Neuroscience 2001 Abstract
| Presentation Number: | 934.8 |
|---|---|
| Abstract Title: | 5-HT<sub>2</sub> RECEPTOR INDUCED SPINAL REFLEX PLASTICITY: LTP AND LTD. |
| Authors: |
Shay, B. L.*1
; Hochman, S.1
1Physiol Dept, Emory Univ Sch Med, Atlanta, GA |
| Primary Theme and Topics |
Motor Systems - Reflex Function |
| Secondary Theme and Topics | Motor Systems<br />- Spinal Cord |
| Session: |
934. Spinal cord: regulation of motoneuron excitability Poster |
| Presentation Time: | Thursday, November 15, 2001 11:00 AM-12:00 PM |
| Location: | Exhibit Hall X-8 |
| Keywords: | serotonin, NMDA, GABA, in vitro |
A long-lasting facilitation of spinal reflexes can be induced by 5-HT2 receptor activation (Machacek et al 1999; SFN). Here we further characterized the expression of long-lasting reflex facilitation (rLTP) as well as identified a long-lasting reflex depression (rLTD).
Electrodes were attached to lumbar roots for stimulation of afferents and recording of ventral root reflexes in the in vitro hemisected rat spinal cord (P2-P13). Stimulation parameters were 500 μA, 50-500 μs and 0.02-0.1 Hz.
Bath applied 5-HT depressed evoked reflexes, then rLTD occurred 5/12 and rLTP in 1/12 cases following wash. DOI (5-HT2 agonist) increased reflex amplitude (4/6) and rLTP was always observed following wash. MK212 (5-HT2C agonist) increased reflex amplitude in 10/14 cases, but following wash both rLTP (7/14) and rLTD (3/14) were observed. Bicuculline (BIC; GABAA antagonist) increased polysynaptic reflexes (PSR;14/14) which was further increased with MK212 (4/5). Comparison of reflex amplitudes before and after removal of MK212 demonstrated rLTP (4/5) or rLTD (1/5) with BIC present, then rLTP (3/5) or rLTD (2/5) in control solution. The BIC increase in PSRs was depressed by APV (NMDA antagonist) (8/9). Even in the presence of APV, MK induced rLTP (5/9) when BIC containing solutions were compared and rLTP was always seen following removal of all drugs (7/7). MK212 evoked reflex plasticity remained in the presence of 5-HT2 receptor antagonists suggesting that continued activation of 5-HT2 receptors is not required for the maintenance of rLTP or rLTD.
We conclude that NMDA and GABAA receptors are not required for rLTP or rLTD. Further, loss of spinal inhibition increases the incidence of rLTP.
Electrodes were attached to lumbar roots for stimulation of afferents and recording of ventral root reflexes in the in vitro hemisected rat spinal cord (P2-P13). Stimulation parameters were 500 μA, 50-500 μs and 0.02-0.1 Hz.
Bath applied 5-HT depressed evoked reflexes, then rLTD occurred 5/12 and rLTP in 1/12 cases following wash. DOI (5-HT2 agonist) increased reflex amplitude (4/6) and rLTP was always observed following wash. MK212 (5-HT2C agonist) increased reflex amplitude in 10/14 cases, but following wash both rLTP (7/14) and rLTD (3/14) were observed. Bicuculline (BIC; GABAA antagonist) increased polysynaptic reflexes (PSR;14/14) which was further increased with MK212 (4/5). Comparison of reflex amplitudes before and after removal of MK212 demonstrated rLTP (4/5) or rLTD (1/5) with BIC present, then rLTP (3/5) or rLTD (2/5) in control solution. The BIC increase in PSRs was depressed by APV (NMDA antagonist) (8/9). Even in the presence of APV, MK induced rLTP (5/9) when BIC containing solutions were compared and rLTP was always seen following removal of all drugs (7/7). MK212 evoked reflex plasticity remained in the presence of 5-HT2 receptor antagonists suggesting that continued activation of 5-HT2 receptors is not required for the maintenance of rLTP or rLTD.
We conclude that NMDA and GABAA receptors are not required for rLTP or rLTD. Further, loss of spinal inhibition increases the incidence of rLTP.
Supported by NINDS #NS40893-01
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2001 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience, 2001. Online.
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