Age-dependent neurosecretion release induced by dopamine in the corpora cardiaca of Blattella germanica (L.) (Dictyoptera : Blattellidae)

In addition to glial cells, intrinsic glandular cells and ordinary axons, the corpora cardiaca of Blattella germanica (L.) (Dictyoptera : Blattellidae) contain 4 types of neurosecretory fibers originating from the brain (types 1, 2, 3, and 4), which can be recognized on the basis of the size, form, and electron density of their neurosecretory granules. A comparative ultrastructural study of the corpora cardiaca from normal females and from dopamine-treated (1 μg) females has been carried out at different stages within the first ovarian cycle (freshly emerged: day 0; 2-day-old: pre-vitellogenesis; 4-day-old: beginning of vitellogenesis; 6-day-old: full vitellogenesis; 8-day-old: post-vitellogenesis, period of ootheca transport). Quantitative data on the exocytotic configurations observed in each type of fiber (1–4) have led to the following conclusions: (a) the exocytotic configurations in control specimens are too infrequent to prompt any inference about the dynamics of neurosecretion release in the different types of fibers; (b) dopamine treatment induces a stimulation of the exocytotis phenomenon, whose extent depends on the specimen age and on the type of fiber. Therefore, on days 2 and 6, dopamine: preferentially stimulates neurosecretion release in the fibers of types 3 and 4 respectively.