Protein kinase A activation increases sodium current magnitude in the electric organ of Sternopygus.
The inactivation kinetics of the Na+ current of the weakly electric fish Sternopygus are modified by treatment with androgens. To determine whether phosphorylation could play a role in this effect, we examined whether activation of protein kinase A by 8 bromo cyclic AMP (8 Br cAMP) altered voltage-dependent properties of the current. Using a two-electrode voltage-clamp procedure, we found no effect of 8 Br cAMP on inactivation kinetics or other voltage-dependent properties of the Na+ current of the electrocytes. However, treatment with 8 Br cAMP did produce a dose-dependent increase in the Na+ current compared with saline controls: 17.6% at 100 microM, 42.4% at 1 mM, and 43.1% at 5 mM. This effect was blocked by 30 microM H89, a PKA inhibitor, indicating that the observed effect was attributable to 8 Br cAMP activation of PKA. We conclude that androgen-induced changes in Na+ current inactivation are not mediated by PKA and suggest that PKA-mediated increases in Na+ current underlie increases in the amplitude of the electric organ discharge observed in social interactions or with changes in water conductance.
McAnelly
L
L
Department of Zoology, University of Texas at Austin 78712, USA.
Zakon
H H
HH
D000818:Animals; D000242:Cyclic AMP / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000494:pharmacology*; D004557:Electric Organ / Q000187:drug effects*; D005399:Fishes; D008564:Membrane Potentials / Q000187:drug effects*; D015222:Sodium Channels / Q000187:drug effects*; D013997:Time Factors
D015222:Sodium Channels; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases