Journal of Neurophysiology, Vol 70, Issue 2 541-548, Copyright © 1993 by APS

ARTICLES

Differential modulation of voltage-dependent currents in Hermissenda type B photoreceptors by serotonin

J. Acosta-Urquidi and T. Crow
Department of Neurobiology and Anatomy, University of Texas Medical School, Houston 77225.

1. In identified photoreceptors in the eyes of Hermissenda, serotonin (5-HT) enhances the peak and plateau phases of light-evoked generator potentials and modulates light-dependent and voltage-dependent currents. In addition, electrophysiological and morphological studies indicate that 5-HT may contribute to cellular plasticity detected in the visual system of Hermissenda produced by classical conditioning procedures. With the use of conventional two-electrode voltage-clamp techniques, we examined the effects of 5-HT on three distinct currents recorded across the soma membranes of identified lateral and medial type B photoreceptors in the isolated circumesophageal nervous system. 2. The inward rectifier (Iir), a putative K(+)-dependent conductance, activates in 0-Na artificial seawater at membrane potentials greater than -60 mV, is voltage dependent, noninactivating, and reaches steady-state within 800 ms to 3 s at -100 mV. Bath application of 10(-4) M 5-HT consistently enhanced the magnitude of Iir at all potentials tested (-60 to -100 mV) and, in some cases, allowed expression of Iir, which was not initially detectable before the application of 5-HT. 3. The major component of outward K+ current in type B photoreceptors with IA and IK(Ca) blocked is the delayed rectifier [IK(v)]. 5-HT (10(-4) M) produced both an increase as well as a decrease in the peak amplitude of IK(v) and consistently slowed its inactivation rate and reduced twin-pulse inactivation. 4. A previously identified outward K+ current in type B photoreceptors has properties that are similar to the A current (IA).(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				E. N. Yamoah, S. Levic, J. B. Redell, and T. Crow Inhibition of Conditioned Stimulus Pathway Phosphoprotein 24 Expression Blocks the Reduction in A-Type Transient K+ Current Produced by One-Trial In Vitro Conditioning of Hermissenda J. Neurosci., May 11, 2005; 25(19): 4793 - 4800. [Abstract] [Full Text] [PDF]

				T. Crow Pavlovian Conditioning of Hermissenda: Current Cellular, Molecular, and Circuit Perspectives Learn. Mem., May 1, 2004; 11(3): 229 - 238. [Abstract] [Full Text] [PDF]

				J. T. Birmingham and D. L. Tauck Neuromodulation in invertebrate sensory systems: from biophysics to behavior J. Exp. Biol., October 15, 2003; 206(20): 3541 - 3546. [Abstract] [Full Text] [PDF]

				T. Crow, J. B. Redell, L.-M. Tian, J. Xue-Bian, and P. K. Dash Inhibition of Conditioned Stimulus Pathway Phosphoprotein 24 Expression Blocks the Development of Intermediate-Term Memory in Hermissenda J. Neurosci., April 15, 2003; 23(8): 3415 - 3422. [Abstract] [Full Text] [PDF]

				K. T. Blackwell The Effect of Intensity and Duration on the Light-Induced Sodium and Potassium Currents in the Hermissenda Type B Photoreceptor J. Neurosci., May 15, 2002; 22(10): 4217 - 4228. [Abstract] [Full Text] [PDF]

				C. C. Gandhi and L. D. Matzel Modulation of Presynaptic Action Potential Kinetics Underlies Synaptic Facilitation of Type B Photoreceptors after Associative Conditioning in Hermissenda J. Neurosci., March 1, 2000; 20(5): 2022 - 2035. [Abstract] [Full Text] [PDF]

				E. N. Yamoah, L. Matzel, and T. Crow Expression of Different Types of Inward Rectifier Currents Confers Specificity of Light and Dark Responses in Type A and B Photoreceptors of Hermissenda J. Neurosci., August 15, 1998; 18(16): 6501 - 6511. [Abstract] [Full Text] [PDF]

				T. Crow and V. Siddiqi Time-Dependent Changes in Excitability After One-Trial Conditioning of Hermissenda J Neurophysiol, December 1, 1997; 78(6): 3460 - 3464. [Abstract] [Full Text] [PDF]

				E. N. Yamoah and T. Crow Protein Kinase and G-Protein Regulation of Ca2+ Currents in Hermissenda Photoreceptors by 5-HT and GABA J. Neurosci., August 1, 1996; 16(15): 4799 - 4809. [Abstract] [Full Text] [PDF]