Intracellular Recordings from Pineal Cells in Tissue Culture: Membrane Properties and Response to Norepinephrine

摘要

The interaction between sympathetic nerve terminals and pinealocytes has been among the most thoroughly studied neurotransmitter-effector relationships in the nervous system. It was one of the earliest, and still remains one of the few, system wherein the link between agonist-receptor binding and subsequent functional biochemical changes were thoroughly characterized. There have been few studies of the intracellular electrophysiological correlates to the well characterized biochemical effects of pineal Beta-adrenoreceptor activation. Nothing is known about the intrinsic membrane properties of pinealocytes. Proper interpretation of neurotransmitter effects requires that the underlying membrane conductances be known. Membrane properties and responsiveness to norepinephrine were studied in pinealocytes in tissue culture using both conventional and whole-cell patch-clamp techniques. Action potentials could be recorded in normal and tetrodotoxin-containing saline. Both outward and inward rectification were prominent. Under voltage-clamp, depolarizing voltage steps evoked time-dependent outward currents showing no inactivation over time. Hyperpolarizing steps evoked slowly developing inward currents which did not inactivate. If the holding potential was sufficiently negative, depolarizing steps also elicited a transient outward current. Iontophoresis of norepinephrine produced a hyperpolarization in 30% of cells tested. Keywords: Electrophysiology.