[The effects of isoflurane on the formalin-induced activity in the spinal dorsal horn of transected cat].
Although the formalin test is widely used in rodents, the electrical response to this stimulus and the effect of isoflurane on this response, has not been well understood in cats. We have therefore examined the effect of isoflurane on spinal wide-dynamic-range neuronal activity evoked by a subcutaneous (s.c.) formalin injection in cats. In decerebrate, spinal cord-transected cats (L 1-2), a s.c. injection of formaldehyde solution (0.05 ml; 5%) was performed in the receptive fields of spinal wide-dynamic-range neurons at the hind paw. Isoflurane (1.5%) inhalation was given 20 mins prior to formalin injection or 5 mins after the formalin injection. The formalin injection elicited an immediate and continuous discharge or burst activity in the neurons that lasted at least 90 min. Inhaled isoflurane was found to markedly inhibit this neuronal discharge. At 30 mins after discontinuing of isoflurane, the neuronal activity in both groups recovered to approximately 55% of the control value. These results suggest that formalin injection will reliably produce a continuous burst of neuronal activity in the spinal dorsal horn of cats, and that this activity can be markedly reduced by isoflurane. The ability of isoflurane to inhibit this neuronal response was not temporally related to the formalin injection.
Nagasaka
H
H
Department of Anesthesiology, Saitama Medical School, Saitama.
Taguchi
M
M
Tsuchiya
M
M
Mizumoto
Y
Y
Hori
K
K
Matsumoto
I
I
Hori
T
T
Sato
I
I
D000280:Administration, Inhalation; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002415:Cats; D003655:Decerebrate State; D005071:Evoked Potentials / Q000187:drug effects; D005557:Formaldehyde / Q000494:pharmacology*; D007530:Isoflurane / Q000008:administration & dosage / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects*; D013116:Spinal Cord / Q000187:drug effects* / Q000502:physiology
D018685:Anesthetics, Inhalation; D005557:Formaldehyde; D007530:Isoflurane