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Enkephalin hyperpolarizes interneurones in the rat hippocampus
1Department of Pharmacology, University of California, San Francisco 94143.
The Journal of Physiology
|April 1, 1988
Summary
Enkephalin, an opiate, selectively targets inhibitory interneurons in the rat hippocampus. This action disinhibits both pyramidal cells and interneurons by activating potassium channels.
Area of Science:
- Neuroscience
- Neuropharmacology
- Cellular Electrophysiology
Background:
- The hippocampus plays a crucial role in learning and memory.
- Inhibitory interneurons regulate neuronal excitability within hippocampal circuits.
- Opiate receptors are known to modulate neuronal activity.
Purpose of the Study:
- To investigate the specific effects of enkephalin on hippocampal CA1 pyramidal cells and interneurons.
- To determine the localization and functional properties of opiate receptors in the hippocampus.
Main Methods:
- Intracellular recordings from CA1 pyramidal cells and identified interneurons in rat hippocampal slices.
- Application of enkephalin and baclofen (GABA(B) receptor agonist).
- Use of the opiate antagonist naloxone to identify opiate receptor involvement.
Main Results:
- Enkephalin hyperpolarized interneurons, likely via increased potassium conductance, an effect blocked by naloxone.
- Enkephalin inhibited glutamate-evoked hyperpolarization in pyramidal cells.
- Enkephalin also reduced inhibitory postsynaptic potentials in interneurons.
- Baclofen-induced hyperpolarization of interneurons was naloxone-resistant.
Conclusions:
- Opiate receptors are selectively located on hippocampal inhibitory interneurons and are coupled to potassium channels.
- Activation of these opiate receptors leads to disinhibition of both pyramidal cells and interneurons.
- This suggests a novel mechanism for opiate-mediated modulation of hippocampal network activity.