Immunocytochemical demonstration of proopiomelanocortin- and other opioid-related substances and a CRF-like peptide in the gut of the american cockroach, Periplaneta americana L.

Using the peroxidase-antiperoxidase technique, we showed the presence of peptides which are immunologically resembling mammalian corticotropin releasing hormone (CRF)-, adrenocorticotropic hormone (ACTH)-, beta-endorphin (beta-END)-, alpha-melanocyte stimulating hormone (alpha-MSH)-, methionine-enkephalin (met-ENK)- and leucine enkephalin (leu-ENK)- like immunoreactivity in hundreds to thousands of endocrine cells and nerve fibers in the midgut of the American cockroach Periplaneta americana. In the cockroach hindgut no immunoreactive cell bodies could be observed, although nerve fibers were clearly noticed to be recognized by antisera to CRF, ACTH1-24, ACTH11-24 and beta-END. Nothing is exactly known as to the function(s) of the demonstrated materials, but one can speculate that these numerous immunoreactive cells, might have important paracrine and/or endocrine functions in the insect physiology.