CALCIUM-DEPENDENT RELEASE OF D-[H-3]ASPARTATE EVOKED BY SELECTIVE ELECTRICAL-STIMULATION OF EXCITATORY AFFERENT-FIBERS TO HIPPOCAMPAL PYRAMIDAL CELLS INVITRO

Selective electrical stimulation of CA1 excitatory afferent fibres in the stratum radiatum of a transverse slice of the hippocampus released d-[3H]aspartate in a stimulus dependent manner, d-aspartate being used to mimic endogenous l-glutamate. The release fulfilled several of the requirements for neurotransmitter identification in as much as it was Ca2+-dependent and specific. Neither [3H]γ-aminobutyrate nor l-[3H]leucine were released in response to stimulation. The stimulus dependent release of d-[3H]aspartate could also be demonstrated in an isolated preparation of the hippocampal slice containing the CA3/CA1 region, but devoid of the area dentata and subiculum. A cut carefully placed in the isolated CA3/CA1 slice dividing all CA1 afferents coursing through the stratum radiatum, without sectioning the pyramidal layer nor the stratum oriens/alveus, abolished the stimulus-evoked release of d-[3H]aspartate. The results, together with previous work, favour l-glutamate as the neurotransmitter of the Schaffer collaterals of the CA3 pyramidal cells. © 1979.