DESCENDING SEROTONERGIC SYSTEMS PROTECT SPINAL CORD NEURONS FROM THE DELETERIOUS EFFECTS OF NOCICEPTIVE STIMULATION. E.D.Crown*; J.W.Grau. Dept Psychol, Texas A&M Univ, College Station, TX, USA
We have developed a paradigm to assess spinal cord function that relies on instrumental learning. Rats are tested by applying shock to one hindleg whenever that limb is extended. In spinally transected rats, exposure to response-contingent shock causes an increase in flexion duration that decreases net shock exposure. Rats given shock independent of leg position (noncontingent shock) do not exhibit an increase in flexion duration. Just 6 min of noncontingent shock to the leg or the tail undermines spinal cord plasticity for 48 hrs. Previously, we have demonstrated that rats given shock prior to spinalization do not exhibit a behavioral deficit (Grau & Crown, Soc Neuro Abs, 28, 2001). In addition, we reported last year that rats given a dorsolateral funiculus (DLF) lesion prior to spinalization failed to learn, suggesting that descending projections from the brainstem are responsible for the protective effect. Given that a portion of the projections that comprise the DLF are serotonergic in nature, the current experiments explored the role of this system in the protective effect observed in previous studies. Experiment 1 determined that intrathecal application of either serotonin (5HT) or the 5HT 1A receptor agonist, 8-OH DPAT, protected spinal cord neurons from the disruptive effects of intermittent tailshock. Neither the 5HT 2 agonist, DOI, nor the 5HT 3 agonist, quipazine, had any effect. Experiment 2 showed that antagonizing the 5HT 1A receptor using WAY 100635 had the same effect as a DLF lesion, allowing 6 min of intermittent tailshock to disrupt spinal cord plasticity.
Supported by: MH60157 to JWG & RCM.
Citation: E.D.Crown, J.W.Grau. DESCENDING SEROTONERGIC SYSTEMS PROTECT SPINAL CORD NEURONS FROM THE DELETERIOUS EFFECTS OF NOCICEPTIVE STIMULATION.. Program No. 363.3. 2002 Abstract Viewer/Itinerary Planner. Washington, DC: Society for Neuroscience, 2002. CD-ROM.