title: Alpha adrenoceptor modulation of the jaw-opening reflex.
abstract: In the present study, the nature, role and location of the alpha-adrenoceptors, modulating the tooth pulp stimulation (TPS)-evoked jaw-opening reflex (JOR), was investigated. Clonidine, a lipophilic alpha 2-adrenoceptor agonist, rapidly, reversibly and significantly elevated the threshold of the digastric electromyogram (dEMG) evoked by tooth pulp stimulation which was antagonized by yohimbine or piperoxane (two alpha 2-adrenoceptor antagonists) but not by prazosin (an alpha 1-adrenoceptor antagonist). 4-Hydroxyclonidine and ST-91 non lipophilic alpha 2 adrenoceptor agonists, were ineffective on the tooth pulp stimulation-evoked threshold of the digastric electromyogram. Clonidine was ineffective upon digastric muscle stimulation (DMS)-evoked threshold of the digastric electromyogram of the curarized digastricus and mylohyoid (motor) nerve stimulation (MNS)-evoked digastric EMG. It is concluded that modulation by clonidine of the tooth pulp stimulation-evoked jaw-opening reflex is devoid of a peripheral efferent component and that such modulation is predominantly expressed through interactions with centrally located alpha 2 adrenoceptors.
authors.forename: A L
authors.initials: AL
authors.lastname: Curtis
authors.forename: J
authors.initials: J
authors.lastname: Marwah
mesh_terms: D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D003782:Dental Pulp / Q000502:physiology; D004056:Differential Threshold; D004558:Electric Stimulation; D004576:Electromyography / Q000379:methods; D007568:Jaw / Q000502:physiology*; D008297:Male; D009619:Nociceptors / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects
chemical_list: D011942:Receptors, Adrenergic, alpha; D003000:Clonidine