Developmental changes of NADPH-diaphorase positive structures in the isthmic nuclei of the chick

Abstract

Nicotine adenine dinucleotide phosphate-diaphorase staining was used to study nitric oxide synthase activity and distribution in the midbrain visual structures of white leghorn chick embryos and post-hatched chickens. Enzyme staining first appeared in the isthmic region at the tenth embryonic day (E10) in the neuropil of the nucleus isthmi, pars parvocellularis. At E11 faint enzyme positivity appeared also in the nucl. isthmi pars magnocellularis, the nucl. semilunaris and the nucl. isthmo-opticus. The staining intensity of the isthmic nuclei dramatically increased between the 12.5th and the 13th days of incubation. The nucl. isthmi, pars parvocellularis showed the strongest enzyme reaction throughout embryonic life. A day before hatching all the isthmic nuclei were heavily stained, however, nicotine adenine dinucleotide phosphate-diaphorase-positive cells occurred exclusively in the nucleus isthmo-opticus. In the tectum opticum, intensely stained cells occupied the stratum fibrosum et griseum superficiale. The layer containing the projection neurons to the isthmo-optic nucleus was unstained. In the isthmic region, the intensity of staining surpassed that of the tectum and reached its maximum at E17 and then slowly decreased till the end of the experimental period (120 days post-hatched). The tractus isthmo-opticus showed nicotine adenine dinucleotide phosphate-diaphorase activity throughout the investigated period of life of the chicken, but the tractus tectoisthmo-opticus was unstained. Our results suggest that in the isthmic nuclei, nicotine adenine dinucleotide phosphate-diaphorase-positive neurons occur only in the isthmo-optic nucleus and optic tectum. The other positively stained structures are the fibers and terminals of tectal cells. In most brain areas nicotine adenine dinucleotide phosphate-diaphorase indicates nitric oxide synthase that produces nitric oxide. The transient appearance of this molecule is probably necessary for neuronal differentiation or the establishment of synaptic connections in the isthmic nuclei, and these developmental changes are under the control of the optic tectum.

Identification of neurons with acetilcholinesterase and NADPH-diaphorase activities in the centrifugal visual system of the chick

“…Indeed, other authors have proposed that structures using NO project onto the nucleus (Miceli et al, 1999). In parallel, it has been suggested that the ION itself could use NO as a neurotransmitter or a neuromodulator (Morgan et al, 1994;Blute et al, 1997;Xiao et al, 2000). In agreement with these previous works we observed cell bodies showing NADPH-diaphorase activity in both the ION and the Ecn.…”

“…These studies show contrasting evidences related to localization of NADPH-diaphorase neurons in ION. While it has not been found in the ION of quail and mouse (Bruning, 1993;Panzica et al, 1994), NADPH-diaphorase neurons within the ION and optic tectum have been shown in the budgie and in chick up to P7 (Cozzi et al, 1997;Xiao et al, 2000). In fact, we were interested in evaluating not only the presence of NADPH-diaphorase neurons in ION and Ecn but also whether they were interneurons participating of a local circuit or retinal projecting neurons of the CVS.…”

“…NADPH-diaphorase neurons were found at all levels of the visual system (for a review, Cudeiro and Rivadulla, 1999), which suggests that NO plays an important regulatory role in visual function. Interestingly, NADPH-diaphorase activity has been detected in the ION of different species (Bruning, 1993;Panzica et al, 1994;Cozzi et al, 1997;Xiao et al, 2000). NO is known to exert several important functions during development, such as modulation of proliferation, cell death and neuritogenesis (Lepoivre et al, 1990;Peunova and Enikolopov, 1995;Zhang and Snyder, 1995;Packer et al, 2003).…”

Ontogeny of NADPH diaphorase/nitric oxide synthase reactivity in the brain of Xenopus laevis

“…Blockade of NOS interferes with normal pattern formation in the lateral geniculate nucleus of the ferret (Cramer et al, 1995), the chick retinotectal system (Wu et al, 1994), and retinal projections in Drosophila (Gibbs and Truman, 1998). In chick embryos, peak expression of NOS in tectal cells coincides with the refinement of initial synaptic connections, and NO might be an important factor in this process (Williams et al, 1994;Xiao et al, 2000). However, in ranid frogs, it was shown that NO has some signaling function in the retinotectal pathway, but this function is not critical to the mechanism that refines the projection (Renteria and Constantine-Paton, 1999).…”

Increased expression of nitric oxide synthase in visual structures of the chick brain after retinal removal

“…More recently, the nitrinergic system has also been suggested to play a role in morphogenetic processes of the nervous system, such as synapse formation and patterning and refinement of synaptic connections (Ernst et al, 1998). This hypothesis emerged from studies that have shown a transient expression of the NO‐synthesizing enzyme NO synthase (NOS) in some areas of the nervous system (Bredt and Snyder, 1994; Williams et al, 1994; Cramer et al, 1995; Tenório et al, 1995; Cork et al, 2000; Xiao et al, 2000). Curiously, the process of refinement of connections seems to be similar to some mechanisms of neuronal plasticity, such as long‐term potentiation in the adult hippocampus, which also seems to involve NO as a retrograde messenger (Haley et al, 1992).…”