The Effects Coronary Artery Occlusion On The Pain-sensitive Neurons In Nucleus Parafascicularis And The Modulation Of Opioid-receptor

This study investigated the changes in the action potentials ofsingle cells among the pain-sensitive neurons of nucleus parafascicularis(Pf) in thalami before and after occlusion of the anterior descending branch of the left coronary artery and determined the effects intravenours opioid-receptor agonist and antagonist on the neurons discharges. Male SD rats weighing 260g-300g were operated under urethane anesthesia and local anesthesia. Only the cells responding to somatic nociceptive stimulation were further examined. The recording were made using single-barrel glass electrode for 20 seconds every 5 minutes before and after the coronary artery occlusion (CAO). The recording cells were divided into 3 groups as following: in group I no interruption was applied; in group II 0.01mg/kg fentanyl citrate were intravenous administrated at the point of 15 minutes after CAO; in group III 0.04mg/kg ketamins were intravenous administrated at the point of 15 minutes after intravenous fentanyl. The results showed that 36 out of 63 neurons studied (57.14%) did not show changes in the discharge frequency following the CAO while the frequency of cell discharge of the other 27 neurons was markedly increased immediately following the CAO and during the 60 minutes after the CAO. Meanwhile, intravenous fentanyl 0.01mg/kg can completely inhibit the increased frequency of cell discharge within 10 minutes and intravenous ketamins 0.04mg/kg can also totally antagonize prescribed role of fentanyl. These results indicated that (1) CAO can increase the frequency of the pain-sensitive neurons discharge in nucleus parafascicularis. (2) Opioid-receptor play a critical role in transmission of acute rnyocardial ischemia evoked pain.