Effects of high-frequency synaptic stimulation on glumate receptor binding studied with a modified in vitro...

Slices of the field CA1 minus the stratum moleculare were prepared from the rat hippocampus and maintained in an in vitro recording chamber. The physiological properties of these "minislices" were similar to those reported for non-dissected hippocampal slices. Slices receiving various patterns of electrical stimulation through multiple electrodes were subsequently homogenized and crude membrane fractions prepared; the binding of [3H]glutamate was measured by a rapid filtration assay. Binding in membranes prepared from control slices exhibited kinetic properties and sensitivities to pharmacological and ionic manipulations which were comparable to those found in previous studies using conventional fractionation and assay techniques. Brief bursts of high-frequency stimulation increased [3H]glutamate binding compared to non-stimulated controls in 3 separate experiments. Stimulation at low frequency or at high frequency in low calcium medium did not produce this effect. In addition to suggesting that glutamate binding sites are regulated by patterns of afferent activity, these findings indicate that the minislice preparation should be of general utility in relating synaptic physiology to synaptic chemistry.