Intrathecal pre-administration of fentanyl effectively suppresses formalin evoked c-Fos expression in spinal cord of rat.

Abstract

PURPOSE:

To investigate whether the timing of intrathecal administration of the opioid analgesic fentanyl, alters noxious stimulus-evoked neuronal activity in the rat spinal cord.

METHODS:

A 5% formalin solution was used as the noxious stimulant. For the pretreatment group, a dose of 0.001 to 0.5 microg of fentanyl was injected intrathecally ten minutes prior to formalin injection. Early and late post-treatment groups received 0.01 to 0.5 microg fentanyl, five and 60 min after formalin injection respectively. The effect of fentanyl was confirmed with naloxone. The level of c-Fos expression was determined in each treatment group to indicate neuronal activity.

RESULTS:

Pretreatment and early post-treatment groups showed suppression of c-Fos activity compared to the vehicle (P <0.01). The late post-treatment group showed no difference in c-Fos activity compared to the vehicle (P=NS). Pretreatment with fentanyl showed the most profound suppression of c-Fos expression (P <0.01). In addition, pretreatment injection showed a greater suppression of c-Fos activity in the deep (14.6% of control) compared to the superficial laminae (32.7% of control; P <0.01), whereas the early post-treatment group showed a universal decrease in c-Fos activity (49.2% of control in laminae I and II, 50.4% of control in laminae III and IV and 51.8% of control in laminae V and VI). Naloxone reversed the action of fentanyl on c-Fos activity.

CONCLUSION:

Inasmuch as: 1) c-Fos expression can be equated with behavioural changes; 2) injection of formalin is an appropriate model of surgical trauma; and 3) animal data can be transports to humans, these results suggest that fentanyl would be an effective pre-emptive analgesic.

• Authors: T Nakamura, M Takasaki
• Journal: Canadian journal of anaesthesia = Journal canadien d'anesthesie (Can J Anaesth) Vol. 48 Issue 10 Pg. 993-9 (Nov 2001) ISSN: 0832-610X [Print] United States
• PMID: 11698319 (Publication Type: Journal Article)

Chemical References

• Analgesics, Opioid
• Proto-Oncogene Proteins c-fos
• Formaldehyde
• Fentanyl

Topics

• Analgesia (methods)
• Analgesics, Opioid (pharmacology)
• Animals
• Fentanyl (administration & dosage, pharmacology)
• Formaldehyde (pharmacology)
• Immunohistochemistry
• Male
• Premedication
• Proto-Oncogene Proteins c-fos (analysis)
• Rats
• Rats, Sprague-Dawley
• Spinal Cord (chemistry, drug effects, physiology)