Calcium channel modulators modify K opioid-induced inhibition of C-fiber-evoked spinal reflexes in rat.
The role of L-type Ca2+ channels on the kappa opioid-induced depression of spinal afferent transmission was assessed in spinalized rats, through recording of the C-fiber-evoked spinal flexor reflex. Six successive i.t. doses of the K agonist U-50,488H produced a dose-dependent decrease of the C-reflex duration (ID50: 25.7 nmol), the log dose-response relationship being shifted to left by pretreatment with 5 mg/kg i.v. of the calcium channel blocker verapamil, or to right by pretreatment with .25 mg/kg i.v. of the calcium channel agonist Bay K8644. Verapamil and Bay K8644, administered i.v. after U-50,488H i.t., respectively potentiated or antagonized the depressor effect of the K ligand on the reflex. The results point to a role for Ca2+ availability as a factor involved in depression of afferent nociceptive transmission by K opioids at the spinal cord.
Hernández
A
A
Unit on Neurophysiology and Biophysics, Institute of Nutrition and Food Technology, University of Chile, Santiago.
Contreras
E
E
Paeile
C
C
Pérez
H
H
Pelissier
T
T
Quijada
L
L
Soto-Moyano
R
R
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects* / Q000502:physiology; D007278:Injections, Spinal; D009412:Nerve Fibers / Q000187:drug effects* / Q000502:physiology; D010146:Pain / Q000503:physiopathology*; D011759:Pyrrolidines / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D017473:Receptors, Opioid, kappa / Q000187:drug effects* / Q000502:physiology; D012018:Reflex / Q000187:drug effects*; D013116:Spinal Cord / Q000187:drug effects* / Q000503:physiopathology; D009435:Synaptic Transmission / Q000187:drug effects; D014700:Verapamil / Q000494:pharmacology
D000700:Analgesics; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D011759:Pyrrolidines; D017473:Receptors, Opioid, kappa; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D014700:Verapamil; D002118:Calcium