Neurons projecting to the retrocerebral complex of the adult blow fly, Protophormia terraenovae

Anatomical study of neurons projecting to the retrocerebral complex of the adult blow fly, Protophormia terraenovae, was done by NiCl2 filling and imm unocytochemistry. Retrograde filling through the cardiac-recurrent nerve la beled three groups of neurons in the brain/subesophageal ganglion: (1) para medial clusters of the pars intercerebralis, (2) neurons in each pars later alis, and (3) neurons in the subesophageal ganglion, The pars intercerebral is neurons send prominent axone into the median bundle and exit from the br ain via the contralateral nervus corporis cardiaci. Based on the projection pattern, two types of the pars lateralis neurons can be distinguished: the most lateral pairs of neurons contralaterally extend through the posterior lateral tract and the remainder ipsilaterally extend through the posterior lateral tract. The neurons in the subesophageal ganglion run through the c ontralateral nervus corporis cardiaci. The dendritic arborization of the pa rs intercerebralis and pars lateralis neurons is restricted to the superior protocerebral neuropil and to the anterior neuropil of the subesophageal g anglion where the neurons in the subesophageal ganglion also project. Retro grade filling from the corpus allatum indicated that the pars lateralis neu rons and a few pars intercerebralis neurons project to the corpus allatum, but that the neurons in the subesophageal ganglion do not. Orthograde filli ng from the pars intercerebralis and staining by paraldehyde-thionin/parald ehyde-fuchsin indicated that the pars intercerebralis neurons project prima rily to the corpus cardiacum/hypocerebral ganglion complex. Immunostaining with a polyclonal antiserum against diapause hormone, a member of the FXPRL amide family, suggests that some of the subesophageal ganglion neurons cont ain FXPRLamide-like peptides.