Chronic morphine exposure impairs short-term synaptic depression of geniculo-cortical visual pathway in vivo.
Chronic morphine exposure can induce addiction and affect synaptic plasticity, but the underlying neuronal mechanisms remain unknown. Two forms of short-term synaptic depression (paired-pulse depression (PPD) and frequency depression) were investigated in vivo in the geniculo-cortical visual pathway of morphine-treated and saline-treated (as control) adult rats. Acute exposure to morphine had no effect on paired-pulse synaptic depression and 10-40 Hz induced frequency synaptic depression. However, chronic morphine exposure reduced markedly the paired-pulse depression and frequency depression at 40 Hz. The effect of chronic morphine exposure on short-term synaptic plasticity in the geniculo-cortical visual pathway was sensitization given that morphine re-exposure further significantly reduced the short-term synaptic depression. Interestingly, the further reduction in short-term synaptic depression due to re-exposure of morphine was recovered to normal (control) levels at 3 to 6h after morphine re-exposure. These findings suggest that chronic morphine treatment could significantly degrade the short-term synaptic plasticity of geniculo-cortical visual pathway.
Wang
Hao
H
Hefei National Laboratory for Physical Sciences at Microscale and School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, PR China.
Wei
Haiyang
H
Chen
Bo
B
Zhou
Yifeng
Y
D000200:Action Potentials / Q000187:drug effects / Q000528:radiation effects; D000818:Animals; D004307:Dose-Response Relationship, Radiation; D004334:Drug Administration Schedule; D004558:Electric Stimulation / Q000379:methods; D066298:In Vitro Techniques; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects*; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009294:Narcotics / Q000494:pharmacology*; D009433:Neural Inhibition / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000187:drug effects*; D013997:Time Factors; D014795:Visual Pathways / Q000166:cytology* / Q000187:drug effects
D009294:Narcotics; D009020:Morphine