Eugenol modifies the excitability of rat sciatic nerve and superior cervical ganglion neurons.
Eugenol is a phenylpropene obtained from the essential oils of plants such as clove and basil which has ample use in dentistry. Eugenol possesses analgesic effects that may be related to the inhibition of voltage-dependent Na+ channels and/or to the activation of TRPV1 receptors or both. In the present study, electrophysiological parameters were taken from the compound action potentials of the isolated rat sciatic nerve and from neurons of the superior cervical ganglion (SCG) impaled with sharp microelectrodes under current-clamp conditions. In the isolated rat sciatic nerve, eugenol inhibited the compound action potential in a concentration-dependent manner. Action potentials recorded from SCG neurons were inhibited by eugenol with an IC(50) of 0.31 mM. At high concentrations (2 mM), during brief applications, eugenol caused significant action potential blockade while it did not interfere with the resting membrane potential or the membrane input resistance. Surprisingly, however, at low eugenol concentrations (0.6 mM), during long time applications, a reversible reduction (by about 50%) in the input membrane resistance was observed, suggesting the possible involvement of a secondary delayed effect of eugenol to reduce neuronal excitability.
Universidade Estadual do Ceará, Instituto Superior de Ciências Biomédicas, Av. Paranjana #1700, Itaperi, 60740-903-Fortaleza, CE, Brazil.
Daniel C A
DC
Moreira-Lobo
Emmanuely D
ED
Linhares-Siqueira
Giovany M P
GM
Cruz
Jader S
JS
Cruz
João L
JL
Carvalho-de-Souza
Saad
S
Lahlou
Andrelina N
AN
Coelho-de-Souza
Roseli
R
Barbosa
Pedro J C
PJ
Magalhães
José H
JH
Leal-Cardoso
D000200:Action Potentials; D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D005054:Eugenol / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D012584:Sciatic Nerve / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D015222:Sodium Channels / Q000502:physiology; D017783:Superior Cervical Ganglion / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D013997:Time Factors
D000700:Analgesics; D015222:Sodium Channels; D005054:Eugenol