PT - JOURNAL ARTICLE AU - Sacha A. Malin AU - Jeanne M. Nerbonne TI - Elimination of the Fast Transient in Superior Cervical Ganglion Neurons with Expression of KV4.2W362F: Molecular Dissection of<em>I</em><sub>A</sub> AID - 10.1523/JNEUROSCI.20-14-05191.2000 DP - 2000 Jul 15 TA - The Journal of Neuroscience PG - 5191--5199 VI - 20 IP - 14 4099 - http://www.jneurosci.org/content/20/14/5191.short 4100 - http://www.jneurosci.org/content/20/14/5191.full SO - J. Neurosci.2000 Jul 15; 20 AB - Electrophysiological and molecular studies have revealed considerable heterogeneity in voltage-gated K+currents and in the subunits that underlie these channels in mammalian neurons. At present, however, the relationship between native K+ currents and cloned subunits is poorly understood. In the experiments here, a molecular genetic approach was exploited to define the molecular correlate of the fast transient outward K+ current,IAf, in sympathetic neurons and to explore the functional role of IAf in shaping action potential waveforms and controlling repetitive firing patterns. Using the biolistic gene gun, cDNAs encoding a dominant negative mutant Kv4.2 α-subunit (Kv4.2W362F) and enhanced green fluorescent protein (EGFP) were introduced into rat sympathetic neuronsin vitro. Whole-cell voltage-clamp recordings obtained from EGFP-positive cells revealed that IAfis selectively eliminated in cells expressing Kv4.2W362F, demonstrating that Kv4 α-subunits underlie IAf in sympathetic neurons. In addition, IAfdensity is increased significantly in cells overexpressing wild-type Kv4.2. In cells expressing Kv4.2W362F, input resistances are increased and (current) thresholds for action potential generation are decreased, demonstrating that IAf plays a pivotal role in regulating excitability. Expression of Kv4.2W362F and elimination ofIAf also alters the distribution of repetitive firing patterns observed in response to a prolonged injection of depolarizing current. The wild-type superior cervical ganglion is composed of phasic, adapting, and tonic firing neurons. Elimination of IAf increases the percentage of adapting cells by shifting phasic cells to the adapting firing pattern, and increased IAf density reduces the number of adapting cells.