[Effects of microiontophoretically applied OMF on spontaneous discharges of respiration related units (RRUs) in the region of nucleus ambigus of rat].

ABSTRACT

In the present study, it was observed that ohmefentanyl (OMF) affected microiontophoretically applied spontaneous discharges of respiration related units (RRUs) in the nucleus ambigus of rats. Of 96 RRUS recorded, 48 units were depressed following OMF application, 14 units increased in discharges, 14 units increased and then decreased, 9 units decreased and then increased. The remaining 11 units were not influenced. Naloxone administered iontophoretically not only blocked OMF-induced depression in 11 out of 15 units, but blocked OMF-induced facilitation in 5 out of 6 units. U-50488 administered microiontophoretically antagonized OMF-induced depression in 9 out of 13 units. Duration of the depression produced by OMF was much longer than that of the facilitation. The result suggests that the subtype of opiate receptors mediating the depression seen to be different from that responsible for the facilitation.