Distribution Of GABA And 5-HT Immunoreactive Neurons In The Protocerebrum And Deutocerebrum Of Butterfly Mimathyma Schrenckii

The distribution of γ -aminobutyric acid (GABA) and serotonin (5-HT) immunoreactive neurons in the protocerebrum and deutocerebrum of the butterfly Minathyma schrenckii were studied with the Colophony-paraffin (CP) embedding serial section technique and the Streptavidin-peroxidase (SP) immunohistochemical method. About 3 900 neurons per brain hemisphere exhibit GABA-immunoreactivity. Most of these are clustered into 14 groups and are located near the neuropils of medulla (group M1-3), lobula complex (group LC1-3), mushroom body (group PM1-3), central body complex (group PM4-5), antennal lobe (group AL1-2), and dorsal lobe (group D). Processes from GABA-like neurons supply all neuropils of the whole brain, which exhibit GABA immunoreactivity to a very different degree, and the lower division of central body together with the lateral accessory lobe is the most prominent immunoreactive area. However, in each brain hemisphere, there are only 62 5-HT positive neurons, which are scattered around the neuropils of the mid-brain. In addition, some special 5-HT nucleus-immunoreactive neurons are detected in the superior medial protocerebrum and inner cell groups of deutocerebrum besides the classical 5-HT-like immunoreactive neurons (being labeled only in cytoplasm or whole somata). All major neuropil regions are labeled by 5-HT antiserum except the optic lobes, antennal lobes and calyces of mushroom bodies, which are almost devoid of 5-HT immunoreactivity. Moreover, certain photoreceptors in the compound eyes of this taxon react with GABA and 5-HT antiserum. In general, GABA-like immunoreactive neurons densely exist in the brain and always gather into groups. It is more important in mediating local neural interactions. While the somata of 5-HT-like immunoreactivie neurons locate dispersedly. 5-HT might play roles in mediating distant neural interactions. These two neurotransmitters, GABA and 5-HT, might cooperate in some specific areas. The results and analyses offered academic foundation to the research concerning visual physiological mechanism and accumulated scientific information for the development of neurobiology.