L-Type Calcium Channels are Modified in Rat Hippocampus by Short-Term Experimental Ischemia

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Abstract
Increasing evidence suggests a role for calcium ions in the pathophysiology of ischemic brain damage. The major mechanism allowing calcium entry from the extracellular compartment is the opening of voltage-operated calcium channels. In this line, we have explored the hypothesis that the characteristics of central L-type voltage-dependent calcium channels, labeled by the dihydropyridine ligand 3H-PN 200-110, may be modified by experimental ischemia. The results show that short-term mild ischemia, produced in the rat by 1 h of right carotid ligation, induces an increase in the number of 3H-PN 200-110 binding sites in the hippocampus ipsilateral to the side of carotid occlusion, accompanied by an increase in the dissociation constant value, whereas no changes in the kinetic parameters of the binding were observed in the other areas examined, i.e., the cortex and the striatum. The changes in hippocampus are transient: 96 h after the occlusion, binding parameters return to the control range. The modifications of the binding characteristics in the hippocampus may be related to alterations of Ca2+ fluxes through L-type calcium channels.