[The effects of intrathecally administered baclofen on somato-sympathetic reflex potentials].
We investigated the antinociceptive effect of intrathecally administered S(-)-baclofen and R (+)-baclofen in cats using somato-sympathetic reflex potentials derived from lumbar sympathetic ganglion by stimulation of the femoral nerve. S(-)-baclofen 10 mg maximally reduced both A reflex potential and C reflex potential to 65.3% and 83.7% of control values, respectively, 1 minute after the administration, but these changes were not significant. The inhibition of A reflex potential at this dosage was greater than that of blood pressure and heart rate induced by the same dosage of S(-)-baclofen. While, R(+)-baclofen 1 mg maximally inhibited A reflex potential to 48.6% of control value 20 minutes after the administration, and this change was significant (P < 0.05). The inhibition of A reflex potential was greater than that of blood pressure and heart rate induced by the same dosage of R(+)-baclofen. This dosage of baclofen reduced C reflex potential to 66.4% of control value 10 minutes after the administration. The degree of reduction of A and C reflex potentials induced by 1 mg of R(+)-baclofen was higher in comparison with that induced by 10 mg of S(-)-baclofen. These reduction of A and C reflex potentials were reversed by 1 to 1.5 mg of intrathecally administered saclofen. These results indicate that R(+)-baclofen has higher potency than S(-)-baclofen and suggest that S(-)-baclofen and R(+)-baclofen show antinociceptive effect by intrathecal administration. On the other hand, it is possible that these two drugs exert antinociceptive effect via A delta fiber.
Saeki
Shigeru
S
Department of Anesthesiology, Nihon University School of Medicine, Tokyo 173-8610.
Tamura
Mariko
M
Iida
Ryoji
R
Nakamura
Takashi
T
Kobayashi
Terukazu
T
Ogawa
Setsuro
S
D000700:Analgesics; D000818:Animals; D001418:Baclofen / Q000008:administration & dosage / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D007278:Injections, Spinal; D009125:Muscle Relaxants, Central / Q000008:administration & dosage / Q000494:pharmacology*; D012018:Reflex / Q000187:drug effects*
D000700:Analgesics; D009125:Muscle Relaxants, Central; D001418:Baclofen