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.
Long-term intrinsic enhanced excitability is a characteristic of cellular plasticity and learning-dependent modifications in the activity of neural networks. The regulation of voltage-dependent K+ channels by phosphorylation/dephosphorylation and their localization is proposed to be important in the control of cellular plasticity. One-trial conditioning in Hermissenda results in enhanced excitability in sensory neurons, type B photoreceptors, of the conditioned stimulus pathway. Conditioning also regulates the phosphorylation of conditioned stimulus pathway phosphoprotein 24 (Csp24), a cytoskeletal-related protein containing multiple beta-thymosin-like domains. Recently, it was shown that the downregulation of Csp24 expression mediated by an antisense oligonucleotide blocked the development of enhanced excitability in identified type B photoreceptors after one-trial conditioning without affecting short-term excitability. Here, we show using whole-cell patch recordings that one-trial in vitro conditioning applied to isolated photoreceptors produces a significant reduction in the amplitude of the A-type transient K+ current (I(A)) detected 1.5-16 h after conditioning. One-trial conditioning produced a depolarized shift in the steady-state activation curve of I(A) without altering the inactivation curve. The conditioning-dependent reduction in I(A) was blocked by preincubation of the photoreceptors with Csp antisense oligonucleotide. These results provide an important link between Csp24, a cytoskeletal protein, and regulation of voltage-gated ion channels associated with intrinsic enhanced excitability underlying pavlovian conditioning.
Yamoah
Ebenezer N
EN
Center for Neuroscience, Department of Otolaryngology, University of California, Davis, California 95616, USA.
Levic
Snezana
S
Redell
John B
JB
Crow
Terry
T
D000704:Analysis of Variance; D000818:Animals; D003213:Conditioning, Psychological; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D049870:Hermissenda / Q000502:physiology*; D066298:In Vitro Techniques; D007266:Inhibition, Psychological; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D008564:Membrane Potentials / Q000502:physiology / Q000528:radiation effects; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D018408:Patch-Clamp Techniques / Q000379:methods; D010750:Phosphoproteins / Q000502:physiology*; D017956:Photoreceptor Cells, Invertebrate; D015221:Potassium Channels / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D013997:Time Factors
D020319:Oligodeoxyribonucleotides, Antisense; D010750:Phosphoproteins; D015221:Potassium Channels