Peptides in frog brain areas processing visual information

Abstract

Vision is the most important sensory modality to anurans and a great deal of work in terms of hodological, physiological, and behavioral studies has been devoted to the visual system. The aim of this account is to survey data about the distribution of peptides in primary (lateral geniculate complex, pretectum, tectum) and secondary (striatum, anterodorsal and anteroventral tegmental nuclei, isthmic nucleus) visual relay centers. The emphasis is on general traits but interspecies variations are also noted. The smallest amount of peptide-containing neuronal elements was found in the lateral geniculate complex, where primarily nerve fibers showed immunostaining. All peptides found in the lateral geniculate complex, except two, occurred in the pretectum together with four other peptides. A large number of neurons showing intense neuropeptide thyrosine-like immunoreactivity was characteristic here. The mesencephalic tectum was the richest in peptide-like immunoreactive neuronal elements. Almost all peptides investigated were present mainly in fibers, but 9 peptides were found also in cells. The immunoreactive fibers show a complicated overlapping laminar arrangement. Cholecystokinin octapeptide, enkephalins, neuropeptide tyrosine, and substance P (not discussed here) gave the most prominent immunoreactivity. Several peptides also occur in the tectum of fishes, reptiles, birds, and mammals. Peptides in various combinations were found in the striatum, the anterodorsal- and anteroventral tegmental nucleus, and the isthmic nucleus that receive projections from the primary visual centers. The functional significance of peptides in visual information processing is not known. The only exception is neuropeptide tyrosine, which was found to be inhibitory on retinotectal synapses.

The effects of nicotinic and muscarinic receptor activation on patch-clamped cells in the optic tectum of rana pipiens

“…Linking these responses to the apparent facilitatory effects of cholinergic activity on the tectum as a whole is difficult at this point. Part of this difficulty comes from the fact that layer six contains many different populations of cells Tostivint et al, 1996;Gabriel et al, 1998;Li and Fite, 1998;Lázár, 2001;Stuesse et al, 2001) and we do not know how any of these cell types function in generating the overall tectal response. Thus it is unclear, for example, how the muscarinic receptor-mediated inhibition of some layer 6 cells will affect overall tectal activity patterns.…”

Neurochemistry and circuit organization of the lateral spiriform nucleus of birds: A uniquely nonmammalian direct pathway component of the basal ganglia

“…This region in frogs is typically called the posterior thalamic nucleus (Kozicz & Lazar, 1994). Like sauropsid PT, frog PT neurons contain NPY (Kozicz & Lazar, 1994; Lazar, 2001; Lazar et al., 1993), are GABAergic (Brox et al., 2003b), and are reciprocally connected with the tectum (Chapman & Debski, 1995; Kozicz & Lazar, 1994), with the PT input ending in retinorecipient layers (Kozicz & Lazar, 1994; Kuljis & Karten, 1982). This input may be responsible for the disinhibitory effect of pretectal lesions on visual receptive field size of frog tectal neurons and the abnormalities in target‐directed prey catching such lesions cause (Ingle, 1986; Marin et al., 1997d, 1998c).…”

“…Consistent with a GABAergic input, the region of pretectum containing amphibian SpL is enriched in GAD+ terminals (Yucel et al., 1988) and GABAA receptors (Aller et al., 1997). The precise tectal target neurons of amphibian SpL have not been established, but, like in sauropsids, a dense network of ENK+ fibers that may arise from amphibian SpL overlaps the deeper tectal layers that contain the cell bodies of origin for the descending tectobulbar projections (Hughes, 1990; Kuljis & Karten, 1982; Lazar, 2001; Merchenthaler et al., 1987, 1989). The tectobulbar neurons in amphibians are remarkably similar in their morphology and the courses of their axonal projections to those in amniotes (Hughes, 1990; Lazar et al., 1983; Masino & Grobstein, 1989a, 1989b, 1990; Rubinson, 1968; Smeets, 1991; Ten Donkelaar et al., 1981), emphasizing a likely common role of the SpL input among birds, reptiles, and amphibians.…”

Modulation of visual perception and action by forebrain structures and their interactions in amphibians

“…The investigations on neuropeptide-like immunoreactivity in the frog's brain substantiate pretectotectal projections that involve neuropeptide Y (NPY) as neurotransmitter/modulator [62][63][64][65]. Kozicz and Lázár [66] convincingly showed in Rana esculenta that NPY immunoreactive fibers in the superficial tectum (layer 9: lamina C dense, D-F sparse) originate from the ipsilateral Lpd and Lpv nuclei, i.e.…”

“…The Y 2 receptor mediated NPY effects of presynaptic inhibition of glutamate release are the most abundant and may have an evolutionary conserved role in modulating visuomotor processing (e.g., see [65,70,133]). The Y 2 receptor mediated NPY effects of presynaptic inhibition of glutamate release are the most abundant and may have an evolutionary conserved role in modulating visuomotor processing (e.g., see [65,70,133]).…”