Effects of noradrenergic agonists on superficial dorsal horn neurons in the cat spinal cord.
The objectives of the present study were to determine the effects of iontophoretically-applied noradrenergic agonists on the unit activity of physiologically characterized superficial dorsal horn neurons in the barbiturate-anesthetized cat spinal cord, and to determine if a relationship exists between the effects produced by these agents and neuron modality. The effects of norepinephrine (NE), clonidine (CLON, a selective alpha2-agonist) and phenylephrine (PE, a selective alpha1-agonist) on spontaneous and D,L-homocysteic acid (DLH)-evoked unit activity were examined for 68 superficial dorsal horn neurons. Iontophoretically applied NE inhibited (40% of the cells examined) and excited (39% of the cells examined) unit activity. Mixed effects (i.e., inhibition and excitation) on unit activity also were observed (10% of the cells examined), and NE had no effect on the unit activity of some cells (11% of the cells examined). Excitation was the predominant effect produced by CLON (62% of the cells examined); however, inhibition (19% of the cells examined), mixed effects (5% of the cells examined), and no effects on unit activity (14% of the cells examined) also were observed. Iontophoretically applied PE inhibited (46% of the cells examined) and excited (36% of the cells examined) unit activity. Mixed effects on unit activity also were observed (4% of the cells examined), and PE had no effect on the unit activity of some cells (14% of the cells examined). Whether NE, CLON or PE exerted excitatory or inhibitory effects on unit activity did not depend on neuron modality.
Department of Pharmacology, 764 BMSB, University of Oklahoma Health Sciences Center, P.O. Box 26901, Oklahoma City, OK 73190, USA.
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D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D002415:Cats; D003000:Clonidine / Q000494:pharmacology; D004553:Electric Conductivity; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D009638:Norepinephrine / Q000819:agonists* / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects*
D000316:Adrenergic alpha-Agonists; D010656:Phenylephrine; D003000:Clonidine; D009638:Norepinephrine