Ž . Molecular Brain Research 74 1999 55–68 www.elsevier.comrlocaterbres Research report Developmental changes in the expression of Shaker- and Shab-related K q channels in neurons of the rat trigeminal ganglion Gerald Seifert ) , Elena Kuprijanova, Min Zhou 1 , Christian Steinhauser ¨ Experimental Neurobiology, Neurosurgery, UniÕersity of Bonn, Sigmund-Freud-Str. 25, 53105 Bonn, Germany Accepted 24 August 1999 Abstract q Ž . We have investigated properties of voltage-gated K channels in neurons of the pre- and postnatal rat trigeminal ganglion TG . To correlate functional data with information on gene expression of Shaker- and Shab-related channels in these pseudo-unipolar neurons, the Ž . Ž . patch-clamp technique was combined with the single-cell reverse transcription-polymerase chain reaction RT-PCR . A majority 80% of prenatal TG neurons possessed only sustained delayed rectifier currents with half-maximal current inactivation at y30 mV. In the Ž . postnatal cells, steady-state inactivation of sustained currents occurred at more negative voltages half-maximal inactivation at y58 mV . About 65% of the postnatal cells displayed a transient outward component in addition to the sustained currents. With increasing age, the Ž . sensitivity of sustained currents to 4-aminopyridine 4-AP decreased significantly. The Shaker channel toxins, a-dendrotoxin and Ž . Ž . agitoxin-2 50 and 10 nM , were much less effective. Discrimination between both stages with tetraethylammonium chloride 5 mM was not possible since the currents were reduced generally by about 50%. After recording, the cell content was harvested and single-cell RT-PCR was performed to compare K q current properties and mRNA expression within the same cell. Most cells simultaneously expressed several different Shaker- and Shab-like transcripts. At postnatal day 14, the frequency of cells carrying transcripts encoding Kv1.1 decreased. Detailed analysis revealed a higher 4-AP sensitivity of TG neurons expressing Kv1.1 transcripts. q 1999 Elsevier Science B.V. All rights reserved. Keywords: Patch-clamp; Single-cell RT-PCR; Kv1; Kv2; Pharmacology 1. Introduction Ž . Voltage-gated potassium channels Kv channels are ubiquitously distributed in the mammalian nervous system and are composed of various a-subunits. They serve many functions in cell physiology, including stabilization of resting potential, determination of neuronal spike fre- quency and regulation of proliferation and differentiation. At least 18 genes belonging to the four subfamilies Kv1– Kv4 have, to date, been identified, corresponding to four Drosophila potassium channel genes Shaker , Shab, Shaw, w x and Shal, respectively 22,32 . The large number of iso- forms indicates a considerable diversity in the composition and functioning of these channels. Additional variability of Kv channel structure and function is produced by coex- pression of ‘auxiliary’ a- or b-subunits. The composition ) Corresponding author. Fax: q49-228-287-9121; e-mail: gese@mailer.meb.uni-bonn.de 1 Min Zhou is now in the Division of Neurosurgery, Albany Medical College, Albany, NY 12208, USA. and stoichiometry of native Kv channels are, however, largely unknown and the question of the temporal changes in the expression of distinct Kv subunits accounting for changes during K q current development in vivo is unan- swered. Ž . The mammalian trigeminal ganglion TG is relatively large, and is reliably discernible and accessible even at early stages of ontogenesis. Rat TG neurons are born w x between embryonic days 9.5 and 14.5 57 . Despite the controversy concerning the presence or absence of synap- w x tic inputs in TG neurons 26,59 , their perikarya could play a role in the modulation of afferent signal transduction w x 33 . Using sharp electrodes, the latter authors provided the first analysis of K q currents in adult TG neurons of guinea pig in situ. These investigations have revealed K q outward currents with unusual pharmacological properties that were speculated to contribute to prevention of excessive spike activity during pathophysiological conditions such as w x trigeminal neuralgia 45 . To learn more about these currents, we extended the analysis by comparing K q current properties in TG neu- 0169-328Xr99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0169-328X 99 00268-5