An immunocytochemical analysis of the lateral geniculate complex in the pigeon (Columba livia)

Abstract

The lateral geniculate complex (GL) of pigeons was investigated with respect to its immunohistochemical characteristics, retinal afferents, and the putative transmitters/modulators of its neurons. The distributions of serotonin-, choline acetyltransferase-, glutamic acid decarboxylase-, tyrosine hydroxylase-, neuropeptide Y- (NPY), substance P- (SP), neurotensin- (NT), cholecystokinin- (CCK), and leucine-enkephalin- (L-ENK) like immunoreactive perikarya and fibers were mapped. Retinal projections were studied following injections of Rhodamine-B-isothiocyanate into the vitreous. Transmitter-specific projections onto the visual Wulst and the optic tectum were studied by simultaneous double-labelling of retrograde tracer molecules and immunocytochemical labelling. The GL can be divided into three major subdivisions, the n. geniculatus lateralis, pars dorsalis (GLd; previously designated as the n. opticus principalis thalami, OPT), the n. marginalis tractus optici (nMOT), and the n. geniculatus lateralis, pars ventralis (GLv). All three subdivisions are retinorecipient. The GLd can be further subdivided into at least five components differing in their immunohistochemical characteristics: n. lateralis anterior (LA); n. dorsolateralis anterior thalami, pars lateralis (DLL), n. dorsolateralis anterior thalami, pars magnocellularis (DLAmc); n. lateralis dorsalis nuclei optici principalis thalami (LdOPT); and n. suprarotundus (SpRt). The LdOPT consists of an area of dense CCK-like and NT-like terminals of probable retinal origin. Three subnuclei (DLL, DLAmc, SpRt) were shown to project to the visual Wulst. Cholinergic and cholecystokinergic relay neurons participated in this projection. The nMOT occupies a position between the GLd and GLv and encircles the rostral pole of n. rotundus and the LA. It is characterized mainly by medium sized NPY-like perikarya which were shown to project onto the ipsilateral optic tectum. Bands of NPY-like fibers in the tectal layers 2, 4, and 7 could at least in part be due to this projection of the nMOT. Most of the antisera used revealed transmitter/modulator-specific fiber systems in the GLv which often showed a layer-specific distribution. Perikaryal labelling was only obtained with glutamic acid decarboxylase. On the basis of its chemoarchitectonics, topography, and connectional pattern, the GLd complex of pigeons is most directly equivalent to the mammalian GLd. However, although the different subdivisions of the avian GLd may represent functionally different channels within the thalamofugal pathway similar to the lamina-specific differentiation within the mammalian geniculostriate projection, direct comparison of subnuclei of birds and mammals is not justified at this time. The nMOT appears similar to the intergeniculate leaflet (IGL) and the avian GLv clearly corresponds in many features to the mammalian GLv.

Serotonin 5-HT1A receptor binding sites in the brain of the pigeon (Columba livia)

“…The relatively highest density was detected in the ventral part of the lateral geniculate nucleus (Glv), which receives a strong serotonergic innervation, though to a lesser extent than PT (Cozzi et al, 1991;Challet et al, 1996). Furthermore, the Glv receives direct input from the retina and afferents from the visual Wulst, has reciprocal connections with the optic tectum, and projects to the pretectal nuclei (Guiloff et al, 1987;Güntürkün and Karten, 1991). Lesions of the Glv had shown that this area is involved in visuomotor function (Guiloff et al, 1987).…”

Do pigeons perceive the motion aftereffect? A behavioral study

“…This arrangement could be a powerful cellular mechanism to create illusory motions with the opposite direction to the previous stimulus. Since the nLM projects via the visual thalamus to the forebrain [23,24,51], it is possible that the MAE is integrated at telencephalic level to guide goal-directed behavior as analyzed in the present study.…”

Glutamatergic Neurotransmission from the Optic Tectum to the Contralateral Nucleus Rotundus in Pigeons

“…It appears that the nRt lacks both muscarinic and nicotinic cholinergic receptors [Dietl et al, 1988a;Watson et al, 1988;Güntürkün and Karten, 1991; Bagnoli et al, 1992]. However, this nucleus has an apparently homogenous distribution of γ-aminobutyric acid (GABA)-like terminals, which may stem from the GABAergic neurons of the subpretectal and ventral…”

“…It also receives input from the contralateral OT [Hunt and Künzle, 1976;Bischof and Niemann, 1990; Güntürkün et al, 1993;Ngo et al, 1994;Mpodozis et al, 1996]. Electrophysiological studies have shown that this nucleus is involved in the analysis of geometric pattern, brightness, color, and fine spatial detail [Hodos and Karten, 1966;Macko and Hodos, 1984] and is organized into several functionally distinct subdivisions for processing different types of visual information such as color, luminance and Z-axis motion [Wang and Frost, 1992;Wang et al, 1993].Histochemically, the nRt subdivisions stain differentially for acetylcholinesterase (AChE) [Martinez-de-la-Torre et al, 1990] but fail to label for choline acetyltransferase (ChAT) [Güntürkün and Karten, 1991]. It appears that the nRt lacks both muscarinic and nicotinic cholinergic receptors [Dietl et al, 1988a;Watson et al, 1988;Güntürkün and Karten, 1991; Bagnoli et al, 1992].…”