AFFERENT CONNECTIONS OF THE NUCLEUS-ACCUMBENS OF THE SNAKE, ELAPHE GUTTATA, STUDIED BY MEANS OF IN-VITRO AND IN-VIVO TRACING TECHNIQUES IN COMBINATION WITH TH IMMUNOHISTOCHEMISTRY

The aim of the present study was to determine the afferent connections of the nucleus accumbens in snakes, in particular its catecholaminerg ic input. For that purpose, in vitro and in vivo applications of retro grade tracers in the nucleus accumbens of Elaphe guttata were combined with tyrosine hydroxylase (TH) immunohistochemistry. Both techniques revealed telencephalic inputs to the nucleus accumbens originating fro m the diagonal band of Broca, ventral pallidum, amygdaloid complex, an d dorsal cortex. Major diencephalic inputs arise from the dorsomedial thalamic nucleus and the hypothalamus. In the brainstem, a few retrogr adely labeled cells were observed in the raphe nucleus and the locus c oeruleus. Considerably more cells were found in the midbrain tegmentum . Within the confines of the locus coeruleus and, in particular, the m idbrain tegmentum, retrogradely labeled cells stained also for TH sugg esting that those areas constitute the major catecholaminergic input t o the nucleus accumbens of snakes. The experimental approach used in t he present study, in particular the in vitro technique, seems to be ve ry suited for studying the development of basal ganglia organization o f reptiles in the near future. (C) 1997 Elsevier Science Ireland Ltd.