Evidence for a mesolimbic pathway in anuran amphibians: a combined tract-tracing/immunohistochemical study

The aim of the present study was to determine whether a dopaminergic mesolimbic pathway, as found in the brain of amniotes, also exists in anuran amphibians. For that purpose, application of retrograde tracers in the nucleus accumbens of Rana perezi was combined with tyrosine hydroxylase immunohistochemistry. Double labeled cells were found in the dorsomedial part of the posterior tubercle and, more frequently, in the midbrain tegmentum. It may be concluded, therefore, that a dopaminergic mesolimbic pathway does exist in amphibians. Nevertheless, the organization of the ventral (mesolimbic) and dorsal parts of the mesostriatal connections seems to vary from a caudal-to-rostral arrangement in amphibians to a medial-to-lateral arrangement in amniotes.