Influences of Electrolytes on the Action of Morphine and Naloxone in Guinea-pig Ileum

해명(海冥) 회종편(回腫片)에서 Morphine과 Naloxone 작용(作用)에 미치는 전해질(電解質)의 영향(影響)

The influence of electrolyte concentrations on the action of morphine and naloxone was studied in the myenteric plexus-longitudinal muscle preparation of guinea-pig ileum to examine whether opiate receptor binding obseved in vitro with homogenates represents binding to the pharmacological receptor. The preparations were suspended in a modified Krebs-Henseleit bicarbonate buffer solution and electrically stimulated at 0.2 Hz. Morphine inhibited electrically evoked contractions; the concentration of morphine required for a 50-percent inhibition was 190 nM. This inhibitory action of morphine was potentiated in a medium containing lower concentrations of : $Na^+\;or\;K^+$, or by the addition of $Mn^{2+}$ to the medium, and weakened by increasing the concentration of $Ca^{2+}$ or decreasing the concentration of $Mg^{2+}$. Naloxone antagonized these actions of morphine: however, $pA_2values$ for naloxone (indices of affinity for antagonists, approximately 8.8) were unaffected by these electrolyte concentrations. Thus, changes in the inhibitory action of morphine caused by alterations in electrolyte concentrations are probably not the result of changes in the affinity of the receptor for opiates, but due to alterations in the events which precede or follow the receptor binding. Effects of electrolytes on the affinity of the functional opiate receptor for naloxone in guinea-pig ileum are apparently different from those reported with the specific binding sites for opiates in brain homogenate.

Guinea-Pig의 myenteric plexus-longitudinal muscle preparation에서 morphine과 naloxone 효과(效果)에 미치는 전해질(電解質)의 영향(影響)을 관찰(觀察)하였다. 표본(標本)은 Krebs-Henseleit bicarbonate tufter solution 으로 채운 organ bath에 현수(懸垂)하고 0.2Hz로 전기자극(電氣刺戟)하였다. Morphine은 전기자극(電氣刺戟)에 의(依)한 근편수축(筋片收縮)을 억제(抑制)하였으며, 이때 $ID_{30}$은 약(約) 190nM이었다. 이와같은 morphine의 억제작용(抑制作用)은 bath내(內) $Na^+$ 또는 $K+$ 농도(濃度)를 감소(減少)시키거나 $Mg^{2+}$을 가(加)하면 강화(强化)되었으며, $Ca^{2+}$ 농도(濃度)를 증가(增加)시키거나 $Mg^{2+}$를 농도(濃度)를 감소(減少)시키면 약화(弱化)되었다. Naloxone은 morphine의 작용(作用)을 억제(抑制)하였으며, 이때 naloxone에 대(對)한 affinity index인 $pA_2$ value는 약(約) 8.8이었고 that내(內) 전해질(電解質) 농도(濃度)를 변동(變動)시켜도 영향(影響)받지 않았다. 이 성적(成積)은 전해질(電解質) 변동(變動)으로 인(因)한 morphine의 작용변동(作用變動)은 전해질(電解質)이 opiate receptor의 affinity를 변동(變動)시킨다는 opiate-receptor binding실험(實驗)에서와는 달리 전해질(電解質) 변동(變動)에 의(依)한 functional opiate receptor의 affinity 변동(變動)에 의(依)한 것이 아님을 시사(示唆)한다.