Relationships between seasonal (spring or autumnal) thermal variations and cell proliferation in heterothermic vertebrates, as revealed by PCNA expression in the brain of adult Rana bergeri (Günther, 1986)

The question has arisen if the seasonal cycle, made of temperature and photoperiod variations, might activate proliferation of quiescent stem cells still present in adult brain of some living in fresh water, earth-dwelling Anamnia and heterothermic Amniota. Previously, some authors performed seminal autoradiographic, quantitative observations focused on a handful of adult Rana esculenta specimens which, once caught in nature in spring and autumn, were submitted to temporary artificial hibernation and compared with untreated controls. In not-brain-injured and not-cold-shocked samples the encephalic proliferation appeared lower in frogs caught in spring than in those caught in autumn. At the light of these data, an immunohistochemical investigation has been carried on not-brain-injured, not-cold-stressed adult Rana bergeri, captured in their habitat in spring and in autumn. The labelling was observed mainly in the forebrain, where it was more pronounced in the specimens caught in autumn than in those captured in spring. This pattern confirms and reinforces the findings of past authors in the same species and under similar experimental conditions.