Plasticity of brain in normal adult some earth-dwelling Anamnia and terrestrial Amniota: further review on the trend of seasonal environmental influence on encephalic proliferation, as revealed by immunohistochemistry

The immunohistochemical evidence provided by the present authors about the persistence of latent naturai brain proliferative potentially in adult vertebrate brain and its response to cyclic seasonal environmental fluctuations (temperature, photoperiod) has been reviewed. These stimuli elicit an otherwise hidden mitotic activity thanks to stem cells still present especially in less high vertebrates like Triturus carni/ex, Rana bergeri, Podarcis sicula. The evidence gathered from specimens caught in the wild in spring, summer and autumn has been compared with previous evidence on specimens of newts, frogs and lizards. Signs of proliferation were mainly observed in the typical sites (olfactory bulbs/peduncles, telencephalic hemispheres) occupied by cells in mitotic stand-by. The findings have shown increasing labelling from spring to summer to autumn with minor differences among species, and have confirmed that in adulthood the proliferative therefore the reparative and even the regenerative power of brain cells is highest in urodela (the vertebrates best equipped with quiescent cells), intermediate in anura and lowest in lacertilian Reptiles.