In the cockroach Diploptera punctata, sequencing of the
cDNA for the insect myoinhibitory
neuropeptide,
leucomyosuppressin (LMS), has demonstrated that LMS is the only
Phe-Met-Arg-Phe-amide (NH2) (
FMRFamide)-related
peptide to be encoded by this gene (Donly et al. [1996] Insect Biochem. Mol. Biol. 26:627-637). However, in the present study, high performance liquid chromatography analysis of brain extracts showed six discrete
FMRFamide-like immunoreactive fractions, one of which co-eluted with LMS. This study compared the distribution of
FMRFamide-related
peptides visualized by immunohistochemistry with LMS
mRNA expression demonstrated by in situ hybridization in D. punctata. Immunohistochemistry with a polyclonal antiserum generated against
FMRFamide, but which recognizes extended
RFamide peptides, demonstrated numerous
RFamide-like immunoreactive cells and processes in both nervous and nonnervous tissues.
RFamide-like immunoreactivity was found in cells and processes of the brain and optic lobes, the stomatogastric nervous system, including the frontal and ingluvial ganglia, and the suboesophageal
ganglion. Immunoreactivity was also present in all ganglia of the ventral nerve cord and in the alimentary canal. Within the alimentary canal, positively stained processes were found in the crop, midgut, and hindgut, and immunoreactive endocrinelike cells were located in the midgut. In situ hybridization with a
digoxigenin-labeled
RNA probe spanning the entire LMS coding region showed cell bodies containing LMS
mRNA in all ganglia studied, other than the ingluvial
ganglion. Expression was most abundant in the brain and optic lobes and in the frontal and suboesophageal ganglia. LMS
mRNA was also apparent, although less intensely, in all other ganglia of the ventral nerve cord. Within the alimentary canal, LMS
mRNA-positive cells were only visible in the anterior portion of the midgut, in the endocrinelike cells. The appearance of LMS
mRNA in the central nervous system, stomatogastric nervous system, and midgut suggests that LMS may play a central role in Diploptera and may be associated with feeding and digestion.