β-Amyloid protein increases the vulnerability of cultured cortical neurons to excitotoxic damage

Information obtained over the past 25 years indicates that the amino acid glutamate functions as a fast excitatory transmitter in the mammalian brain. Studies completed during the last 15 years have also demonstrated that glutamate is a powerful neurotoxin, capable of killing neurons in the central nervous system when its extracellular concentration is sufficiently high. Recent experiments in a variety of preparations have shown that either blockade of synaptic transmission or the specific antagonism of postsynaptic glutamate receptors greatly diminishes the sensitivity of central neurons to hypoxia and ischemia. These experiments suggest that glutamate plays a key role in ischemic brain damage, and that drugs which decrease the accumulation of glutamate or block its postsynaptic effects may be a rational therapy for stroke.

Measurement of lactate dehydrogenase (LDH) activity released to the extracellular bathing media has been found to be a simple yet quantitative method for assessing glutamate mediated central neuronal cell injury in cortical cell culture. Extracellular LDH is both chemically and biologically stable; the magnitude of LDH efflux in the cultures correlates in a linear fashion with the number of neurons damaged by glutamate exposure.