[Effects of microiontophoretically applied U-50488 on the spontaneous discharges, of respiration related units (RRUs) in the region of nucleus ambiguus or rat].

ABSTRACT

In the present study, the effects of microiontophoretically applied U-50488 on the spontaneous discharge of respitation related units (RRUs) in nucleus ambiguus or rats were observed. Of 96 RRUs recorded, U-50488 produced depressant effect on 51 units, excitative effect on 11 units, excitation followed by depression on 6 units, depression followed by excitation on 3 units. The remaining 25 units were not influenced. Naloxone administered iontophoretically not only blocked U-50488-induced depression in 12 out of 16 units, but also blocked U-50488-induced excitation in 2 units. Duration of the depression produced by U-50488 was remarkably longer than that of excitation. The result suggested that kappa receptor might be involved in respiratory regulation and that the subtype of opiate receptors which mediates depression and excitation effect might not be the same.