Masaoki Imazawa

Inositol Trisphosphate (IP,) Receptors and Epileptic Seizure

The effects of anticonvulsants and Ca2+ channel antagonists on the inositol trisphosphate (IP3) binding and IP3-induced Ca2+ release were examined in brain membrane fractions. Anticonvulsant (PHT and valproate) and Ca2+ channel antagonists (verapamil, diltiazem, flunarizine, nicardipine and cinnarizine), examined did not significantly inhibit the IP3-receptor binding. The Kd and Bmax values of the IP3 binding did not change significantly in the various brain regions of the amygdala-kindled rats, killed 10 days after the last seizure, compared to those of controls. On the other hand, PHT, PB and carbamazepine inhibited the Ca2+ releasing activity of IP3 in the cerebellar membrane fractions by approximately 20% at therapeutic concentrations.

Unusual morphological changes in cultured oligodendrocytes induced by cytochalasin B

When cultured chick oligodendrocytes were treated with more than 1 microM of cytochalasin B (CB), an unusual effect, namely the extension of curly processes, was observed in a dose-dependent manner within 2 h after CB was added, that is, the processes with long, thin and curled shapes developed. The effect was found to be reversible and to be inhibited by colchicine. It was demonstrated by immunofluorescence that CB induced the depolymerization of actin filaments and the enhanced assembly of microtubules in cellular processes.