Electrographic studies of the effects of RP 60180, a novel kappa agonist, on the photosensitive baboon Papio papio.

1. The authors describe here the effects of intravenous administration of RP 60180, a novel kappa agonist, on conscious baboons of the species Papio papio, which spontaneously present photically induced epileptic responses. 2. Animals (n = 2) were chronically implanted with epidural recording electrodes and tested whilst seated in a primate chair. The electrocorticogram (ECoG) and electrocardiogram (ECG) were recorded during a control period of at least 30 minutes before the injection of RP 60180 (1 to 4.5 mg/kg i.v.) and immediately afterwards. 3. Qualitatively, up to the dose of 4.5 mg/kg i.v., RP 60180 did not modify ECoG background in term of paroxysmal activity in comparison with that observed during the control period. It did not cause any manifest focal or generalized seizure discharges, nor did it consistently enhance or reduce photically induced myoclonic responses. 4. From the dose of 1 mg/kg i.v., RP 60180 slowed ECG frequency. This effect, which lasted for about 30 minutes post-injection, was most often seen at the higher doses. 5. In another set of experiments, one baboon received the kappa agonist U-50488 (a benzacetamide derivative of spiradoline) at 1 and 3 mg/kg i.v. U-50488, at 3 and to a lesser degree at 1 mg/kg i.v., induced paroxysmal bursts of slow wave ECoG activity and a slowing of the ECG. These effects lasted about 1 hour post-drug administration. During this period, we observed spontaneous vocalization, as if the animal were complaining, as well as shaking.