RESUMEN
The influence of testosterone on the postnatal development of reflex electromyographic (EMG) jaw muscle activity evoked by injection of mustard oil (MO) into the temporomandibular joint region and the later recurrence of this EMG activity after intravenous injection of naloxone, was studied in male rats. MO-evoked EMG activity in the contralateral digastric muscle and naloxone-induced recurrence of this EMG activity were fully developed in intact, 8-week-old rats. Castration at 4 weeks of age inhibited the development of the contralateral MO-evoked EMG activity, but did not influence the naloxone-induced recurrence. Contralateral MO-evoked responses were observed in 8-week-old castrated rats if they received testosterone replacement therapy beginning at 4 weeks of age. These data suggest that testosterone is required for the development of a contralateral nociceptive reflex in the digastric muscle of male rats.
Asunto(s)
Músculo Esquelético/fisiología , Articulación Temporomandibular/efectos de los fármacos , Testosterona/fisiología , Envejecimiento/fisiología , Análisis de Varianza , Animales , Área Bajo la Curva , Castración , Electromiografía , Lateralidad Funcional , Maxilares , Masculino , Músculo Masetero/efectos de los fármacos , Músculo Masetero/fisiología , Músculo Esquelético/efectos de los fármacos , Planta de la Mostaza , Naloxona/farmacología , Antagonistas de Narcóticos/farmacología , Dolor , Extractos Vegetales/farmacología , Aceites de Plantas , Ratas , Reflejo , Articulación Temporomandibular/fisiología , Factores de TiempoRESUMEN
The effect of intrathecal administration of the 5-HT(3) receptor agonist 2-methyl-5-hydroxytryptamine (2m-5HT) on jaw muscle activity evoked by mustard oil (MO) injection into the temporomandibular joint of anesthetized rats was examined. One microgram or 100 microg of 2m-5HT significantly enhanced or suppressed jaw muscle responses, respectively. Pre-administration of tropisetron, a 5-HT(3) receptor antagonist, attenuated the effect of 2m-5HT. These results indicate that activation of 5-HT(3) receptors can modulate trigeminal nociceptive responses.