Retinofugal Projections Into Visual Brain Structures in the Bat Artibeus planirostris: A CTb Study.

A well-developed visual system can provide significant sensory information to guide motor behavior, especially in fruit-eating bats, which usually use echolocation to navigate at high speed through cluttered environments during foraging. Relatively few studies have been performed to elucidate the organization of the visual system in bats. The present work provides an extensive morphological description of the retinal projections in the subcortical visual nuclei in the flat-faced fruit-eating bat (Artibeus planirostris) using anterograde transport of the eye-injected cholera toxin B subunit (CTb), followed by morphometrical and stereological analyses. Regarding the cytoarchitecture, the dorsal lateral geniculate nucleus (dLGN) was homogeneous, with no evident lamination. However, the retinal projection contained two layers that had significantly different marking intensities and a massive contralateral input. The superior colliculus (SC) was identified as a laminar structure composed of seven layers, and the retinal input was only observed on the contralateral side, targeting two most superficial layers. The medial pretectal nucleus (MPT), olivary pretectal nucleus (OPT), anterior pretectal nucleus (APT), posterior pretectal nucleus (PPT) and nucleus of the optic tract (NOT) were comprised the pretectal nuclear complex (PNT). Only the APT lacked a retinal input, which was predominantly contralateral in all other nuclei. Our results showed the morphometrical and stereological features of a bat species for the first time.

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.

Retinal, NPY- and 5ht- inputs to the aged suprachiasmatic nucleus in common marmosets (Callithrix jacchus).

The circadian timing system (CTS) anticipates optimal physiological patterns in response to environmental fluctuations, such as light-dark cycle. Since age-related disruption of circadian synchronization is linked to several pathological conditions, we characterized alterations of neurochemical constituents and retinal projections to the major pacemaker of CTS, the suprachiasmatic nucleus (SCN), in adult and aged marmosets. We used intraocular injections of neural tracer Cholera toxin b (CTb) to report age-related reductions in CTb, neuropeptide Y and serotonin immunoreactivities. Considering these projections arise in SCN from nuclei that relay environmental information to entrain the circadian clock, we provide important anatomical correlates to age-associated physiological deficits.

Morphological changes in the suprachiasmatic nucleus of aging female marmosets (Callithrix jacchus).

The suprachiasmatic nuclei (SCN) are pointed to as the mammals central circadian pacemaker. Aged animals show internal time disruption possibly caused by morphological and neurochemical changes in SCN components. Some studies reported changes of neuronal cells and neuroglia in the SCN of rats and nonhuman primates during aging. The effects of senescence on morphological aspects in SCN are important for understanding some alterations in biological rhythms expression. Therefore, our aim was to perform a comparative study of the morphological aspects of SCN in adult and aged female marmoset. Morphometric analysis of SCN was performed using Nissl staining, NeuN-IR, GFAP-IR, and CB-IR. A significant decrease in the SCN cells staining with Nissl, NeuN, and CB were observed in aged female marmosets compared to adults, while a significant increase in glial cells was found in aged marmosets, thus suggesting compensatory process due to neuronal loss evoked by aging.

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.