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Titolo:
PHE-MET-ARG-PHE-AMIDE ACTIVATES A NOVEL VOLTAGE-DEPENDENT K+ CURRENT THROUGH A LIPOXYGENASE PATHWAY IN MOLLUSCAN NEURONS
Autore:
KITS KS; LODDER JC; VEERMAN MJ;
Indirizzi:
VRIJE UNIV AMSTERDAM,FAC BIOL,NEUROSCI RES INST,GRAD SCH NEUROSCI AMSTERDAM,BOELELAAN 1087 NL-1081 HV AMSTERDAM NETHERLANDS
Titolo Testata:
The Journal of general physiology
fascicolo: 5, volume: 110, anno: 1997,
pagine: 611 - 628
SICI:
0022-1295(1997)110:5<611:PAANVK>2.0.ZU;2-Y
Fonte:
ISI
Lingua:
ENG
Soggetto:
APLYSIA SENSORY NEURONS; DOPAMINE RECEPTOR ACTIVATION; SNAIL LYMNAEA-STAGNALIS; GTP-BINDING PROTEINS; RAT STRIATAL NEURONS; EGG-LAYING BEHAVIOR; POTASSIUM CHANNELS; ARACHIDONIC-ACID; 2ND MESSENGERS; INHIBITORY MODULATION;
Keywords:
PHE-MET-ARG-PHE-AMIDE; S-K CURRENT; POTASSIUM CHANNEL; G-PROTEIN; ARACHIDONIC ACID;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
59
Recensione:
Indirizzi per estratti:
Citazione:
K.S. Kits et al., "PHE-MET-ARG-PHE-AMIDE ACTIVATES A NOVEL VOLTAGE-DEPENDENT K+ CURRENT THROUGH A LIPOXYGENASE PATHWAY IN MOLLUSCAN NEURONS", The Journal of general physiology, 110(5), 1997, pp. 611-628

Abstract

The neuropeptide Phe-Met-Arg-Phe-amide (FMRFa) dose dependently (ED50= 23 nM) activated a K+ current in the peptidergic caudodorsal neurones that regulate egg laying in the mollusc Lymnaea stagnalis. Under standard conditions ([K+](o) = 1.7 mM), only outward current responses occurred. In high K+ salines ([K+](o) = 20 or 57 mM), current reversal occurred close to die theoretical reversal potential for K+. In both salines, no responses were measured below -120 mV. Between -120 mV and the K+ reversal potential, currents were inward with maximal amplitudes at similar to-60 mV. Thus, U-shaped current-voltage relations were obtained, implying that the response is voltage dependent. The conductance depended both on membrane potential and extracellular K+ concentration. The voltage sensitivity was characterized by an e-fold change inconductance per similar to 14 mV at all [K+](o). Since this result was also obtained in nearly symmetrical K+ conditions, it is concluded that channel gating is voltage dependent. In addition, outward rectification occurs in asymmetric K+ concentrations. Onset kinetics of the response were slow (rise time similar to 650 ms at -40 mV). However, when FMRFa was applied while holding the cell at -120 mV, to prevent activation of the current but allow activation of the signal transduction pathway, a subseb quent step to -40 mV revealed a much more rapid current onset. Thus, onset kinetics are largely determined by steps preceding channel activation. With FMRFa applied at -120 mV, the time constant of activation during the subsequent test pulse decreased from similar to 36 ms at -60 mV to similar to 13 ms at -30 mV, confirming that channel opening is voltage dependent. The current inactivated voltage dependently. The rate and degree of inactivation progressively increased from -120 to -50 mV. The current is blocked by internal tetraethylammonium and by bath-applied 4-aminopyridine, tetraethylammonium, Ba2+, and, partially, Cd2+ and Cs+. The response to FMRFa was affected by intracellular GTP gamma S. The response was inhibited by blockers of phospholipase A, and lipoxygenases, but not by a cyclo-oxygenase blocker. Bath-applied arachidonic acid induced a slow outward current and occluded the response to FMRFa. These results suggest that the FMRFa receptor couples via a G-protein to the lipoxygenase pathway of arachidonicacid metabolism. The biophysical and pharmacological properties of this transmitter operated, but voltage-dependent K+ current distinguish it from other receptor-driven K+ currents such as the S-current-and G-protein-dependent inward rectifiers.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 20/09/20 alle ore 19:43:10