Journal of Neuroscience, Vol 10, 3960-3969, Copyright © 1990 by Society for Neuroscience
Kainic acid on neostriatal neurons intracellularly recorded in vitro: electrophysiological evidence for differential neuronal sensitivity
P Calabresi, M De Murtas, NB Mercuri and G Bernardi
Clinica Neurologica, 2a Universita di Roma, Italy.
The electrophysiological effects produced by different concentrations of
kainic acid (KA) were studied by utilizing intracellular recordings from
neostriatal slices. In most of the recorded cells (81%), concentrations of
KA ranging between 10 and 300 nM produced reversible and dose-dependent
membrane depolarizations. Higher concentrations of this agonist caused
larger depolarizations and changes of the membrane properties of the
recorded neurons not reversible during the time of recording. In a smaller
percentage (19%) of the recorded cells, 10-100 nM KA did not produce
significant membrane depolarizations; in these neurons, the depolarizations
produced by higher concentrations of KA were small and reversible. The 2
populations of neurons showed similar electrophysiological properties and
did not reveal differential sensitivity to quisqualic acid (QUIS; 10-30
microM) or to NMDA (10-30 microM). Tetrodotoxin (TTX; 1 microM) did not
reduce the depolarizations produced by KA and by NMDA. Low-calcium, cobalt-
containing solutions abolished the effects produced by NMDA, but not the
KA-induced depolarizations. Kynurenic acid (500 microM) significantly
antagonized the depolarizations produced by KA and reduced the changes of
the membrane properties caused by high doses of this agonist. In several
neurons, KA induced bicuculline-sensitive synaptic depolarizing potentials.
Our findings suggest the presence of 2 subpopulations of neostriatal
neurons showing differential postsynaptic sensitivity to KA. The
differential sensitivity of neostriatal neurons to KA might influence the
responses of these cells to glutamatergic cortical inputs and the
degenerative changes observed in neostriatal neurons in some pathological
conditions.
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