Abstract
A large number of papers has revealed the existence of catecholamines (CA) and 5-hydroxytryptamine (5-HT) in the central nervous system of mammals (1-5). These amines were extensively distributed in the brain, especially in the subcortical areas. Moreover, many investigators have made considerable contributions to studies on the distribution of CA and 5-HT in the central nervous system of vertebrates phylogenically below Mammal (6-13). Of them, Brodie, Bogdanski and Bonomi (7) reported the ratio of 5-HT to CA in the brain of all vertebrate classes. This ratio is about 1: 1 in the rat, whereas it is 2 or more in birds, reptiles and amphibians. Significant interplay of these monoamines concerning functions of the central nervous system might be conclusive, even though definite evidences have been awaiting.
Scandinavian group (14-16) has developed histo-chemical method for the detection of monoamines by using the emission of fluorescence from CA and 5-HT. This method made it possible to observe the cellular localization of monoamines not only in the peripheral organs but also in the central nervous system. In the central nervous system of mammals (mainly in rats), the distribution of CA and 5-HT in different nerve cells and in a variety of nerve terminals and fibers have been demonstrated (17-21). On the other hand, such investigations in the brain of vertebrates phylogenically below Mammal have been carried out only in the limited animal species and the limited region of the brain. As far as we know, there were such reports with regard to the upper brain stem of the pigeon (22), the median eminence of the chicken (23, 24), and the brain of fish (25). Therefore, the present study was undertaken to establish the topographical distribution of monoamine-containing cells in the central nervous system of the chicken and to observe their responses to various drugs interfering with the monoamine metabolism. The distribution of monoamine-containing terminals and fibers in the central nervous system of the chicken will be described in the coming paper.
