Fc. Rind et G. Leitinger, Immunocytochemical evidence that collision sensing neurons in the locust visual system contain acetylcholine, J COMP NEUR, 423(3), 2000, pp. 389-401
The lobula giant movement detector (LGMD1 and -2) neurons in the locust vis
ual system are parts of motion-sensitive pathways that detect objects appro
aching on a collision course. The dendritic processes of the LGMD1 and -2 i
n the lobula are localised to discrete regions, allowing the dendrites of e
ach neuron to be distinguished uniquely. As was described previously for th
e LGMD1, the afferent processes onto the LGMD2 synapse directly with each o
ther, and these synapses are immediately adjacent to their outputs onto the
LGMD2. Here we present immunocytochemical evidence, using antibodies again
st choline-protein conjugates and a polyclonal antiserum against choline ac
etyltransferase (ChAT; Chemicon Ab 143), that the LGMD1 and -2 and the reti
notopic units presynaptic to them contain acetylcholine (ACh). It is propos
ed that these retinotopic units excite the LGMD1 or -2 but inhibit each oth
er. It is well established that ACh has both excitatory and inhibitory effe
cts and may provide the substrate for a critical race in the LGMD1 or -2, b
etween excitation caused by edges moving out over successive photoreceptors
, and inhibition spreading laterally resulting in the selective response to
objects approaching on a collision course. In the optic lobe, ACh was also
found to be localised in discrete layers of the medulla and in the outer c
hiasm between the lamina and medulla. In the brain, the antennal lobes cont
ained neurons that reacted positively for ACh. Silver- or haematoxylin and
eosin-stained sections through the optic lobe confirmed the identities of t
he positively immunostained neurons. (C) 2000 Wiley-Liss, Inc.