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.
Jones
S L
SL
Department of Pharmacology, 764 BMSB, University of Oklahoma Health Sciences Center, P.O. Box 26901, Oklahoma City, OK 73190, USA.
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