Characterization of the proctolinergic and GABAergic systems in the terminal ganglion of the male and female cockroach, Periplaneta americana, and effects of insecticide treatment. Immunohistochemistry and computer-assisted image analysis.
The distribution of proctolin- and gamma-aminobutyric acid (GABA)-containing neurons in males and females of the American cockroach, Periplaneta americana, was evaluated by means of immunohistochemistry. Sex-related differences in the localization of proctolinergic cells are restricted to the median region of the terminal ganglion. No coexistence was found for GABA and proctolin. The high specificity of the GABA staining was confirmed by labelling of identical neurons with both anti-GABA and anti-glutamic acid decarboxylase (GAD) antisera. The volume fractions occupied by GABA- and proctolin-immunoreactive elements were evaluated using a computer-based method of planimetric area percentage. The GAD staining was markedly decreased after carbaryl insecticide treatment and the volume fraction of proctolin-immunoreactive neurons was significantly reduced after application of another insecticide, dieldrin.