Long-term potentiation in an isolated peripheral nerve-spinal cord preparation.
1. Long-lasting increases in synaptic efficacy following repetitive stimulation have been demonstrated at several sites in the CNS, where they are collectively termed long-term potentiation (LTP). LTP is of interest with respect to its presumptive relationship to learning and memory in hippocampus. In the spinal cord in vivo, an LTP-like phenomenon is thought to underlie the allodynia and hyperalgesia that follows some peripheral injuries. 2. We investigated the capacity of the isolated neonatal rat spinal cord to sustain a long-lasting increase in a nociceptive-related slow ventral root potential (sVRP) recorded from a lumbar root after a tetanic train of stimuli to the peripheral cutaneous saphenous nerve. Stimuli were delivered at a low constant (0.02 s-1) frequency during a 30-min control period. A tetanic stimulus train (10 s-1 for 60 s) was then given followed by a resumption of low (0.02 s-1) frequency stimulation. Potentiation was defined as an increase in sVRP area > 2 SD above control mean. 3. Twenty of 20 preparations showed immediate posttetanic potentiation. In 13 of the 20, potentiation was maintained for > or = 1 h after the tetanic stimulus train. 4. Potentiation was dependent on activation of C fibers during the inducing train; stimuli below C-fiber threshold, activating only A fibers, were ineffective. Potentiation was selectively expressed by a long-latency component of the sVRP elicited by stimuli at a strength that evoked both A- and C-fiber responses in the nerve.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000502:physiology; D007858:Learning / Q000502:physiology; D017774:Long-Term Potentiation / Q000502:physiology*; D008568:Memory / Q000502:physiology; D009020:Morphine / Q000494:pharmacology; D017933:Peripheral Nervous System / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000502:physiology*; D013997:Time Factors
D009020:Morphine