Intrathecal propofol has analgesic effects on inflammation-induced pain in rats.
OBJECTIVE
Propofol is thought to act on gamma-aminobutyric acid receptors, which have some role in pain transmission in the spinal cord. In this study, we examined the effects of intrathecal propofol on acute thermally- or inflammation-induced pain in rats.


METHODS
Lumbar intrathecal catheters were implanted in Male Sprague-Dawley rats. The tail withdrawal response to thermal stimulation (tail flick test) or paw flinching and shaking response by sc formalin injection into the hind paw (formalin test) were tested. Propofol 1000, 300 or 100 microg or saline (control) was administered as 10 microL intrathecally. Motor disturbance and behavioural side effects were also monitored in the rats during the tail flick test. Eight rats were used for each dose in each test.


RESULTS
No analgesic effects were observed in the tail flick test. In the formalin test, 50% of effective doses were 449 mug (95% confidence interval, 80-3180 microg) in phase 1 and 275 microg (146-519 microg) in phase 2. Motor disturbance was observed in one rat with 100 microg and agitation and allodynia were seen in one rat with 300 microg. However, both were reversible in 120 min.


CONCLUSIONS
Intrathecal administration of propofol had analgesic effects on inflammation-induced acute and facilitated pain but not on thermally-induced acute pain. Transient motor and sensory disturbance could not rule out the possibility of neurotoxicity.
Nishiyama
Tomoki
T
Department of Anesthesiology, The University of Tokyo, Faculty of Medicine, Tokyo, Japan. nishit-tky@umin.ac.jp
Matsukawa
Takashi
T
Hanaoka
Kazuo
K
D000700:Analgesics / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D000818:Animals; D004195:Disease Models, Animal; D005557:Formaldehyde / Q000009:adverse effects; D006358:Hot Temperature; D007249:Inflammation / Q000503:physiopathology; D007278:Injections, Spinal; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D010146:Pain / Q000503:physiopathology / Q000517:prevention & control*; D010147:Pain Measurement; D010812:Physical Stimulation; D015742:Propofol / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D011595:Psychomotor Agitation / Q000209:etiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018079:Receptors, GABA / Q000187:drug effects; D013116:Spinal Cord / Q000187:drug effects
D000700:Analgesics; D018079:Receptors, GABA; D005557:Formaldehyde; D015742:Propofol