In 75% of granule cells responsive to norepinephrine (NE), micropressure application of NE near the soma of intracellularly impaled granule cells produced membrane depolarizations. Depolarizations were associated with input resistance (Rin) increases; their amplitude increased with membrane depolarization; and had an equilibrium potential of -84 mV. The β-adrenoceptor antagonist timolol blocked the depolarizations. In 38% of NE-sensitive granule cells, NE produced membrane hyperpolarizations. Hyperpolarizations were associated with decreases in Rin; increased with membrane depolarization; and reversed at > -99 mV. In some cells, in which NE was applied at different sites, both depolarizations and hyperpolarizations were observed. Both NE responses were observed in low Ca2+ high Mg2+ medium, suggesting they are due to direct postsynaptic actions of NE on granule cells.
- Granule cell
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