were made by processes im
munoreactive for GABA. AN2 branches not only in mVAC on both sides of
the ganglion but also in several other areas. It makes output synapses
from large diameter neurites in mVAC on both sides of the ganglion as
well as from neurites in more posterior regions of the neuropile. Mos
t input synapses are received onto branches in the contralateral mVAC
where about 19% were made from GABA-immunoreactive processes, (C) 1994
Wiley-Liss, Inc.