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.