The effects of low doses of morphine on the activity of dopamine-containing cells and on behavior.
Intravenous (IV) administration of 10 ug/kg of morphine sulfate increased the firing rate of Type A dopamine neurons but decreased the extracellular activity of Type B dopamine cells in the substantia nigra pars compacta and ventral tegmental area of anesthetized male rats. The morphine-produced increase in Type A cells was antagonized by 0.10 mg/kg of naloxone, whereas the suppression of B cells was blocked only by pretreatment with 5.0 mg/kg of naloxone. This same low dose of morphine (IV) also produced increased locomotor activity in awake male rats within 10 min of administration.
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000502:physiology*; D004298:Dopamine / Q000502:physiology*; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects*; D009270:Naloxone / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains
D009270:Naloxone; D009020:Morphine; D004298:Dopamine