OCTOPAMINE-LIKE IMMUNOREACTIVE NEURONS IN LOCUST GENITAL ABDOMINAL GANGLIA

Using a well characterized anti-serum, the distribution of octopamine- like immunoreactive neurones is described in the locust seventh abdomi nal (A7) and terminal ganglia (TG), which are associated with genital organs. Apart from 4 paired ventral somata occasionally observed in th e TG, all labelled cells could be identified as efferent dorsal- and v entral unpaired median (DUM/ VUM) neurones by virtue of the characteri stic large size and position of their somata, projections of their pri mary neurites in DUM-cell tracts, and bifurcating axons which arise fr om dorsal T-junctions and enter peripheral nerves. For the examined ga nglia our data indicate that the whole population of efferent DUM and VUM-cells, defined here as progeny of the segment specific unpaired me dian neuroblast with peripheral axons, are octopaminergic, and that eq ual numbers of these cells occur in both sexes: 8 in A7 and 11 in TG. Sex-specific differences are probably restricted to the axonal project ions of 5 octopamine-like immunoreactive DUM-somata in A7, and 5 in TG , which in females project into their segment specific sternal nerves, but in males into the genital nerve of the TG. Numerous intersegmenta lly projecting octopamine-like immunoreactive fibres traverse both gan glia. The majority probably stem from previously described octopamine- like immunoreactive neurones in the thoracic and suboesophageal gangli a.