Ontogenesis of 5-hydroxytryptamine-like immunoreactive cells and their relationship with bombesin in chicken proventriculus.

By using a double-stain immunohistochemical procedure, the Aa. studied the onset, the behaviour and the possible interrelationship between the 5-HT-like and bombesin-like immunoreactive cells during the ontogenesis of chicken proventriculus and in adult animals. The 5-HT-like immunoreactive cells become evident from the 8th day of incubation and they reach their peak around the 16th day, then markedly decrease at hatching. In adult animal these cells are always present, but are not so numerous. Between the 14th and the 18th day many double-stained cells scattered among other only 5-HT or bombesin-like immunoreactive cells are present. They can also be observed in adults, but only occasionally.