Excitatory Role of the Hyperpolarization-Activated Inward Current in Phasic and Tonic Firing of Rat Supraoptic Neurons

• DOI: 10.1523/jneurosci.20-13-04855.2000
• Publication Date: 2018-04-04T19:20:19Z
• Authors: Masoud Ghamari-La...; Charles W. Bourque
• Keywords: Hyperpolarization; Tonic (physiology); Bursting; Supraoptic nucleus; Current clamp

The properties and functional roles of the hyperpolarization-activated inward current (I(H)) in magnocellular neurosecretory cells (MNCs) were investigated during sharp microelectrode recordings from supraoptic neurons superfused explants rat hypothalamus. Under clamp, voltage responses to hyperpolarizing pulses featured depolarizing sags that abolished by I(H) blocker ZD 7288. subtraction steps recorded absence presence 7288 was used investigate I(H). Current-voltage analysis revealed steady-state amplitude increases with hyperpolarization, half-maximal activation underlying conductance occurring at -78 mV. time course monoexponential constants (100-800 msec) decreasing hyperpolarization. effects on slow (tau, approximately 15 min), irreversible, 1.8 micrometer. When tested continuously active MNCs, application 30-60 micrometer caused a significant reduction firing rate. In phasically drug decreased burst duration intraburst frequency an increase interburst intervals. These accompanied small hyperpolarization membrane potential. contrast, had no effect spike duration, calcium-dependent afterpotentials, or frequencies amplitudes spontaneous synaptic potentials. results confirm MNCs nucleus suggest this provides excitatory drive contributes phasic tonic firing.