title: Direct inhibition by opioid peptides of neurones located in the ventromedial nucleus of the guinea pig hypothalamus.
abstract: In slices of guinea pig brain, intracellular recordings were obtained from neurones of the ventromedial nucleus of the hypothalamus (VMH). [D-Ala2,NMePhe4,Gly-ol5]enkephalin (DAGO), an agonist selective for mu-opioid receptors, caused an inhibition of spontaneous firing activity and a membrane hyperpolarization. This effect was reversible, concentration-dependent and could be blocked by naloxone. DAGO directly inhibited VMH neurones since its effect persisted when the slice was perifused with a solution that blocks synaptic transmission. The hyperpolarization induced by DAGO was associated with a marked decrease in membrane input resistance and it was reversed in polarity at membrane potentials 30-40 mV more negative than the resting potential. A chloride current did not contribute to the hyperpolarization brought about by DAGO. We conclude that DAGO inhibits VMH neurones, probably by opening membrane potassium channels.
authors.affiliation: Department of Physiology, University Medical Center, Genève, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Charpak
authors.forename: M
authors.initials: M
authors.lastname: Dubois-Dauphin
authors.forename: M
authors.initials: M
authors.lastname: Raggenbass
authors.forename: J J
authors.initials: JJ
authors.lastname: Dreifuss
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000494:pharmacology*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009433:Neural Inhibition / Q000187:drug effects*; D014697:Ventromedial Hypothalamic Nucleus / Q000187:drug effects* / Q000502:physiology
chemical_list: D004745:Enkephalins; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-