C. Vignola et al., THE CEREBRAL NEURONS OF HELIX-ASPERSA DURING HIBERNATION - CHANGES INTHE CYTOCHEMICAL DETECTION OF CALMODULIN, CYTOSKELETAL COMPONENTS ANDPHOSPHATASES, Tissue & cell, 27(2), 1995, pp. 185-196
Some markers of the intracellular systems that regulate neuronal activ
ity and morphology were analyzed in the cerebral ganglion of hibernati
ng snails (Helix aspersa), in comparison with active animals. The immu
nocytochemical expression of a calcium-binding protein, i.e. calmoduli
n, and some cytoskeletal components, i.e. 200 kDa phosphorylated neuro
filament protein (pNFH), microtubule associated protein 2 (MAP2) and a
lpha-tubulin were analyzed by the use of a panel of antibodies raised
against mammal antigens. Moreover, by enzymatic reactions the Ca2+-ATP
ase and alkaline phosphatase (AlPase) activities were demonstrated. In
comparison with the active phase, the hibernation induced an increase
in the immunopositivity for calmodulin in all the neurons. The increa
se may be linked to unmasking of immunoreactive epitopes due to confor
mational changes of the protein, which in turn may be a consequence of
a reduction or absence of binding with calcium ions or of a veal incr
ease in the amount of calmodulin in the somata of neurons. In any even
t, both the hypotheses indicate that neurons have decreased or suppres
sed the Ca2+-dependent mechanisms as also shown by the lower Ca2+-ATPa
se activity. Nevertheless, the AlPase activity, which was localized in
the epineural sheat, was not significantly changed during hibernation
and this supports that some metabolic activities are preserved in the
hibernated animals. Changes in the immunopositivity for cytoskeletal
components weve found. There was an increase in the epitopes recognize
d by the mammalian pNF antibody, that concerned both the positivity of
the entire cytoplasm of some clusters of metacerebral neurons and the
intensity of the reaction. This would be aimed to improve the stabili
ty of the somata and primary neurites. Moreover, the decrease of alpha
-tubulin and MAP2 immunopositivity, suggests that a disassembly of mic
rotubules have occurred. The findings indicate that the transport of v
esicles in the axons is slowed down during hibernation. In fact, resea
rch in progress show that the patterns of neurotransmission and neurom
odulation are also deeply modified.