<b>Expression of pERK-LI cells in the trigeminal spinal nucleus caudalis following propofol administration in rats</b>

Abstract

Propofol (PRO) is frequently used as the reliable sedative agent in clinic situation because it is safe and easy to control the depth of sedative level. PRO, however, has weak analgesic action even causing acute pain sensation during intravenous infusion. For the clinical use of sedatives, the invasive action such as pain should be relieved. It is very important to know underlying mechanisms of the weak analgesic action of propofol in order to improve clinical use of PRO. We studied the phosphorylated Extracellular Signal-regulated Kinase (pERK) expression in the trigeminal spinal nucleus and upper cervical nociceptive neurons to clarify the central mechanism of the enhancement of trigeminal transmission. We observed that a large number of pERK-LI cells were expressed in Vi/Vc zone, middle Vc and Vc-C2 zone immediately after the large amount of propofol injection. The number of pERK-LI cells was increased following increase in the amount of PRO administration. We also observed that the expression of pERK-LI cells was depressed after the lidocaine injection before PRO injection. The present findings suggest that PRO has a strong ability to enhance nociceptive neuronal activity in the trigeminal region through the primary afferent nociceptors innervated in the cervical vein, resulting in the central sensitization of the trigeminal nociceptive pathways during infusion.