Effects of opiate-like peptides, morphine, and naloxone in the photosensitive baboon, Papio papio.
The effects of intracerebroventricular (i.c.v.) or systemic injections of Met- or Leu-enkephalin, beta-endorphin, FK 33.824 (D-Ala2, MePhe4, Met(O5)-ol-enkephalin) and of morphine and naloxone have been studied in baboons, Papio papio, which spontaneously show photically induced epileptic responses. Animals were chronically implanted with epidural or deep recording electrodes and a cannula in one lateral ventricle, and tested whilst seated in a primate chair. In some animals the natural syndrome was enhanced by the prior administration of DL-allylglycine, 100--200 mg/kg, i.v. Met- or Leu-enkephalin, 1--10 mg, i.c.v., did not lead to any manifest focal or generalized seizure discharges. Nor did it lead to any consistent enhancement or reduction of photically induced myoclonic responses (as tested 5--10 min after injection). beta-Endorphin, 0.1--0.5 mg, i.c.v., did not enhance or impair photically induced myoclonic responses. FK 33.824, 0.1--0.5 mg, i.c.v., depressed respiration and slowed EEG background rhythms for 9--15 h. This was associated with a loss of myoclonic responses to photic stimulation. These effects were reversed for 20--40 min following the injection of naloxone, 1 mg/kg i.m. A depression of respiration and a slowing of EEG rhythms was seen beginning 5--20 min after FK 33.824, 2 or 4 mg/kg, i.v. The higher dose also abolished photically induced myoclonic responses. Naloxone, 1 mg/kg, definitively reversed these effects. Morphine, 5--10 mg i.c.v., tended to increase the latency to onset of generalized myoclonus during photic stimulation. Myoclonic responses were delayed or diminished after morphine, 5 mg/kg, i.m. Naloxone, 1--2 mg/kg i.m., reversed this effect. Naloxone, 0.2--5.0 mg/kg i.m., alone, did not significantly modify photically induced myoclonus, either in animals of low or high initial responsiveness, or in those pretreated with allylglycine.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002540:Cerebral Cortex / Q000187:drug effects; D004569:Electroencephalography; D004723:Endorphins / Q000494:pharmacology*; D004745:Enkephalins / Q000494:pharmacology*; D005071:Evoked Potentials / Q000187:drug effects; D000882:Haplorhini; D007273:Injections, Intramuscular; D007276:Injections, Intraventricular; D009020:Morphine / Q000494:pharmacology*; D009207:Myoclonus / Q000503:physiopathology*; D009270:Naloxone / Q000494:pharmacology*; D010215:Papio; D010775:Photic Stimulation; D011957:Receptors, Opioid / Q000187:drug effects; D012119:Respiration / Q000187:drug effects; D012640:Seizures / Q000503:physiopathology*; D013787:Thalamic Nuclei / Q000187:drug effects
D004723:Endorphins; D004745:Enkephalins; D011957:Receptors, Opioid; D009270:Naloxone; D009020:Morphine