ROLE OF PRESYNAPTIC A-TYPE POTASSIUM CURRENT IN REGULATING SYNAPTIC TRANSMISSION IN THE LAMPREY SPINAL CORD.
Research field:Central nervous system
Authors:Hess D, Lamotte dŽIncamps B, El Manira A
Address of presenting
author:		Karolinska Institutet
Nobel Institut for Neurophysiology
Dept. of Neuroscience
171 77 Stockholm, Sweden
E-mail:dietmar.hess@neuro.ki.se
Phone:46-8-728-7345
Fax:46-8-349-544
Text of abstract Introduction
Potassium channels play an important role in regulating neuronal activity by controlling their excitability and synaptic transmission. We have recently characterized a high voltage activated A-type potassium current (IA). This current shows rapid activation and inactivation and is specifically blocked by catechol (100 ”M). The biophysical properties of the lamprey IA correspond to those of the cloned mammalian Kv3.4 channels.In this study we have examined the role of IA in regulating synaptic transmission in the lamprey spinal cord.

Methods
In this study, we have used the in vitro preparation of the lamprey spinal cord. Paired intracellular recordings were made from presynaptic reticulospinal axons and postsynaptic neurons. The effect of the specific blocker of the IA was examined both on the presynaptic action potential and the postsynaptic EPSPs. Whole cell patch clamp recordings were made from isolated spinal neurons in culture to test if catechol has any postsynaptic effect on membrane depolarizations simulating EPSPs.

Results
Blockade of IA by catechol (100 ”M) significantly increased the amplitude of the chemical component of the monosynaptic EPSPs without affecting the electrical component. The increase in the amplitude of the EPSP was associated with an increase in the width of the presynaptic action potentials, indicating that catechol mediates its effect on synaptic transmission via presynaptic mechanisms. Catechol had no effect on the EPSP waveforms in dissociated patch clamped neurons, that were generated from EPSP recordings made in the intact spinal cord.

Conclusions
These results indicate that IA are located on presynaptic axons and control the duration of the action potential and the amount of calcium influx, and thereby transmitter release.

References

Keywords:potassium channels, presynaptic, symaptic transmission, model, lamprey

Created 2000-05-03