Actions of norepinephrine and isoflurane on inhibitory synaptic transmission in adult rat spinal cord substantia gelatinosa neurons.
Volatile inhaled anesthetics and nitrous oxide (N2O) are often used together in clinical practice to produce analgesia. Because the analgesic effect of N2O is, at least in part, mediated by norepinephrine (NE) release in the spinal cord, we examined the interaction between isoflurane (ISO) and NE in the adult rat spinal cord with respect to central nociceptive information processing. The effects of clinically relevant concentrations of ISO (1 MAC) and NE (20 microM) on spontaneous inhibitory transmission in substantia gelatinosa (SG) neurons were examined using the blind whole-cell patch-clamp method. ISO prolonged the decay time and increased the total charge transfer of spontaneous inhibitory postsynaptic currents. NE increased the frequency and mean amplitude of inhibitory postsynaptic currents and the charge transfer as well. Coapplication of both drugs led to an additive increase of the charge transfer and frequent temporal summation of inhibitory postsynaptic currents. We conclude that both ISO and NE enhance the inhibitory synaptic transmission in the rat SG neurons and their interaction is additive, suggesting that ISO may add to the analgesic action of N2O at the spinal cord dorsal horn level.
Georgiev
Stefan K
SK
Division of Anesthesiology, Niigata University Graduate School of Medical and Dental Sciences, Japan.
Wakai
Ayako
A
Kohno
Tatsuro
T
Yamakura
Tomohiro
T
Baba
Hiroshi
H
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D066298:In Vitro Techniques; D007530:Isoflurane / Q000494:pharmacology*; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects* / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013376:Substantia Gelatinosa / Q000187:drug effects* / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects* / Q000502:physiology
D007530:Isoflurane; D009638:Norepinephrine