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Opioid inhibition in locus coeruleus
R A Travagli1, T V Dunwiddie, J T Williams
1Vollum Institute, Oregon Health Sciences University, Portland 97201, USA.
Journal of Neurophysiology
|August 1, 1995
Summary
Opioid inhibition of locus coeruleus (LC) neurons involves electrotonic coupling, not just potassium conductance. This coupling synchronizes noradrenaline release in the brain, persisting into adulthood.
Area of Science:
- Neuroscience
- Neuropharmacology
- Cellular Electrophysiology
Background:
- Opioid inhibition of locus coeruleus (LC) neurons is typically linked to hyperpolarization via increased potassium conductance.
- However, observed outward currents at potentials more negative than potassium equilibrium potential suggested alternative mechanisms.
Purpose of the Study:
- To investigate the mechanism of opioid-induced currents in LC neurons.
- To explore the role of electrotonic coupling in LC neuron activity and opioid response.
Main Methods:
- Whole-cell and intracellular recordings from LC neurons in brain slices.
- Local iontophoresis of [Met]5enkephalin (ME) to assess current responses.
- Pharmacological manipulation of ion conductances (potassium, sodium) and electrotonic coupling (carbenoxolone).
Main Results:
- Opioid application induced outward currents with complex reversal potentials, partially dependent on potassium and sodium conductances.
- Electrotonic coupling between LC neurons was observed in adult animals, persisting from neonatal stages.
- Carbenoxolone blocked electrotonic coupling and shifted opioid current reversal potentials, implicating coupling in the opioid response.
Conclusions:
- LC neurons are electrotonically coupled, a phenomenon that persists into adulthood.
- This electrotonic coupling influences opioid-induced currents and mediates synchronous noradrenaline regulation in widespread brain areas.