IMMUNOCYTOCHEMICAL CHANGES OF CYTOSKELETON COMPONENTS AND CALMODULIN IN THE FROG CEREBELLUM AND OPTIC TECTUM DURING HIBERNATION

During hibernation, variation in the metabolism of nerve cells occurs. Since the cytoskeleton plays an important role in nerve cell function , we have analyzed the immunocytochemical expression of two cytoskelet on components, i.e. phosphorylated 200 kDa neurofilament protein, and microtubule-associated protein 2 in the cerebellum and optic tectum of hibernating frogs (Rana esculenta) in comparison with active animals. In addition, we have considered the immunocytochemical expression of calmodulin, which is known to be involved in neurofilament phosphoryla tion. In hibernating animals, there was a decrease in the immunoreacti vity for phosphorylated 200 kDa neurofilament protein and microtubule- associated protein 2 of fibers in both the cerebellum and in the optic tectum. In contrast, in the large neurons of the cerebellum, i.e. Pur kinje neurons, there was an increase in the immunoreactivity for micro tubule-associated protein 2. The changes in the cytoskeleton component s were accompanied by a decrease in calmodulin immunoreactivity in the cytoplasm of nerve cells of the cerebellum. All the changes observed are consistent with a low neuronal activity during hibernation, as als o indicated by previous microdensitometric and microfluorometric data. This shows a higher degree of chromatin condensation in hibernating a nimals and suggests that hibernation represents a simple form of neuro nal plasticity. (C) 1998 Elsevier Science B.V. All rights reserved.