Presence and coexistence of chromogranin A and multiple neuropeptides in Merkel cells of mammalian oral mucosa.

By the use of light microscopic (LM) immunohistochemistry, Merkel cells of the mammalian oral mucosa have been examined for the presence and coexistence of some neuropeptides and of the neuroendocrine marker chromogranin A (CG-A). Peptide and CG-A immunophenotypes of oral Merkel cells were found to vary between species and to depend on the developmental stage, as exemplarily revealed in the pig. Oral Merkel cells of adult cat, mouse and pig but not those of adult guinea pig stained for calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal polypeptide (VIP) and peptide histidine isoleucine (PHI).

Co-existence of prodynorphin--opioid peptides and substance P in primary sensory afferents of guinea-pigs.

Light microscopic immunoenzymatic and immunofluorescence histochemistry revealed co-existence of opioid peptides with substance P in primary sensory neurons of all segmental dorsal root and trigeminal ganglia of guinea-pig. Sensory opioid peptides appeared to be exclusively processed from prodynorphin and include [Leu]enkephalin, neoendorphins, and dynorphin A. We suggest the presence of presynaptic opioid autoreceptors in primary sensory afferences.