Electrophysiological recordings and calcium measurements in striatal large aspiny interneurons in response to combined O 2 /glucose deprivation. J. Neurophysiol. 81: 2508Neurophysiol. 81: -2516Neurophysiol. 81: , 1999. The effects of combined O 2 /glucose deprivation were investigated on large aspiny (LA) interneurons recorded from a striatal slice preparation by means of simultaneous electrophysiological and optical recordings. LA interneurons were visually identified and impaled with sharp

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... roelectrodes loaded with the calcium (Ca 2ϩ )-sensitive dye bis-fura-2. These cells showed the morphological, electrophysiological, and pharmacological features of large striatal cholinergic interneurons. O 2 /glucose deprivation induced a membrane hyperpolarization coupled to a concomitant increase in intracellular Ca 2ϩ concentration ([Ca 2ϩ ] i ). Interestingly, this [Ca 2ϩ ] i elevation was more pronounced in dendritic branches rather than in the somatic region. The O 2 /glucose-deprivation-induced membrane hyperpolarization reversed its polarity at the potassium (K ϩ ) equilibrium potential. Both membrane hyperpolarization and [Ca 2ϩ ] i rise were unaffected by TTX or by a combination of ionotropic glutamate receptors antagonists, D-2-amino-5-phosphonovaleric acid and 6cyano-7-nitroquinoxaline-2,3-dione. Sulfonylurea glibenclamide, a blocker of ATP-sensitive K ϩ channels, markedly reduced the O 2 / glucose-deprivation-induced membrane hyperpolarization but failed to prevent the rise in [Ca 2ϩ ] i . Likewise, charybdotoxin, a large K ϩchannel (BK) inhibitor, abolished the membrane hyperpolarization but did not produce detectable changes of [Ca 2ϩ ] i elevation. A combination of high-voltage-activated Ca 2ϩ channel blockers significantly reduced both the membrane hyperpolarization and the rise in [Ca 2ϩ ] i . In a set of experiments performed without dye in the recording electrode, either intracellular bis-(o-aminophenoxy)-N,N,NЈ,NЈ-tetraacetic acid or external barium abolished the membrane hyperpolarization induced by O 2 /glucose deprivation. The hyperpolarizing effect on membrane potential was mimicked by oxotremorine, an M2-like muscarinic receptor agonist, and by baclofen, a GABA B receptor agonist. However, this membrane hyperpolarization was not coupled to an increase but rather to a decrease of the basal [Ca 2ϩ ] i . Furthermore glibenclamide did not reduce the oxotremorine-and baclofeninduced membrane hyperpolarization. In conclusion, the present results suggest that in striatal LA cells, O 2 /glucose deprivation activates a membrane hyperpolarization that does not involve ligand-gated K ϩ conductances but is sensitive to barium, glibenclamide, and charybdotoxin. The increase in [Ca 2ϩ ] i is partially due to influx through voltage-gated high-voltage-activated Ca 2ϩ channels.