含量在毫微克分子以下的神经肽一般是用生物检定或放射免疫分析法测定的。这两种方法虽然灵敏度高

检出量小

但生物检定往往因动物品种不同或季节不同

实验的数This paper reports the method of ultramicroanalysis of small neuropeptide and the technic of perfusion which was used for collecting samples. Twenty mililitres of the perfusate was enough to estimate the quantity

to analyse the amino acids composition and to determine amino acids sequence of the peptide. We used this technic succesfully to isolate and identify a new opiate tetrapeptide (Asn-Ala-Gly-Ala) which was found in our laboratory. This peptide from the perfusate of rabbit PAG was first purified through a small column of Amberlite XAD-2 and then chromatographed on a polyamide layer sheet. The quantity of this peptide in the perfusate of rabbit PAG was determined by the scanning method of developed fluorescent spot on polyamide layer sheet. The level of the tetrapeptide in the perfusate of the rabbit PAG was increased about 4.80±0.98 nmole/ml perfusate(n=10

p<0.001) after electroacupuncture

and decreased about 2.95±0.51 nmole/ ml perfusate(n=8

p<0.002)after stimulating the brain.These results show that the peptide is related to the mechanism of both prosseses of analgesia induced by electroacupuncture and brain stimulation