Catecholamine systems in the brain of vertebrates: new perspectives through a comparative approach

A comparative analysis of catecholaminergic systems in the brain and spinal cord of vertebrates forces to reconsider several aspects of the organizati on of catecholamine systems. Evidence has been provided for the existence o f extensive, putatively catecholaminergic cell groups in the spinal cord, t he pretectum, the habenular region, and cortical and subcortical telencepha lic areas, Moreover, putatively dopamine- and noradrenaline-accumulating ce lls have been demonstrated in the hypothalamic periventricular organ of alm ost every non-mammalian vertebrate studied. In contrast with the classical idea that the evolution of catecholamine systems is marked by an increase i n complexity going from anamniotes to amniotes, it is now evident that the brains of anamniotes contain catecholaminergic cell groups, of which the co unterparts in amniotes have lost the capacity to produce catecholamines. Mo reover, a segmental approach in studying the organization of catecholaminer gic systems is advocated. Such an approach has recently led to the conclusi on that the chemoarchitecture and connections of the basal ganglia of anamn iote and amniote tetrapods are largely comparable. This review has also bro ught together data about the distribution of receptors and catecholaminergi c fibers as well as data about developmental aspects. From these data it ha s become clear that there is a good match between catecholaminergic fibers and receptors, but, at many places, volume transmission seems to play an im portant role. Finally, although the available data are still limited, strik ing differences are observed in the spatiotemporal sequence of appearance o f catecholaminergic cell groups, in particular those in the retina and olfa ctory bulb. (C) 2000 Elsevier Science B.V. All rights reserved.