Nitric oxide synthase‐positive neurons in the rat superior colliculus: Colocalization of NOS with NMDAR1 glutamate receptor, GABA, and parvalbumin

Abstract

We analyzed the potential input and output components of nitric oxide synthase (NOS)-containing neurons in the rat superior colliculus (SC). To identify whether NOS-positive neurons receive glutamatergic input we investigated the colocalization of NOS with NMDA receptor subunit R1 (NMDAR1). In addition, to examine whether putative nitric oxide synthesizing neurons represent a neurochemically specific or distinct subpopulation of cells in the SC we studied the colocalization of NOS with the neurotransmitter GABA, the calcium-binding proteins parvalbumin, calbindin and calretinin and with neuropeptides such as somatostatin, substance P and neuropeptide Y. We found that 90% of NOS-positive neurons in the superficial layers of the rat SC express NMDAR1. Nearly 20% of the population of nitridergic neurons also expresses GABA and 15% of them express parvalbumin. NOS-positive neurons in the superior colliculus did not contain calretinin, calbindin or either of the neuropeptides tested. The results of this study show that the capacity for synthesizing NO in the SC is largely restricted to neurons that receive glutamatergic inputs and that some of these neurons express GABA or parvalbumin.

Expression of neuronal nitric oxide synthase in the developing superficial layers of the rat superior colliculus

“…Thus, NADPH-d histochemistry after fixation with GLUT or immunohistochemistry was apparently more sensitive than NADPH-d histochemistry after fixation with 4% PF in detecting the lower levels of nNOS at P5. However, in adulthood the number of stained cells dramatically increased ( Figure 2D), as also reported previously (19,21,27,28).…”

“…In the rat, a subpopulation of all the different cell types described in the superficial layers of the superior colliculus by the Golgi technique (26) expresses nNOS (21,27,28). Previous studies have also shown that the first NOSpositive cells in these layers appear by the end of the first postnatal week (between the fifth and the seventh postnatal day).…”

Removal of the cortical projections alters expression of NOS in the different cell types of the superficial layers of the superior colliculus in rats

“…In various mammalian species, the SC superficial layers contain the highest amount of GABA, and the main source of this neurotransmitter in these layers is the large number of GABAergic interneurons (Mize et al 1982, Okada 1974. We have previously shown that 20% of all NOS-positive cells in the rat SC superficial layers also expressed GABA (Soares-Mota et al 2001). It is difficult at this time to establish any correlation between these data, and work in our lab is in progress to deter-mine which collicular cell types are double-stained by NOS and GABA, and what are the effects of the ablation of the visual cortical and retinal afferents in this co-expression.…”

Distinct types of nitric oxide–producing neurons in the developing and adult mouse claustrum

“…In this sense, colocalization between nNOS and the functionally fundamental NMDAR1 subunit has been shown in neurons in certain regions of the rat brain, such as the spinal trigeminal nucleus (Dohrn and Beitz, 1994), nucleus tractus solitarii (Lin and Talman, 2000), the cerebral cortex (Aoki et al, 1997), or nucleus accumbens (Gracy and Pickel, 1997). In addition, many nNOS-expressing neurons in different brain regions express substantial amounts of the NMDAR1 (Price et al, 1993;Zhang and Wong-Riley, 1996;Soares-Mota et al, 2001).…”