A quantitative study of the neuronal nitric oxide synthase expression in the superficial layers of the adult rat superior colliculus after perinatal enucleation

Abstract

The level of expression of the neuronal nitric oxide synthase (nNOS) in the retinorecipient layers of rat superior colliculus (SC) was investigated in adult rats after neonatal enucleation using two biochemical methods: (1) measurement of the in vitro specific-activity of NOS by the conversion of [3H]-arginine to [3H]-citrulline and (2) immunochemical analysis by western blotting and densitometry of immunoreactive bands using antibodies that recognise the three prominent isoforms of nNOS, alpha, beta and gamma. A total of 20 Lister rats were used in this study. We have shown that the deprivation of the retinocollicular projections at early postnatal ages induces no significant change in the specific-activity of nNOS. We also have shown that the deafferentation does not significantly influence either the total amount of nNOS in the SC superficial layers or the relative contribution ratio of nNOS isoforms. In conclusion, the expression and activity of nNOS in the SC retinorecipient layers was shown not to be dependent on the presence of retinal afferents during development.

Differential regulation of the neuronal isoform of nitric oxide synthase in the superior colliculus and dorsal lateral geniculate nucleus of the adult rat brain following eye enucleation

“…There are, however, reports on nNOS down‐regulation after monocular enucleation in the rat (Batista et al, 2003; Zhang et al, 1996), and visual deprivation (Aoki et al, 1993) or inhibition of retinal activity (Wong‐Riley et al, 1998) in primates. In addition, de Bittencourt‐Navarrete et al (2004) have shown that unilateral enucleation does not change the total amount or the activity of nNOS in the SC, but only its distribution within neurons. There is apparently no simple explanation for these discrepant findings, although different ages, different species, and different protocols are some of the possible reasons subjacent to those different findings.…”

“…The present study involved only adult rats, and the results therefore reveal a marked plasticity of the nitrinergic system even in the adult stage. Other rat studies employed Lister (Batista et al, 2003; de Bittencourt‐Navarrete et al, 2004) or Long‐Evans (Nucci et al, 2000; Zhang et al, 1996) strains, but most of those experiments have also been conducted in newborn or young animals. The possibility of age playing a major role in those apparently discrepant findings is supported by the data from two different studies in the same species.…”

“…Controls for immunostaining included the omission of the primary antibody, and its substitution for normal mouse serum, which completely eliminated staining. It should be stressed that the antibody used here has been extensively tested and characterized (de Bittencourt‐Navarrete et al, 2004; Torrão and Britto, 2004), and it is known to recognize the nNOSα isoform, which is the most prevalent nNOS isoform in the brain (Eliasson et al, 1997).…”

“…Several lines of evidence have established a wide variety of functions for nitric oxide (NO) as an important molecule in neurotransmission, neurotoxicity, and neural plasticity (de Bittencourt‐Navarrete et al, 2004). In the central nervous system, NO can be either beneficial or detrimental, depending on the cellular status (Cudeiro and Rivadulla, 1999), suggesting that the expression of neuronal NO synthase (nNOS), one of the three NO synthase isoforms, is accurately controlled into neurons.…”

NMDA receptor blockade alters the intracellular distribution of neuronal nitric oxide synthase in the superficial layers of the rat superior colliculus

“…It has been shown that lack of neural activity produces changes in the intracellular distribution of nNOS in neurons of the SC (17,18). Despite the results of Zhang and co-workers (14) showing that eye removal causes a down-regulation of NADPH-d-positive neurons in the SC, the expression level of the different NADPH-d transcripts seems to be independent of such activity (19).…”