[Involvement of opioid peptides in corticofugal modulation of pain]

The effect of opioid peptides on corticofugal modulation of nociceptive response in thalamic ventrobasal nucleus (VB) produced by cortical sensorimotor area II (Sm II) was observed. Single unit activities of VB neurons were extracellularly recorded by glass microelectrodes. The results showed that the nociceptive responses of VB neurons were attenuated at 0-7.5 minutes after stimulating Sm II (n = 14, P < 0.05). The inhibitory effect of stimulation of Sm II was reduced after ventriculer microinjection of 20ul of naloxone (n = 9), while marked inhibition was shown at 0-2.5 minutes after stimulating Sm II in the saline control group (n = 9, P < 0.05). There was a statistical difference at 0-2.5 minutes after stimulating Sm II between the two groups (P < 0.05). These studies suggest that opioid peptides might be involved in corticofugal modulation of pain.