Neuroscience 2003 Abstract
| Presentation Number: | 582.4 |
|---|---|
| Abstract Title: | Differential regulation of endocannabinoid release in the hippocampus . |
| Authors: |
Kim, J.*1,2
; Alger, B. E.1,2
1Neurosci., Univ. of Maryland, Baltimore, MD 2Physiology, Univ. of Maryland, Baltimore, MD |
| Primary Theme and Topics |
Synaptic Transmission and Excitability - Synaptic Transmission -- Postsynaptic mechanisms: Inhibitory |
| Session: |
582. Postsynaptic Mechanisms: Inhibitory II Poster |
| Presentation Time: | Tuesday, November 11, 2003 11:00 AM-12:00 PM |
| Location: | Morial Convention Center - Hall F-I, Board # D90 |
| Keywords: | RETROGRADE, SYNAPTIC TRANSMISSION, LIPID, G PROTEIN |
Endocannabinoids are endogenous compounds that resemble the active ingredient of marijuana and activate the cannabinoid receptor in the brain. In the hippocampus, GABAergic transmission is reduced by endocannabinoids liberated from pyramidal cells in a retrograde way. Endocannabinoids are synthesized and released in a Ca2+-dependent manner, which is called “depolarization-induced suppression of inhibition (DSI)” (Alger, 2002, for review), or in a Ca2+-independent manner upon the activation of muscarinic acetylcholine receptors (mAChRs) (Kim et al., 2002) or metabotropic glutamate receptors (mGluRs) (Varma et al., 2001) on the pyramidal cells. Weak activation of mAChR (Kim et al., 2002) or mGluR (Varma et al., 2001) by low concentration of agonist also enhances DSI. Therefore, there may be three functionally different pathways by which endocannabinoid synthesis and release can be brought about: 1) DSI, 2) enhancement of DSI by weak activation of mAChR or mGluR, and 3) Ca2+-independent release. However, little is known about these cellular pathways. We used whole-cell patch clamp techniques in the CA1 region of rat hippocampal slices, with suppression of inhibitory post synaptic currents as an assay of endocannabinoid release. Different receptor subtypes of mAChR (or mGluR) mediate DSI enhancement and Ca2+-independent release, indicating that the two release mechanisms are separate intracellular processes. Each type of endocannabinoid release can be blocked by different enzyme inhibitors. For example, Ca2+-independent release can be blocked by postsynaptic RHC-80267, a DAG lipase inhibitor, but, interestingly, not by U-73122, a PLC inhibitor. Our results show that there are multiple pathways of endocannabinoid release and they can be modulated separately.
Supported by PHS grants RO1 DA14725, RO1 NS30219
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2003 Neuroscience Meeting Planner. New Orleans, LA: Society for Neuroscience, 2003. Online.
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