κ-Opioid receptor mediates the antinociceptive effect of nitrous oxide in mice

BACKGROUND

Our previous reports demonstrated that genetic deletion of μ-opioid receptor has no influence on the anaesthetic and antinociceptive effects of nitrous oxide (N2O) in mice, and that an antagonist selective for κ-opioid receptor (KOP), but not that selective for δ-opioid receptor, suppresses the antinociceptive effect of N2O. However, it is not known whether genetic deletion of KOP affects the N2O actions.

METHODS

We measured the minimum alveolar concentration (MAC) of volatile anaesthetics in the absence and presence of N2O. The antinociceptive action of N2O was tested by an acetic acid-writhing test and a hot-plate test. The number of c-Fos-immunopositive cells in sections from the lumbar spinal cord was counted to test whether the descending inhibitory system participates in the pharmacological action of N2O. The hypnotic action of N2O was assessed by measuring the N2O-induced decrease in the EC50 for loss of the righting reflex (EC50-LORR) of sevoflurane.

RESULTS

Sevoflurane MAC was not significantly reduced by N2O and its antinociceptive action was almost completely abolished in KOP-knockout (KO) mice. The N2O-induced increase in c-Fos-immunopositive cells in laminae III-IV of the lumbar spinal cord was significant in wild-type (WT), but not in KOP-KO mice. In contrast, sevoflurane EC50-LORR was similarly reduced by N2O in WT and KOP-KO mice.

CONCLUSIONS

Our study suggests that N2O demonstrates its antinociceptive action and reduces sevoflurane MAC in mice through KOP activation, whereas its hypnotic potency is not dependent on KOP activation.

[A comparative study on the serum and tissue 5-FU concentrations in patients with hepatocellular carcinoma after preoperative oral administration of UFT and 5'-DFUR]

UFT or 5'-DFUR was orally administered to the patients with hepatocellular carcinoma preoperatively and the concentrations of these drugs and 5-FU in the serum, liver tissue and cancer tissue obtained at the time of operation were measured. The unchanged 5'-DFUR was not detected in any of these samples. The concentration of 5-FU in cancer tissue was significantly higher in UFT treated group (0.409 microgram/g) than that in 5'-DFUR group (0.040 microgram/g). However, the 5-FU levels in the serum and noncancerous liver tissue were also higher than those in the patients with other organ cancers. Although UFT is a useful drug for the adjuvant chemotherapy of hepatocellular carcinoma, the dose was considered to be minimized to avoid the side effects since the activity of drug-metabolizing enzymes may be decreased in hepatocellular carcinoma complicated with liver cirrhosis.

[Studies on the efficacy and safety of panipenem/betamipron in infections in surgical domain and the safety when mixed with lactate containing infusion]

Studies were done on the effectiveness and safety of panipenem/betamipron, a new carbapenem antibiotic, in infections in the surgical domain and its safety when dissolved in infusions containing lactate. The obtained results are summarized as follows. The preparation, 0.5 g/0.5 g or 1.0 g/1.0 g, was administered by intravenous drip infusion 2 to 3 times a day to 31 cases of patients with infections in the surgical domain. A physiological saline solution was used as the solvent in 21 cases (group A) of them and Solita T3, an infusion containing lactate, was used as the solvent in the 10 remaining cases (group B). As for its clinical effects, results were rated as "excellent" in 20, "good" in 7, "fair" in 3 and "no response" in 1 out of the 31 cases, and the efficacy rate was 87.1%. Regarding its bacteriological effects, results were rated as "disappeared" in 22, "decreased" in 2, "unchanged" in 1 and "unknown" in 1 out of 26 cases from which bacteria were isolated, hence the bacteria-clearance rate was 88.0%. As for side effects, skin rash was seen in 1 case and slight increases of GOT and GPT were noted as abnormal changes in laboratory data in 2 cases. These side effects were all observed among the cases in group A but not at all in group B where a lactate containing infusion was used as the solvent.

[A case of gastric metastases from carcinoma of the breast]

Reported is a case of a gastric metastases from a cancer of the breast in a 54-year-old woman who had received a standard radical mastectomy for a cancer of the right breast (T2N1bM0). Microscopic examination had revealed a lobular carcinoma, partially showing a signet ring appearance, and metastases in 4 axillary lymph nodes. Two years and 6 months later as a result of an upper GI series and a gastroscopy, linitis plastica was observed. Because there were no other metastatic lesions, a laparotomy was performed. The stomach, however, was unresectable. Further, a nodal biopsy revealed a metastatic breast cancer. Because of the probe laparotomy, however, the patient's symptoms were aggravated for several months. Death occurred three years and five months after the mastectomy. An autopsy revealed systemic metastases which included the stomach that had originated from her breast.

[Effects of cisapride on lower esophageal sphincter pressure and gastroduodenal motor activity in man]

Manometric study was performed to investigate the effects of cisapride, a new non-antidopaminergic gastrointestinal prokinetic compound, on interdigestive lower esophageal sphincter pressure (LESP) and gastroduodenal motility using infused catheter technique. The subjects consisted of 9 healthy volunteers and 29 patients with progressive systemic sclerosis (19), reflux esophagitis (8) and others (2). 4 mg of cisapride was given by bolus injection, continuous infusion or oral administration. The following results were obtained: Intravenous and oral cisapride increased LESP compared with basal pressure. Especially, bolus injection of cisapride caused a significant elevation of LESP during 30 minutes after administration. After administration of cisapride, gastroduodenal motility was accelerated gradually, then inducing IMC-like contractions. By bolus injection, IMC-like contractions were induced in healthy subjects more frequently than in patients group. On the other hand, motility index of stomach and duodenum showed persistent increase in patients group compared with healthy subjects. Cisapride-induced IMC-like contractions initiated from LES and upper part of stomach and mediated to duodenum, though aborad migration was not confirmed in the present study.

[Comparative study on the inhibitory effect of glucagon and secretin on the gastroduodenal motility in man]

Manometric study was performed to compare the inhibitory effect of glucagon and secretin on the gastroduodenal motor activity by infused catheter method. The subjects consisted of 3 healthy volunteers and 7 patients with peptic ulcer and other diseases. The following results were obtained. After the intravenous administration of glucagon (1 mg), the motor activity of the stomach and duodenum was inhibited promptly. According to statistic evaluation, the contraction numbers and motility index decreased significantly during 25 minutes compared with the basal values in both stomach and duodenum. After the administration of secretin (100 units), gastric motor activity was markedly inhibited, although duodenal motility increased during 10 minutes due to the initiation of secretin-induced migrating motor complex. The contraction numbers and motility index in stomach decreased significantly during 20 minutes after the administration. The inhibitory effect of glucagon was more remarkable in duodenum than in stomach. On the other hand, secretin was more effective in stomach than in duodenum.