INDUCTION OF CALPAIN-MEDIATED SPECTRIN FRAGMENTS BY PATHOGENIC TREATMENTS IN LONG-TERM HIPPOCAMPAL SLICES

The use of cultured hippocampal slices for studies of calpain-mediated pathogenesis was investigated. Breakdown products (BDPs), which resul t from proteolysis of spectrin by calpain I, were assayed with BDP-spe cific antibodies developed against peptide sequences on either side of the calpain cleavage site. The antibodies recognized either amino- or carboxy-terminal BDPs (147-kD BDPN and 152-kD BDPC, respectively). Va rious pathogenic manipulations, including trimethyltin, certain snake venoms and agonists for excitatory amino acid receptors, were found to cause rapid and pronounced increases in the proteolytic fragments. Th ese effects were selective, i.e., chemicals or toxins directed at nong lutamatergic neurons had little effect on BDP concentrations. Transien t accumulations of spectrin fragments were obtained with brief applica tions of N-methyl-D-aspartate; longer infusions resulted in lasting in creases. Results similar to these have been observed in vivo with isch emic episodes of varying duration. Agonists of the lpha-amino-3-hydrox y-5-methylisoxazole-4-propionic acid subclass of glutamate receptors p roduced significant increases in spectrin proteolysis; however, prolon ged exposure of the slices to centrally active drugs that enhance the currents passed by the receptors did not. The sensitivity, selectivity and temporal properties of the proteolytic response support the idea that cultured slices can be used to analyze the events leading to and following from calpain activation in the adult brain.