5-Hydroxytryptamine-induced outward currents mediated via 5-HT1A receptorsin neurons of the rat dorsolateral septal nucleus

Effects of 5-hydroxytryptamine (5-HT) on neurons of the rat dorsolateral se ptal nucleus (DLSN) were examined by intracellular and whole-cell patch-cla mp recording techniques. An outward current was induced by 5-HT (1-100 mu M ) in a concentration-dependent manner. The EC50 for 5-HT was 4.8 mu M. Also , 8-OH-DPAT (10-100 mu M) produced the outward current an EC50 of 17 mu M. Amplitudes of the outward currents produced by 5-HT (100 mu M) and 8-OH-DPA T (100 mu M) were 117 +/- 4 (n = 6) and 58 +/- 8 pA (n = 6), respectively. Fluvoxamine (200 nM), a specific serotonin re-uptake inhibitor, enhanced th e 5-HT (1 mu M) - induced outward current: the EC50 for 5-HT was 0.5 mu M i n the presence of fluvoxamine (200 nM). L-694 247 (100 mu M) and CP 93129 ( 100 mu M) also produced outward currents with amplitudes of 33 +/- 3 (n = 4 ) and 18 +/- 5 pA (n = 4), respectively in DLSN neurons. DOI (100 mu M) and RS 67333 (100 mu M) did not produce outward currents. NAN 190 shifted, in a parallel manner, the concentration-response relationship of 5-HT to the r ight. The Lineweaver-Burk plot of the concentration-response curve showed t hat NAN-190 depressed the 5-HT-induced current in a competitive manner. The current-voltage relationship indicates that the 5-HT-induced current rever sed polarity at a potential close to the equilibrium potential of K+. Ba2(100 mu M-1 mM) partially depressed the outward current produced by 5-HT. T hese results suggest that 5-HT induces multiple K+ currents via 5-HT1A rece ptors in DLSN neurons. (C) 2000 Elsevier Science Ireland Ltd. All rights re served.