Persistent sodium current is a target for cAMP-induced neuronal plasticity in a state-setting modulatory interneuron.
We have identified a TTX-resistant low-threshold persistent inward sodium current in the cerebral giant cells (CGCs) of Lymnaea, an important state-setting modulatory cell type of molluscan feeding networks. This current has slow voltage-dependent activation and de-activation kinetics, ultra-slow inactivation kinetics and fast de-inactivation kinetics. It activates at approximately -90 mV, peaks at approximately -30 mV, reverses at approximately +35 mV and does not show full voltage-dependent inactivation even at positive voltage steps. Lithium-sodium replacement experiments indicate that the persistent sodium current makes a significant contribution to the CGC membrane potential. Injection of cyclic adenosine monophosphate (cAMP) into the CGC cell body produces a large increase in the persistent sodium current that lasts for several hours. cAMP injection also leads to increased bursting, a significant decrease in the resistance and a significant depolarization of the soma membrane, indicating that cAMP-dependent mechanisms induce prolonged neuronal plasticity in the CGCs. Our observations provide the first link between cAMP-mediated modulation of a TTX-resistant persistent sodium current and prolonged neuronal plasticity in an identified modulatory cell type that plays an important role in behavioral state setting.
Nikitin
E S
ES
School of Life Sciences, Department of Biology and Environmental Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK.
Kiss
T
T
Staras
K
K
O'shea
M
M
Benjamin
P R
PR
Kemenes
G
G
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000494:pharmacology*; D007395:Interneurons / Q000187:drug effects / Q000502:physiology*; D008195:Lymnaea / Q000502:physiology*; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000378:metabolism*
D012964:Sodium; D000242:Cyclic AMP