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Electrophysiological Methods to Assess Peripheral Pain Block in an Anesthetized Rat
Published on: November 21, 2025
Ifenprodil for prolonged spinal blockades of motor function and nociception in rats
Yu-Wen Chen1, Chong-Chi Chiu2, Jieh-Neng Wang3
1Department of Physical Therapy, College of Health Care, China Medical University, Taichung, Taiwan; Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan.
Background:
The aim of the study was to compare the proposed spinal anesthetic effect of ifenprodil, an a1 adrenergic receptor antagonist, with that of the long-acting local anesthetic bupivacaine.
Methods:
After intrathecally injecting the rats with five different doses of each drug, the dose-response curves of ifenprodil and bupivacaine were constructed to obtain the 50% effective dose (ED50). The spinal blockades of motor function and nociception of ifenprodil were compared with that of bupivacaine.
Results:
We showed that either ifenprodil or bupivacaine produced spinal blockades of motor function and nociception dose-dependently. On the ED50 basis, the potency of ifenprodil (0.42(0.38-0.46) μmol; 0.40(0.36-0.44) μmol) was equal (p>0.05) to that of bupivacaine (0.38(0.36-0.40) μmol; 0.35(0.32-0.38) μmol) in motor function and nociception, respectively. At the equianesthetic doses (ED25, ED50, and ED75), duration produced by ifenprodil was greater than that produced by bupivacaine in motor function and nociception (p<0.05 for the differences). Furthermore, both ifenprodil and bupivacaine showed longer duration of sensory blockade than that of motor blockade (p<0.05 for the differences).
Conclusions:
The resulting data demonstrated that ifenprodil produces a dose-dependent local anesthetic effect in spinal anesthesia. Ifenprodil shows a more sensory-selective duration of action over motor block, whereas the duration of anesthesia is significantly longer with ifenprodil than with bupivacaine.
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