Retinal projections to the thalamic paraventricular nucleus in the rock cavy (Kerodon rupestris).
The thalamic paraventricular nucleus (PVT) receives afferents from numerous brain areas, including the hypothalamic suprachiasmatic nucleus (SCN), considered to be the major circadian pacemaker. The PVT also sends projections to the SCN, limbic system centers and some nuclei involved in the control of the Sleep-Wake cycle. In this study, we report the identification of a hitherto not reported direct retinal projection to the PVT of the rock cavy, a typical rodent species of the northeast region of Brazil. After unilateral intravitreal injections of cholera toxin subunit B (CTb), anterogradely transported CTb-immunoreactive fibers and presumptive terminals were seen in the PVT. Some possible functional correlates of the present data are briefly discussed, including the role of the PVT in the modulation of the circadian rhythms by considering the reciprocal connections between the PVT and the SCN. The present work is the first to show a direct retinal projection to the PVT of a rodent and may contribute to elucidate the anatomical substrate of the functionally demonstrated involvement of this midline thalamic nucleus in the modulation of the circadian timing system.
Nascimento
Expedito S
ES
Department of Morphology/Laboratory of Chronobiology, Biosciences Center, Federal University of Rio Grande do Norte, 59072-970, Natal-RN, Brazil. expeditojunior@click21.com.br
Duarte
Renata B
RB
Silva
Sebastião F
SF
Engelberth
Rovena C G J
RC
Toledo
Cláudio A B
CA
Cavalcante
Jeferson S
JS
Costa
Miriam S M O
MS
D000818:Animals; D001369:Axons / Q000502:physiology / Q000648:ultrastructure*; D001931:Brain Mapping; D002772:Cholera Toxin; D002940:Circadian Rhythm / Q000502:physiology*; D007150:Immunohistochemistry; D020644:Midline Thalamic Nuclei / Q000166:cytology* / Q000502:physiology; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D012160:Retina / Q000166:cytology / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000166:cytology* / Q000502:physiology; D012377:Rodentia / Q000033:anatomy & histology* / Q000502:physiology; D013045:Species Specificity; D013194:Staining and Labeling; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000502:physiology; D014795:Visual Pathways / Q000166:cytology* / Q000502:physiology
D002772:Cholera Toxin