Visual Neuroscience

Coexistence of GAD-65 and GAD-67 with tyrosine hydroxylase and nitric oxide synthase in amacrine and interplexiform cells of the primate, Cebus apella

a1 Departamento de Fisiologia e Farmacologia, CCB, UFPE, Cidade Universitária, Recife, PE, Brasil
a2 Laboratório de Neurobiologia da Retina, Instituto de Biofísica Carlos Chagas Filho, CCS, UFRJ, Cidade Universitária, Rio de Janeiro, RJ, Brasil


The expression of glutamate decarboxylase forms, GAD-65 and GAD-67, in GABAergic cells was studied by immunocytochemistry in the retina of the New World monkey, Cebus apella. In the innermost rows of the inner nuclear layer (INL), somata that express GABA correspond to about 45% of the total number of cells in the central retina and about 25% on the periphery. Three subsets of GABAergic amacrine cells were identified along the horizontal meridian: about 5% express only GAD-65 and 40% GAD-67, and approximately 50% contain both forms of GAD. In the INL, GAD-65 immunoreactivity was detected in broad bands around strata 1, 3, and 5. GAD-67 immunoreactivity was observed throughout all strata. Somata that expressed GAD-67 exclusively stratified only in narrow bands around strata 2 and 4 of the INL and colocalized with [beta]2 and [beta]3 subunits of GABA-A receptor. Interplexiform and amacrine cells that express GABA also express tyrosine hydroxylase (TH) or nitric oxide synthase (NOS). GAD-67 colocalized with TH or NOS in presumed amacrine cells of the inner plexiform layer (IPL) and ganglion cell layer (GCL). GAD-65 was expressed in the TH- and NOS-immunoreactive interplexiform and amacrine cells, respectively. Different from what has been described in other mammals, TH and NOS were coexpressed in some neurons, indicating a partial overlap in retinal cell populations containing dopamine or nitric oxide in this primate.

(Received July 12 2002)
(Accepted February 13 2003)

Key Words: Retina; GABAergic cells; New World primates; GABA-A receptors; Immunocytochemistry.

c1 Address correspondence and reprint requests to: Jan Nora Hokoç, Laboratório de Neurobiologia da Retina, Instituto de Biofísica Carlos Chagas Filho, CCS, Bloco G, Cidade Universitária, UFRJ, 21949-900 Rio de Janeiro, Brasil. E-mail: