Opiates inhibit pedunculopontine neurones in guinea pig brainstem slices.
Intracellular recordings were obtained from pedunculopontine neurones in guinea-pig brainstem slices. These cells were characterized by a broad action potential, an A-like conductance and fired spontaneously in a regular manner. These neurones were inhibited by bath-application of both carbachol and serotonine at concentrations of 10(-4) M. Opioid peptides induced a dose-dependent hyperpolarization and a reduction in the spontaneous firing. These latter effects could be blocked by the opiate antagonist naloxone and were direct as they persisted in presence of tetrodotoxine or high magnesium/low calcium-containing salines. They were mediated by an opiate receptor of the mu type since they were obtained with the mu-preferring enkephalin analogues FK 33-824 and DAGO, but neither with the delta nor the kappa analogues such as DPLPE or U-50,488.
Serafin
M
M
Département de Physiologie, Centre Médical Universitaire, Geneva, Switzerland.
Khateb
A
A
Mühlethaler
M
M
D000818:Animals; D001933:Brain Stem / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004745:Enkephalins / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009294:Narcotics / Q000494:pharmacology*; D009433:Neural Inhibition; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D011149:Pons / Q000166:cytology / Q000187:drug effects* / Q000502:physiology
D004745:Enkephalins; D009294:Narcotics; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin