Differential distribution of diacylglycerol lipase-alpha and N-acylphosphatidylethanolamine-hydrolyzing phospholipase D immunoreactivity in the superficial spinal dorsal horn of rodents
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1
University of Debrecen, Department of Anatomy, Histology and Embryology, Hungary
It is generally accepted that the endocannabinoid system acting as a retrograde modulator of synaptic transmission plays important roles in pain processing at various levels of the central nervous system including the superficial spinal dorsal horn. Although it is extensively documented that cannabinoid 1 receptors are strongly expressed in the spinal dorsal horn, constituents of spinal neural circuits that can synthesize endocannabinoid ligands are not so well characterized. Thus, using pre- and post-embedding immunocytochemical methods, we investigated the distribution of diacylglycerol lipase-alpha (DGL-α) and N-acylphosphatidylethanolamine-hydrolyzing phospholipase D (NAPE-PLD), enzymes responsible for the synthesis of the major endocannabinoid ligands, 2-arachidonoylglycerol (2-AG) and anandamide, respectively. Postsynaptic dendrites showed strong immunoreactivity for both enzymes, but positive labeling was revealed only occasionally in axon terminals. The dendritic localization of DGL-α and NAPE-PLD showed a remarkably different distribution. A substantial proportion of DGL-α immunorective puncta established close appositions with axon terminals of nociceptive primary afferents and putative excitatory spinal neurons. In ultrastructural studies, these puncta were found to be attached to dendritic membranes in close vicinity to asymmetric synaptic contacts. In contrast to this, NAPE-PLD immunoreactive puncta were mostly revealed on dendritic membrane compartments further away from synapses. In addition, both enzymes showed a remarkably strong labeling on astrocytes and microglial cells. Our results suggest that both neurons and glial cells can synthesize and release 2-AG and anandamide in the superficial spinal dorsal horn. 2-AG can be released by postsynaptic dendritic compartments adjacent to asymmetric synapses. It is also likely that 2-AG and anandamide can also be released from dendritic and glial compartments that are not associated with synapses.
Conference:
IBRO International Workshop 2010, Pécs, Hungary, 21 Jan - 23 Jan, 2010.
Presentation Type:
Poster Presentation
Topic:
Sensory and motor systems
Citation:
Hegyi
Z,
Holló
K,
Kiss
G,
Mackie
K and
Antal
M
(2010). Differential distribution of diacylglycerol lipase-alpha and N-acylphosphatidylethanolamine-hydrolyzing phospholipase D immunoreactivity in the superficial spinal dorsal horn of rodents.
Front. Neurosci.
Conference Abstract:
IBRO International Workshop 2010.
doi: 10.3389/conf.fnins.2010.10.00221
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Received:
04 May 2010;
Published Online:
04 May 2010.
*
Correspondence:
Zoltán Hegyi, University of Debrecen, Department of Anatomy, Histology and Embryology, Debrecen, Hungary, hegyiz@chondron.anat.dote.hu