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

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 catacholamine-containing axons and nerve terminals, as determined in histofluorescence studies. Cell bodies in AVT and TPc contain catacholamines; lesions of TPc greatly reduce or abolish catacholamine fluorescence in PA, and a lesion of AVT eliminates histofluorescence in LPO, icluding 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.