Microiontophoretic application of morphine and naloxone to neurons in hypothalamus of rat.
The present experiments used urethane-anesthetized rats and single cell recording to study the electrophysiological properties of ventromedial hypothalamic (VMH) cells following different doses of morphine and naloxone, applied microiontophoretically. More than 45% of ventromedial hypothalamic units reacted in a dose-response fashion to local application of morphine. In the majority of the ventromedial hypothalamic neurons, naloxone failed to reverse the effects of morphine. Naloxone alone had effects on 37% of the ventromedial hypothalamic units. The ventromedial hypothalamic units exhibited different response patterns from those observed from other CNS sites in response to the microiontophoretic application of morphine and naloxone; this difference is discussed. The present neurophysiological findings support the existence of opiate target sites with multiple opiate receptors within the ventromedial hypothalamus.
D000818:Animals; D004567:Electrodes, Implanted; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D007478:Iontophoresis; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D009270:Naloxone / Q000008:administration & dosage / Q000494:pharmacology*; D009474:Neurons / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D014697:Ventromedial Hypothalamic Nucleus / Q000187:drug effects / Q000502:physiology*
D005971:Glutamates; D009270:Naloxone; D018698:Glutamic Acid; D009020:Morphine