Neuroscience 2005 Abstract
| Presentation Number: | 563.12 |
|---|---|
| Abstract Title: | Cholinergic neurons in the rat septum express central CB1 cannabinoid receptor mRNA. |
| Authors: |
Diaz-Ruiz, O.*1
; Morales, M. F.1
1Cellular Neurobiology Research Branch, NIDA-IRP, NIH, DHHS, Baltimore, MD |
| Primary Theme and Topics |
Disorders of the Nervous System - Addiction and Drugs of Abuse -- Cannabinoids |
| Session: |
563. Cannabinoids Poster |
| Presentation Time: | Monday, November 14, 2005 4:00 PM-5:00 PM |
| Location: | Washington Convention Center - Hall A-C, Board # UU80 |
| Keywords: | learning and memory, acetylcholine, striatum, drug abuse |
The CB1 receptor mediates brain effects of delta 9-tetrahydrocannabinol (D-9 THC), the major psychoactive constituent of marijuana. D-9 THC and synthetic cannabinoid CB1 receptor agonists reduce in vivo acetylcholine release from hippocampus and frontal cortex (Carta et al., 1998; Gessa et al., 1998; Nava, et al., 2000; Mishima et al., 2002), and inhibit evoked [14C]-acetylcholine release in vitro from cortex and hippocampus (Gifford and Ashby, 1996; Gifford et al., 2000). Despite these findings, CB1 receptors have not to date been detected in cholinergic neurons.
Therefore, we performed double in situ hybridization histochemistry on rat brain sections to identify neurons expressing CB1 mRNA or choline acetyltransferase (ChAT) mRNA (a marker for cholinergic neurons) within the striatum and septum.
As reported by Hohmann and Herkenham (2000), we found that cholinergic neurons in striatum did not express detectable amounts of CB1 mRNA. These data indicate that cholinergic neurons in the striatum lack CB1 receptors. By contrast, we observed that neurons in the septum co-expressed CB1 and ChAT transcripts. Quantitative analysis indicated that about 12% of CB1 expressing neurons in the medial septum and the diagonal band also synthesized ChAT mRNA. This subpopulation of neurons was concentrated in the medial septum. In addition, neurons co-expressing CB1 and ChAT mRNA were identified in only few cholinergic neurons in the diagonal band (5.7% in the horizontal limb, and 4.5% in the vertical limb). In contrast, within the medial septum 11.40% of cholinergic neurons expressed CB1and ChAT mRNA.
In summary, we found that while a subpopulation of septal cholinergic neurons (mostly in the medial septum) expresses CB1 mRNA, this cannabinoid receptor appears to be absent from striatal cholinergic neurons. These findings imply that CB1 receptors are likely to play a role in mediating cholinergic neurotransmission in brain areas that are innervated by septal cholinergic neurons, such as the cortex and hippocampus.
Therefore, we performed double in situ hybridization histochemistry on rat brain sections to identify neurons expressing CB1 mRNA or choline acetyltransferase (ChAT) mRNA (a marker for cholinergic neurons) within the striatum and septum.
As reported by Hohmann and Herkenham (2000), we found that cholinergic neurons in striatum did not express detectable amounts of CB1 mRNA. These data indicate that cholinergic neurons in the striatum lack CB1 receptors. By contrast, we observed that neurons in the septum co-expressed CB1 and ChAT transcripts. Quantitative analysis indicated that about 12% of CB1 expressing neurons in the medial septum and the diagonal band also synthesized ChAT mRNA. This subpopulation of neurons was concentrated in the medial septum. In addition, neurons co-expressing CB1 and ChAT mRNA were identified in only few cholinergic neurons in the diagonal band (5.7% in the horizontal limb, and 4.5% in the vertical limb). In contrast, within the medial septum 11.40% of cholinergic neurons expressed CB1and ChAT mRNA.
In summary, we found that while a subpopulation of septal cholinergic neurons (mostly in the medial septum) expresses CB1 mRNA, this cannabinoid receptor appears to be absent from striatal cholinergic neurons. These findings imply that CB1 receptors are likely to play a role in mediating cholinergic neurotransmission in brain areas that are innervated by septal cholinergic neurons, such as the cortex and hippocampus.
Supported by IRP/NIDA/NIH.
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2005 Neuroscience Meeting Planner. Washington, DC: Society for Neuroscience, 2005. Online.
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