D-フェニルアラニンの鎮痛増強作用に関する研究
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Our previous studies revealed that : 1) an endogenous morphine-like factor (MLF) is involved in acupuncture analgesia (AA) since naloxone antagonizes AA measured in rats by the tail-flick test ; 2) the individual variation in effectiveness of AA is parallel to the contents of MLF in the rat brain and 3) D-phenylalanine (DPA) enhanced AA in acupuncture non-effective animals, and hence, the individual variation of effectiveness in AA was abolished by pretreatment with 250 mg/kg DPA administered intraperitoneally. In the present experiment, the intrinsic mechanism of DPA action on enhancement of AA in acupuncture non-effective animals was investigated by observing the effect of DPA on analgesia caused by intraventricularly injected methionine-enkephalin (Met-E) or β-endorphin (β-E) under the supposition that Met-E or β-E is a MLF in causing AA. Intraventricular (D-ala<SUP>2</SUP>) Met-E (10 μg), which is hardly degraded by aminopeptidase, was markedly enhanced by pretreatment of intraperitoneal DPA 250 mg/kg or intraventricular DPA 80 μg. Analgesia caused by intraventricular β-E (3μg) or morphine (1.5 μg) was also enhanced by intraventricular DPA. 100 mg/kg or 300μg 3-phenylpropionic acid intraperitoneally or intraventricularly, caused stronger inhibition of carboxypeptidase A than that by DPA, but did not enhance analgesia caused by intraventricular (D-ala<SUP>2</SUP>) Met-E. Intraperitoneal bacitracin (50 mg/kg), an inhibitor of carboxydipeptidase, had no effect on intraperitoneal morphine (0.5 mg/kg) analgesia of acupuncture effective animals, nor on acupuncture non-effective animals. Inhibitory action of various inhibitors on carboxydipeptidase and aminopeptidase was measured by high performance liquid chromatography (HPLC), measuring the product of Met-E, tyrosyl-glycyl-glycine and tyrosine, respectively. As a result, the inhibitory action on carboxydipeptidase was : o-phenanthroline> TG> bacitracin> 3PPA> DPA, while that on aminopeptidase was : bacitracin> puromycin> o-phenanthroline > 3PPA> DPA. DPA was the weakest inhibitor on carboxydipeptidase, as well as on aminopeptidase. From these results, it was concluded that the enhancement of AA by DPA is not attributed to the inhibitory action of DPA on the degrading enzymes of Met-E or β-E, but to another DPA action.
- 学校法人 昭和大学・昭和医学会の論文
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