The role of calcium in the repetitive firing of neostriatal neurons.
The Ca++ -dependence of the repetitive firing of neostriatal neurons was studied in an in vitro slice preparation of the rat neostriatum. Neuronal firing was evoked by injecting depolarizing currents of 100-200 ms duration. In normal conditions, the mode of firing was tonic and showed very little adaptation. The frequency-current relation was linear over a wide range of frequencies. The repetitive firing was first enhanced and later suppressed by Co++, Mn++ and Cd++. These effects on the repetitive firing by the Ca++ -channel blockers paralleled the suppression of the slow afterhyperpolarizing potential. The lowering (0.2 mM) of Ca++ had similar effects. In the presence of TEA (up to 10 mM), the cell fired both Na+ and Ca+ action potentials. The results suggest that, as in other CNS neurons of the vertebrate, in neostriatal neurons the slow afterhyperpolarizing potential (AHP) is due to a Ca++ -activated K+ -conductance, and that the AHP plays a crucial role in the repetitive firing of these neurons.
Galarraga
E
E
Department of Physiology, Biophysics and Neurosciences, Centro de Investigación del IPN, México, D.F.
Bargas
J
J
Sierra
A
A
Aceves
J
J
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002413:Cations, Divalent / Q000494:pharmacology; D003342:Corpus Striatum / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D066298:In Vitro Techniques; D051381:Rats; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D002413:Cations, Divalent; D013757:Tetraethylammonium Compounds; D002118:Calcium