Long-term potentiation of polysynaptic responses in layer V of the sensorimotor cortex induced by theta-patterned tetanization in the awake rat.
Although the neocortex in awake, adult animals is resistant to the induction of long-term potentiation (LTP), synaptic potentiation may be enhanced by rhythmic patterns of activation that evoke short- term synaptic facilitation effects. The effectiveness of stimulation patterned after the theta (4-12 Hz) EEG rhythm for the induction of LTP of sensorimotor cortex responses to corpus callosum stimulation was assessed in vivo by inducing LTP using either high- frequency (300 Hz) trains or paired trains delivered at a 100 ms (10 Hz) interval. High-frequency trains caused a reduction of the early field potential component, reflecting a potentiation of direct layer V activation, and a potentiation of the late component, reflecting enhanced polysynaptic activation in layer V. Paired trains resulted in a much larger potentiation of polysynaptic responses than was observed following 300 Hz trains. To determine if short-term facilitation effects contributed to the enhanced LTP induction by theta-patterned trains, facilitation effects induced by the trains were challenged with NMDA receptor antagonists. NMDA-receptor antagonism reduced responses to single pulses, and also reduced facilitated responses evoked by theta-patterned stimulation. The effectiveness of theta-patterned stimulation for the induction of LTP of layer V polysynaptic responses is therefore likely due to frequency-dependent synaptic facilitation effects that enhance NMDA receptor activation.
Werk
Christine M
CM
Center for Studies in Behavioral Neurobiology, Department of Psychology, Concordia University, Montréal, Québec, Canada H3G 1M8.
Chapman
C Andrew
CA
D000818:Animals; D017774:Long-Term Potentiation / Q000502:physiology*; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology*; D013569:Synapses / Q000502:physiology*; D013826:Theta Rhythm / Q000379:methods*; D014851:Wakefulness / Q000502:physiology
D016194:Receptors, N-Methyl-D-Aspartate