The triple co-localisation of peptidergic material immunoreactive to
antisera raised against allatostatins of the Y/FXFGL-NH2 type,
Manduca sexta allatostatin (Mas-AS), and
allatotropin has been demonstrated in a single pair of anterodorsal neurones in the frontal
ganglion of the tomato moth, Lacanobia oleracea (Noctuidae). Another pair of posterior neurones contain only Y/FXFGL-NH2-type
allatostatin immunoreactivity. The neurites of all four cells trifurcate, and axons project to the brain in the frontal connectives and to the foregut in the recurrent nerve. Axons from the anterior neurones, within the recurrent nerve, have prominent lateral branches supplying muscles of the crop, and axons from both anterior and posterior cells show profuse branching and terminal arborisations in the region of the stomodeal valve. The brain contributes Y/FXFGL-NH2-immunoreactive material, but not
allatotropin or Mas-AS, to the recurrent nerve via NCC 1+2 and NCC 3. All three
peptides have a reversible effect on the spontaneous (peristaltic) contractions of the foregut (crop) in vitro. Thus, both types of
allatostatin are inhibitory
at 10(-12) to 10(-7) M, whereas
allatotropin is strongly myostimulatory
at 10(-14) M. This is the first demonstration of the gut myoinhibitory effects of Mas-AS and, taken together with the effects of Y/FXFGL-NH2-type allatostatins and
allatotropin, reveals a different functional aspect to that normally attributed to these three
peptides, i.e. control of
juvenile hormone synthesis by the corpus allatum.