Involvement of postsynaptic alpha 1- and alpha 2-adrenoceptors in the flexor reflex activity in the spinal rats.
Clonidine (0.2 mg/kg i.v.) and St 587 (1 mg/kg i.v.), selective agonists of alpha 2- and alpha 1-adrenoceptors, respectively, increased the flexor reflex amplitude in the spinal rat. Yohimbine and rauwolscine, alpha 2-adrenoceptor antagonists, inhibited dose-dependently the effect of clonidine but not of St 587. However, prazosin and clozapine, alpha 1-adrenoceptor antagonists, diminished the action of both agonists in a dose-dependent manner. After central chemosympathectomy caused by 6-OH-DA or DSP-4 the response to clonidine did not differ from that in the sham-operated animals. In 6-OH-DA treated rats yohimbine (1 mg/kg i.v.) antagonized the effect of clonidine to the same extent as it did in unlesioned animals. It is concluded that the results are functional evidence that alpha 1- and alpha 2-adrenoceptors are present in the rat spinal cord, and stimulation of each receptor increases flexor reflex activity.
D000818:Animals; D003000:Clonidine / Q000031:analogs & derivatives / Q000494:pharmacology; D003024:Clozapine / Q000494:pharmacology; D003655:Decerebrate State; D008297:Male; D009638:Norepinephrine / Q000378:metabolism; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D012018:Reflex / Q000187:drug effects; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; C030655:St 587; D015016:Yohimbine; D003024:Clozapine; D003000:Clonidine; D009638:Norepinephrine; D011224:Prazosin