中文摘要：

许多分子质量较大的药物如肽类、蛋白质、基因和抗生素等很难通过血脑屏障（blood brain barrier，BBB）。进入脑内发挥作用。常用于提高脑内药物浓度的方法有局部脑室植入、利用高渗溶液或血管活性物质增加BBB开放等，但这些方法具有一定损伤性，仅适用于短期治疗药物。鼻腔给药（intranasal administration，in）被认为是可绕过BBB有效增加脑内药物浓度的途径之一。

英文摘要：

The purpose of this paper is to encapsulate neurotoxin-Ⅰ （NT-Ⅰ）, a kind of analgesic peptide, into polylactic acid （PLA） nanoparticles （NPs） and to evaluate their transport into the brain after intranasal administration （in） by use of mierodialysis sampling technique developed in our laboratory recently. NT-Ⅰ-NPs （NT-Ⅰradiolabeled with sodium ^125I-Iodide） were prepared by a double emulsification solvent evaporation method, and were characterized in terms of surface morphology, particle size distribution, zeta potential and entrapment efficiency. Then, NT-Ⅰ-NPs were administered intranasally or intravenously to rats and the radioactivities in periaqueductal gray （PAG） were monitored up to 240 min utilizing the microdialysis sampling technique. Nanoparticles prepared were spherical with homogenous size distribution. Their mean particle size and zeta potential measured were （65.3±10.8） nm and （ 28.6 ± 2.3） mV, respectively. The entrapment efficiency of NT-Iencapsulated into nanoparticles was （35.5 ±2.8） %. The brain transport results showed that the time to peak level （Tmax） of NT-I-NPs （in） was （65 ± 10） min approximately, apparently shorter compared with NT-Ⅰ-NPs [/v, （95 ±10） min] or NT-Ⅰ E/v, （ 145 ± 10） min ]. The concentration to peak level （Cmax） and the area under the curves from zero to 4 h （AUC0-4h） of each group followed this order： NT-Ⅰ-NPs （in） 〉 NT-Ⅰ-NPs （iv） 〉 NT-Ⅰ （iv）. With nanoparticles as carriers and administered intranasally could be a potential way for centrally active peptides to improve their brain transport. Microdialysis is quite a good technique for the study of drug delivery to the brain.