Topographic specializations of catecholaminergic cells and ganglion cells and distribution of calcium binding proteins in the crepuscular rock cavy (Kerodon rupestris) retina.

The rock cavy (Kerodon rupestris) is a crepuscular Hystricomorpha rodent that has been used in comparative analysis of retinal targets, but its retinal organization remains to be investigated. In order to better characterize its visual system, the present study analyzed neurochemical features related to the topographic organization of catecholaminergic cells and ganglion cells, as well the distribution of calcium-binding proteins in the outer and inner retina. Retinal sections and/or wholemounts were processed using tyrosine hydroxylase (TH), GABA, calbindin, parvalbumin and calretinin immunohistochemistry or Nissl staining. Two types of TH-immunoreactive (TH-IR) cells were found which differ in soma size, dendritic arborization, intensity of TH immunoreactivity and stratification pattern in the inner plexiform layer. The topographic distribution of all TH-IR cells defines a visual streak along the horizontal meridian in the superior retina. The ganglion cells are also distributed in a visual streak and the visual acuity estimated considering their peak density is 4.13 cycles/degree. A subset of TH-IR cells express GABA or calbindin. Calretinin is abundant in most of retinal layers and coexists with calbindin in horizontal cells. Parvalbumin is less abundant and expressed by presumed amacrine cells in the INL and some ganglion cells in the GCL. The topographic distribution of TH-IR cells and ganglion cells in the rock cavy retina indicate a suitable adaptation for using a broad extension of its inferior visual field in aspects that involve resolution, adjustment to ambient light intensity and movement detection without specialized eye movements.

Mediodorsal thalamic nucleus receives a direct retinal input in marmoset monkey (Callithrix jacchus): a subunit B cholera toxin study.

The mediodorsal thalamic nucleus is a prominent nucleus in the thalamus, positioned lateral to the midline nuclei and medial to the intralaminar thalamic complex in the dorsal thalamus. Several studies identify the mediodorsal thalamic nucleus as a key structure in learning and memory, as well as in emotional mechanisms and alertness due to reciprocal connections with the limbic system and prefrontal cortex. Fibers from the retina to the mediodorsal thalamic nucleus have recently been described for the first time in a crepuscular rodent, suggesting a possible regulation of the mediodorsal thalamic nucleus by visual activity. The present study shows retinal afferents in the mediodorsal thalamic nucleus of a new world primate, the marmoset (Callithrix jacchus), using B subunit of cholera toxin (CTb) as an anterograde tracer. A small population of labeled retinofugal axonal arborizations is consistently labeled in small domains of the medial and lateral periphery of the caudal half of the mediodorsal nucleus. Retinal projections in the mediodorsal thalamic nucleus are exclusively contralateral and the morphology of the afferent endings was examined. Although the functional significance of this projection remains unknown, this retina-mediodorsal thalamic nucleus pathway may be involved in a wide possibility of functional implications.

Sciatic nerve grafting and inoculation of FGF-2 promotes improvement of motor behavior and fiber regrowth in rats with spinal cord transection.

PURPOSE: Failure of severed adult central nervous system (CNS) axons to regenerate could be attributed with a reduced intrinsic growing capacity. Severe spinal cord injury is frequently associated with a permanent loss of function because the surviving neurons are impaired to regrow their fibers and to reestablish functional contacts. Peripheral nerves are known as good substrate for bridging CNS trauma with neurotrophic factor addition. We evaluated whether fibroblastic growth factor 2 (FGF-2) placed in a gap promoted by complete transection of the spinal cord may increase the ability of sciatic nerve graft to enhance motor recovery and fibers regrow. METHODS: We used a complete spinal cord transection model. Rats received a 4 mm-long gap at low thoracic level and were repaired with saline (control) or fragment of the sciatic nerve (Nerve) or FGF-2 was added to nerve fragment (Nerve+FGF-2) to the grafts immediately after complete transection. The hind limbs performance was evaluated weekly for 8 weeks by using motor behavior score (BBB) and sensorimotor tests-linked to the combined behavior score (CBS), which indicate the degree of the motor improvement and the percentage of functional deficit, respectively. Neuronal plasticity were evaluated at the epicenter of the injury using MAP-2 and GAP-43 expression. RESULTS: Spinal cord treatment with sciatic nerve and sciatic nerve plus FGF-2 allowed recovery of hind limb movements compared to control, manifested by significantly higher behavioral scores. Higher amounts of MAP-2 and GAP-43 immunoreactive fibers were found in the epicenter of the graft when FGF-2 was added. CONCLUSIONS: FGF-2 added to the nerve graft favored the motor recovery and fiber regrowth. Thus, these results encourage us to explore autologous transplantation as a novel and promising cell therapy for treatment of spinal cord lesion.

Topographic analysis of the ganglion cell layer in the retina of the four-eyed fish Anableps anableps.

Fish of the genus Anableps (Anablepidae, Cyprinodontiformes) have eyes that are adapted for simultaneous aerial and aquatic vision. In this study we investigate some of the corresponding retinal specializations of the adult Anableps anableps eye using retinal transverse sections and wholemounts. The linear dimensions of the retina were found to be asymmetric with a greater representation of the dorsal compared to the ventral visual field. The total number of neurons in the ganglion cell layer of the ventral hemiretina was on average 3.6 times greater than the values obtained in the dorsal hemiretina. Isodensity contour maps revealed a prominent horizontal visual streak in the ventral hemiretina with an average peak cell density of 18,286 cells/mm(2). A second less-well-developed horizontal visual streak was also observed in the dorsal hemiretina. A sub-population of large cells with soma areas between 74 and 188 microm(2) was identified and found to be distributed evenly across both hemiretinas. Together, these results show that the sampling gain of the ventral retina is significantly greater than the dorsal segment, that retinal specializations important for mediating acute vision are present in the parts of the visual field immediately above and below the surface of the water, and that visual functions related with the large ganglion cells require more even sampling across the visual field. The relevance of these retinal specializations to the feeding and other behavioral strategies adopted by Anableps is discussed.

GFAP expression in astrocytes of suprachiasmatic nucleus and medial preoptic area are differentially affected by malnutrition during rat brain development.

The aim of the present study was investigate, in young rats, the effects of malnutrition on astrocyte distribution of two hypothalamic regions, the circadian pacemaker suprachiasmatic nucleus (SCN) and the medial preoptic area (MPA). Control rats were born from mothers fed on commercial diet since gestation and malnourished rats from mothers fed on multideficient diet, from the beginning of gestation (GLA group) or from the onset of lactation (LA group). After weaning, pups received ad libitum the same diet as their mothers, and were maintained under a 12/12 h light/dark cycle. The animals were analyzed either at 30-33, or 60-63 days of life. Brain coronal sections (50 microm) were processed to visualize glial fibrillary acidic protein (GFAP) immunoreactivity. Compared to control rats, both malnourished groups of 30 and 60 days exhibited a reduced number of GFAP-immunoreactive astrocytes in the SCN. The total GFAP-immunoreactive area in the SCN of the GLA group differed from the control group at both age ranges analyzed. The GFAP expression as measured by the relative optical density (ROD) exhibited a 50-60% reduction in the MPA in both malnourished groups, compared to controls. The results suggest that malnutrition early in life leads to alterations in gliogenesis or glial cell proliferation in both nuclei, being these alterations greater in the MPA. Compensatory plasticity mechanisms in the GFAP-expression seem to be developed in the astrocyte differentiation process in the SCN, especially when the malnutrition is installed from the lactation.