Evidence for a catecholaminergic projection to area X in the zebra finch

Abstract In the zebra finch (Poephila guttata) , horseradish peroxidase injected into or near Area X of the lobus parolfactorius (LPO) is transported to cell bodies in ipsilateral hyperstriatum ventrale pars caudale (HVc), area ventralis of Tsai (AVT), and nucleus tegmenti pedunculo‐pontinus, pars compacta (TPc). Area X, LPO, and paleostriatum augmentatum (PA) all contain a dense network of catecholamine‐containing axons and nerve terminals, as determined in histofluorescence studies. Cell bodies in AVT and TPc contain catecholamines; lesions of TPc greatly reduce or abolish catecholamine fluorescence in PA, and a lesion of AVT eliminates histofluorescence in LPO, including Area X. The anatomical location and catecholaminergic projection from AVT suggest that LPO‐Area X may be the avian homolog of the mammalian nucleus accumbens, olfactory tubercle, and/or rostromedial caudate.