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An immunohistochemical study was conducted on the ontogeny of pituitary adenylate cyclase-activating polypeptide-27 (PACAP) immunoreactive elements within the extrinsic and intrinsic nerve supply of the chicken embryo gut. The first PACAP-immunoreactivity was detected in the extrinsic nerve supply at E 4 within the pharyngeal region and the primary sympathetic chain. At E 5.5 it appeared in the vagus nerve, the spinal cord, the secondary sympathetic chain, some perivascular plexuses and the Remak ganglion. In the intrinsic nerve supply, the first PACAP-immunoreactive elements were shown at E 4.5-E 5 in the mesenchymal bud of the proventriculus/gizzard. Then they gradually appeared also cranially and caudally both in myenteric and submucous plexuses.

A new amphibian peptide family has been isolated from the skin of a South American frog Phyllomedusa rhodei and named Tryptophyllins (TPH) because of their content in tryptophyl residue. Using an antiserum against one of these peptides, namely the pentapeptide Met-5-TPH-5-amide (PHE-PRO-PRO-TRP-MET-NH2), we observed the presence of a set of immunoreactive cells in rat adenohypophysis. These cells were far more numerous in pregnant than in normal male and non-pregnant female rats. Dual immunostainings demonstrated that, with some exceptions, almost all the TPH-like immunoreactive cells were gonadotrophs. At electron microscope both types of gonadotroph cells displayed immunoreactivity and the gold particles strongly labelled both types of granules. The Aa. advance the hypothesis that, besides the hormones themselves, the secretory granules might contain some TPH-like sequence.