Interactions of the ring gland, ovaries, and juvenile hormone with brain neurosecretory cells in Musca domestica

Abstract

The staining intensity (median neurosecretory cell index) of the median neurosecretory cells (MNC) in Musca domestica increased as oögenesis progressed from stages 2 to 10. The amount of neurosecretory material within the MNC was dependent upon the presence of ovaries with developing or mature follicles. Ovariectomized flies had a median neurosecretory index that was 50 per cent less than that of control flies with mature eggs. In addition, we found that ring gland removal decreased the staining frequency of three different neurosecretory cell groups; increased staining frequency in another; increased the amount of neurosecretory material within the MNC fibre tract; increased the cytoplasmic area of types A and A′ MNC. Furthermore, neither the juvenile hormone analogue nor the ring gland had a direct effect on the median neurosecretory cell index but did influence neurosecretory activity indirectly by activating the ovaries. We hypothesize that an ovarian hormone—the oöstatic hormone—regulates either the release from or synthesis of neurosecretory material within the MNC.