Effect of prazosin on spontaneous sympathetic-cholinergic activity.
Tonic sympathetic-cholinergic electrodermal (sudomotor) activity was measured in intact anesthetized and unanesthetized decerebrate and decerebrate-spinalized cats. Prazosin (3-100 micrograms/kg i.v.) depressed spontaneous electrodermal activity in intact anesthetized cats in a dose-dependent fashion (ED50 4.8 micrograms/kg). Prazosin's action was almost totally abolished by monoamine depletion with reserpine and a synthesis inhibitor. The alpha 2-adrenoceptor blocker, yohimbine (0.5 mg/kg i.v.) also antagonized prazosin-induced sympatho-inhibition. Prazosin reduced tonic sudomotor activity in unanesthetized decerebrate cats in a dose-dependent fashion (ED50 5.5 micrograms/kg i.v.) but was without effect in spinalized preparations. These results support the hypothesis that, in this system, prazosin produces sympatho-inhibition indirectly by means of an alpha 2-adrenoceptor-mediated mechanism, an effect which appears to be prejunctional. It is proposed that prazosin acts at the level of the spinal cord to facilitate ongoing alpha 2-adrenergic inhibition arising from supra-spinal loci.
Koss
M C
MC
Department of Pharmacology, University of Oklahoma Health Sciences Center, Oklahoma City 73190.
Hey
J A
JA
Ito
T
T
D000818:Animals; D015306:Biogenic Monoamines / Q000378:metabolism; D002415:Cats; D003655:Decerebrate State; D005260:Female; D005712:Galvanic Skin Response / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D010275:Parasympathetic Nervous System / Q000187:drug effects*; D011224:Prazosin / Q000494:pharmacology*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism; D013564:Sympathetic Nervous System / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology
D015306:Biogenic Monoamines; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D011224:Prazosin