Comparative anatomy of the retino-hypothalamic tract in photoperiodic and non-photoperiodic rodents.
This study examined whether the nearly symmetrical input from each eye to each suprachiasmatic nucleus previously reported in Syrian hamsters (Mesocricetus auratus) is a universal feature of retino-hypothalamic projections in photoperiodic rodents. Intraocular injections of horseradish peroxidase (HRP) were used to trace the retino-hypothalamic tract in three species of photoperiodic rodents, Turkish hamster (Mesocricetus brandti), deer mouse (Peromyscus maniculatus bairdi) and white-footed mouse (Peromyscus leucopus), and in the non-photoperiodic house mouse (Mus musculus). The Turkish hamster displayed a pattern of retinal input to the suprachiasmatic nuclei (SCN) similar to that previously seen in the Syrian hamster. On the other hand, the two photoperiodic species of Peromyscus used in the study showed an asymmetrical distribution of retinal fibers with the heaviest input to each suprachiasmatic nucleus originating from the contralateral eye. This asymmetrical pattern was also evident in house mice and is similar to that previously seen in rats. Therefore, symmetrical retinal input to the SCN is not consistently related to photoperiodism in rodents.
D000818:Animals; D006224:Cricetinae; D006735:Horseradish Peroxidase; D008027:Light; D008297:Male; D008647:Mesocricetus / Q000033:anatomy & histology; D051379:Mice / Q000033:anatomy & histology; D009434:Neural Pathways / Q000033:anatomy & histology; D010507:Periodicity; D010542:Peromyscus / Q000033:anatomy & histology; D012160:Retina / Q000033:anatomy & histology*; D012377:Rodentia / Q000033:anatomy & histology*; D013194:Staining and Labeling; D013493:Suprachiasmatic Nucleus / Q000033:anatomy & histology*
D006735:Horseradish Peroxidase