Chemical architecture of antennal pathways mediating proboscis extension learning in the honeybee

Abstract - The chief neuropiles mediating proboscis extension in response to antennal sugar water stimulation and also associative learning of an odour are the antennal lobes, the mushroom bodies, lateral parts of the protocerebrum, and the suboesophageal ganglion. This review focusses on the distribution of some classical neurotransmitters within olfactory pathways based on methods of chemical neuroanatomy. Chemosensory information processing and motor circuits for proboscis extension seem to include cholinergic projection and local interneurons, GABAergic interneurons, glutamatergic motoneurons, and aminergic neurons which link with extensive arborisations the neuromeres of the nervous system. Electrophysiological stimulation experiments and immunocytochemical investigations implicate octopaminergic ventral median neurons of the suboesophageal ganglion as a rewarding system in proboscis extension learning.