title: Synaptosomal release of newly-synthetized or recently accumulated amino acids. Differential effects of kainic acid on naturally occurring excitatory amino acids and on [d-(3)H]aspartate.
abstract: Kainic acid, a powerful neuroexcitant and neurotoxin, stimulates the release of naturally occurring excitatory amino acids, l-glutamate and l-aspartate, from hippocampal synaptosomes. The release stimulation affects in a similar way both the general pool of the two amino acids and the fraction of l-glutamate and l-aspartate, newly-synthetized from precursors or recently accumulated through the high-affinity uptake mechanism. Kainic acid exerts its stimulatory action on the basal release of the two amino acids as well as on the high K(+)-stimulated release of l-glutamate. Kainic acid has, however, different effects on the release of exogenously accumulated [d-(3)H]aspartate. In particular, the high K(+)-stimulated release of this false transmitter is strongly inhibited by 1 mM kainic acid. The present data confirm the presynaptic action of kainic acid on the general as well as on the recently-formed pools of naturally occurring excitatory amino acids. At the same time, our results suggest that [d-(3)H]aspartate is not a reliable substitute for l-glutamate and l-aspartate, in release studies and that the radioactivity released after preloading with [d-(3)H]aspartate does not necessarily reflect the release of naturally occurring excitatory amino acids.
authors.affiliation: Laboratory of General Physiology, Institute of Comparative Anatomy, University of Bologna, 40126 Bologna, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Virgili
authors.forename: A
authors.initials: A
authors.lastname: Poli
authors.forename: A
authors.initials: A
authors.lastname: Contestabile
authors.forename: P
authors.initials: P
authors.lastname: Migani
authors.forename: O
authors.initials: O
authors.lastname: Barnabei