NEUROCHEMICAL ORGANIZATION OF THE MACAQUE RETINA - EFFECT OF TTX ON LEVELS AND GENE-EXPRESSION OF CYTOCHROME-OXIDASE AND NITRIC-OXIDE SYNTHASE AND ON THE IMMUNOREACTIVITY OF NA-I(K+ ATPASE AND NMDA RECEPTOR SUBUNIT)

The present study examined the relationship between an important energ y-generating enzyme (cytochrome oxidase; CO), a key energy-consuming e nzyme (Na(+)K(+)ATPase) and neurochemicals associated with excitatory glutamatergic synapses (NMDAR1 and neuronal nitric oxide synthase, nNO S) in the adult macaque retina. Polyclonal antibodies against neuronal nitric oxide synthase and N-methyl-D-aspartate receptor subunit I wer e generated for immunohistochemical examination and labeled sites not previously reported were found. We have also isolated cDNAs for cytoch rome oxidase subunits III (mitachondrial-encoded) and IV (nuclear-enco ded), as well as for a fragment of neuronal nitric oxide synthase, fro m a human cDNA library. The distributions of mRNAs of these genes were analyzed by in situ hybridization. We found that three or more of the markers examined coexisted in a number of sites: (a) In the inner seg ments of photoreceptors, high energy demand for maintaining the dark c urrent was placed by Na(+)K(+)ATPase. This was partially met by ATP-ge nerating enzymes such as CO. Neuronal NOS was also present there for t he synthesis of NO and the cascading event leading to the generation o f cGMP and the gating of channels for visual transduction. (b) Both th e outer and inner plexiform layers had detectable amounts of ail four markers, although the levels varied among them. This was most likely d ue to the presence of depolarizing glutamatergic synapses arising from photoreceptors and bipolar cells and such synaptic events were energy -demanding. The involvement of NMDA receptors and nNOS in these synapt ic layers is strongly implicated in the present study. (c) All four ma rkers were present in the majority of retinal ganglion cells, with som e inherent heterogeneity related to intensity and size. Retinal gangli on cells are known to receive excitatory synapses from glutamatergic b ipolar cells and are themselves highly active. The presence of both NM DAR1 and nNOS in these cells were verified in the present study and th e energy demands related to these synaptic activities were necessarily high. Thus, active ion transporting functions related to synaptic or non-synaptically induced repolarization form the basis for an interrel ationship between the neurochemicals/ enzymes studied. Finally, (d) al l four markers and the gene expression of CO and nNOS in the macaque r etina were regulated by neuronal activity. (C) 1998 Elsevier Science L td. All rights reserved.