[Effect of destruction of nucleus reticularis gigantocellularis of rat medulla oblongata on morphine analgesia].
It was confirmed that the nucleus reticularis gigantocellularis (NRGC), including the nucleus reticularis paragigantocellularis (NRPG), was a highly sensitive site in the production of morphine analgesia by the micro-injection technique (ED50 = 8.5 ng/rat). The NRGC of SD male rats (280-350 g) was bilaterally lesioned by direct current (0.5 mA for 40 sec). The body weight was decreased by NRGC destruction, while no abnormality in motor activity was observed in NRGC-destructed rats. The size of lesion was decreased in relation to the days after operation. The size of the destructed area immediately after operation was about 30% of the NRGC area. Morphine analgesia was estimated by tail pinch and hind paw pressure tests. No change in control pain threshold was produced by NRGC lesioning. Morphine analgesia due to 5, 10 and 15 mg/kg s.c. were depressed almost equally be NRGC lesioning, and depression % was 60-70%. Time course of the morphine effect in NRGC-destructed rats was similar to that in sham operated rats. The degree of depression of morphine analgesia by NRGC lesioning was dependent on the extent of NRGC lesioning, i.e., the more the destructed area of NRGC was extended, the more the morphine analgesia was depressed. Reduction of morphine analgesia in rats in which the position of destruction had deviated from the NRGC was smaller than that in rats in which the destruction was exactly at the NRGC. These results suggest that the NRGC, including the NRPG, plays an important role in morphine analgesia.
D000698:Analgesia; D000818:Animals; D001835:Body Weight; D004305:Dose-Response Relationship, Drug; D004560:Electricity; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D009020:Morphine