Male rats require testosterone to develop contralateral digastric muscle activity in response to noxious stimulation of the temporomandibular joint.
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.
Seo
Kenji
K
Division of Dental Anesthesiology, Department of Tissue Regeneration and Reconstruction, Niigata University Graduate School of Medical and Dental Sciences, Course for Oral Life Science, Niigata 951-8514, Japan. seo@dent.niigata-u.ac.jp
Fujiwara
Naoshi
N
Cairns
Brian E
BE
Someya
Genji
G
D000375:Aging / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D019540:Area Under Curve; D002369:Castration; D004576:Electromyography; D007839:Functional Laterality; D007568:Jaw; D008297:Male; D008406:Masseter Muscle / Q000187:drug effects / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology*; D009149:Mustard Plant; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D010146:Pain; D010936:Plant Extracts / Q000494:pharmacology; D010938:Plant Oils; D051381:Rats; D012018:Reflex; D013704:Temporomandibular Joint / Q000187:drug effects* / Q000502:physiology; D013739:Testosterone / Q000502:physiology*; D013997:Time Factors
D009292:Narcotic Antagonists; D010936:Plant Extracts; D010938:Plant Oils; D009270:Naloxone; D013739:Testosterone; C027793:mustard oil