Evidence for inhibition of sympathetic preganglionic neurons by bulbospinal epinephrine pathways.
Two selective inhibitors of central epinephrine synthesis, LY 134046 and SKF 64139 (20 mg/kg, i.v.), gradually but markedly enhanced descending intraspinal transmission to sympathetic preganglionic neurons in spinal cats. Enhancement increased linearly to maximum values of 200% and 250%, respectively, at 4.5-5.5 h. Spinal sympathetic reflexes were not enhanced by either drug. The results support the proposal that bulbospinal epinephrine pathways depress the excitability of sympathetic preganglionic neurons by activating postsynaptic alpha 2-adrenergic receptors.
D000320:Adrenergic Fibers / Q000187:drug effects; D000818:Animals; D001339:Autonomic Fibers, Preganglionic / Q000187:drug effects*; D001552:Benzazepines / Q000494:pharmacology*; D002415:Cats; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000037:antagonists & inhibitors*; D005071:Evoked Potentials / Q000187:drug effects; D005728:Ganglia, Sympathetic / Q000187:drug effects*; D007546:Isoquinolines / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism; D010625:Phenylethanolamine N-Methyltransferase / Q000037:antagonists & inhibitors; D012018:Reflex / Q000187:drug effects; D013116:Spinal Cord / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects*; D044005:Tetrahydroisoquinolines
D001552:Benzazepines; D007546:Isoquinolines; D044005:Tetrahydroisoquinolines; C028625:LY 134046; C012153:7,8-dichloro-1,2,3,4-tetrahydroisoquinoline; D010625:Phenylethanolamine N-Methyltransferase; D009638:Norepinephrine; D004837:Epinephrine