Direct inhibition by opioid peptides of neurones located in the ventromedial nucleus of the guinea pig hypothalamus
|Published in||Brain Research. 1988, vol. 450, no. 1-2, p. 124-130|
|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.|
|Keywords||Action Potentials/drug effects — Animals — Enkephalin, Ala(2)-MePhe(4)-Gly(5)- — Enkephalin, D-Penicillamine (2,5)- — Enkephalins/ pharmacology — Guinea Pigs — Male — Membrane Potentials/drug effects — Neural Inhibition/ drug effects — Ventromedial Hypothalamic Nucleus/ drug effects/physiology|
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