Immunohistochemical localization of DARPP-32 in the brain of the lizard, Gekko gecko: Co-occurrence with tyrosine hydroxylase

To assess the relationship between dopaminergic neuronal structures and dop aminoceptive structures in a reptile, single and double immunohistochemical procedures with antibodies directed against DARPP-32 (dopamine- and cAMP-r egulated phosphoprotein with an apparent molecular mass of 32,000 daltons), a phosphoprotein related to the dopamine D-1-receptor, and tyrosine hydroxy lase (TH) were applied to the brain of the lizard, Gekko gecko. The DARPP-3 2 antibody yielded a well-differentiated pattern of staining in the brain o f Gekko. In general, areas that are densely innervated by TH-immunoreactive , putative dopaminergic fibers, such as the nucleus accumbens, striatum, do rsal ventricular ridge, and amygdaloid complex, display strong immunoreacti vity for DARPP-32 in somata and neuropil. Distinct cellular DARPP-32 immuno reactivity was also found in the lateral cortex, ventral hypothalamus, habe nula, central nucleus of the torus semicircularis, midbrain tectum, parvice llular isthmic nucleus, raphe nuclei, caudal rhombencephalic tegmentum, and spinal cord. Striatal projections to the midbrain and their target, i.e., the substantia nigra pars reticulata, were found to be strongly immunoreact ive. Double immunofluorescence staining revealed that dopaminergic cells ge nerally do not stain for DARPP-32, except for cells in the ventral hypothal amus and at caudal rhombencephalic levels. In conclusion, the distribution of DARPP-32 in the brain of the Lizard Gekko gecko largely resembles the pa ttern observed in birds and mammals, at least as far as basal ganglia struc tures are concerned. On the other hand, there are several specific features of DARPP-32 distribution in the gekkonid brain that deserve further attent ion, such as cellular colocalization of DARPP-32 and TK immunoreactivity in hypothalamic and caudal rhombencephalic areas, and cellular DARPP-32 immun oreactivity in the tectum and central nucleus of the torus semicircularis o f the midbrain, the superior and inferior raphe nuclei, and the spinal cord . (C) 2001 Wiley-Liss, Inc.