Freedman S B, Harley E A, Patel S
Merck Sharp and Dohme Research Laboratories, Neuroscience Research Centre, Harlow, Essex, U.K.
Eur J Pharmacol. 1989 Dec 19;174(2-3):253-60. doi: 10.1016/0014-2999(89)90317-8.
Muscarinic agents produce a range of side effects including hypothermia and tremor. Although these responses can be used to estimate the in vivo activity of these muscarinic agents in the central nervous system (CNS), the approach is limited by compensatory feedback mechanisms and the difficulty of equating degree of receptor occupancy to effect. We have developed an ex vivo assay to measure the potency and penetration of muscarinic agents into the CNS. The muscarinic antagonists scopolamine and N-methylscopolamine dose dependently inhibited the ex vivo binding of [3H]oxotremorine-M to homogenates of mouse whole brain membranes. Following intraperitoneal administration these compounds had ED50 values of 2.6 and 26 mg/kg respectively, which were comparable to the doses which inhibited RS86 induced hypothermia in mice. Three muscarinic agonists RS86, pilocarpine and arecoline also demonstrated CNS activity in this assay with ED50 values of 11, 23 and 220 mg/kg. RS86 and pilocarpine additionally showed good penetration into the CNS with estimated values of 1.5 and 0.31% of the administered dose. These values were comparable with the ability of these compounds to induce a centrally mediated hypothermic response. These studies demonstrate a simple, quick and reliable biochemical means of assessing a muscarinic agent's potency and penetration within the CNS.
毒蕈碱类药物会产生一系列副作用，包括体温过低和震颤。尽管这些反应可用于评估这些毒蕈碱类药物在中枢神经系统（CNS）中的体内活性，但该方法受到代偿性反馈机制的限制，且难以将受体占有率与效应程度等同起来。我们开发了一种体外测定法，以测量毒蕈碱类药物进入中枢神经系统的效力和穿透能力。毒蕈碱拮抗剂东莨菪碱和N-甲基东莨菪碱剂量依赖性地抑制了[3H]氧代震颤素-M与小鼠全脑膜匀浆的体外结合。腹腔注射后，这些化合物的半数有效剂量（ED50）分别为2.6和26 mg/kg，这与抑制小鼠RS86诱导的体温过低的剂量相当。三种毒蕈碱激动剂RS86、毛果芸香碱和槟榔碱在该测定中也显示出中枢神经系统活性，ED50值分别为11、23和220 mg/kg。RS86和毛果芸香碱还显示出对中枢神经系统的良好穿透性，估计值分别为给药剂量的1.5%和0.31%。这些值与这些化合物诱导中枢介导的体温过低反应的能力相当。这些研究证明了一种简单、快速且可靠的生化方法，可用于评估毒蕈碱类药物在中枢神经系统中的效力和穿透能力。
