Journal of Chemical Neuroanatomy 22 (2001) 139 – 146 Distribution of calbindin, parvalbumin and calretinin in the lateral geniculate nucleus and superior colliculus in Cebus apella monkeys Juliana G.M. Soares, Elia˜ P. Botelho, Ricardo Gattass * Departamento de Neurobiologia, Instituto de Biofı ´sica Carlos Chagas Filho, Uniersidade Federal do Rio de Janeiro, CCS, Bloco G, Ilha do Funda˜o, Rio de Janeiro, 21941 -900, Brazil Received 18 December 2000; received in revised form 7 March 2001; accepted 15 May 2001 Abstract We studied the distribution of the calcium-binding proteins calbindin, parvalbumin and calretinin, in the superior colliculus and in the lateral geniculate nucleus of Cebus apella, a diurnal New World monkey. In the superior colliculus, these calcium-binding proteins show different distribution patterns throughout the layers. After reaction for calretinin one observes a heavy staining of the neuropil with few labeled cells in superficial layers, a greater number of large and medium-sized cells in the stratum griseum intermediale, and small neurons in deep layers. The reaction for calbindin revealed a strong staining of neuropil with a large number of small and well stained cells, mainly in the upper half of the stratum griseum superficiale. Intermediate layers were more weakly stained and depicted few neurons. There were few immunopositive cells and little neuropil staining in deep layers. The reaction for parvalbumin showed small and medium-sized neurons in the superficial layers, a predominance of large stellate cells in the stratum griseum intermediale, and medium-sized cells in the deep layers. In the lateral geniculate nucleus of Cebus, parvalbumin is found in the cells of both the P and M pathways, whereas calbindin is mainly found in the interlaminar and S layers, which are part of the third visual pathway. Calretinin was only found in cells located in layer S. This pattern is similar to that observed in Macaca, showing that these calcium-binding proteins reveal different components of the parallel visual pathways both in New and Old World monkeys. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Calcium-binding proteins; Visual system; Visual subcortical nuclei; Primates www.elsevier.com/locate/jchemneu 1. Introduction The use of immunohistochemical methods in the study of subcortical structures gives additional data allowing interspecies comparison of functional proper- ties in structurally homologous regions. Calbindin (Cb), parvalbumin (Pv) and calretinin (Cr) are calcium-bind- ing proteins (CaBPs) which have been found in various regions of the central nervous system. They are selec- tively distributed in many subcortical nuclei as well as in various cortical areas, where they seem to be related with distinct neural pathways and functions (Jones and Hendry, 1989; Celio, 1990; Hof and Nimchinsky, 1992). In the lateral geniculate nucleus (LGN) of primates, Pv is found in relay cells of both the P and M path- ways, whereas Cb is found mainly in the S layers and in the interlaminar zones, which belong to the third visual pathway (Jones and Hendry, 1989; Tigges and Tigges, 1991; Mize et al., 1992; Casagrande, 1994; Johnson and Casagrande, 1995; Goodchild and Martin, 1998). Calre- tinin-immunoreactive (Cr-IR) cells are concentrated in the S layers (Yan et al., 1996). Complementary tiers of calbindin-immunoreactive (Cb-IR) and parvalbumin-immunoreactive (Pv-IR) cells have also been observed in the superior colliculus (SC) of the rat (Cork et al., 1998) and cat (Mize et al., 1991, 1992). This complementary pattern, however, has not Abbreiations: CaBPs, calcium-binding proteins; Cb, calbindin; Cr, calretinin; ILZ, interlaminar zone; IR, immunoreactive; LGN, lateral geniculate nucleus; M, magnocellular laminae; P, parvocellular lami- nae; PAG, periaquedutal gray; PBS, phosphate-buffered saline; PI L , pulvinar inferior lateral; PI M , pulvinar inferior medial; Pv, parvalbu- min; S, superficial laminae; SC, superior colliculus; SGI, stratum griseum intermediale; SGP, stratum griseum profundum; SGS, stra- tum griseum superficiale; SO, stratum opticum; SZ, stratum zonale. * Corresponding author. Tel.: +55-21-290-6897; fax: +55-21-280- 8193. E-mail address: rgattass@biof.ufrj.br (R. Gattass). 0891-0618/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII: S0891-0618(01)00123-5