Tree shrews (Tupaia belangeri chinensis) belong to the Tupaiinae family, Scandentia order. Since tree shrew has small body size, easy to propagate and has a close relationship with primates, it is more advantageous than rodents in modeling human diseases. These features of tree shrew also make it a candidate model animal of potential human diseases and could partly substitute the high-price non-human primates such as rhesus monkey.

Drug addiction is a chronic brain diseases and can cause lots of social problems. One of the common methods to study addiction is to establish addictive models. Master student, SUN Yongmei, from the Laboratory of Cognitive Disorder Research, Kunming Institute of Zoology, Chinese Academy of Sciences, carried out morphine addiction experiments in tree shrews under the instruction of Prof. MA Yuanye and associate Prof. WANG Jianhong.

Morphine, an agonist of opiate receptor, is clinically used as the pain killer. However, its usage is limited because of the tolerance, dependence and addiction. Naloxone can induce withdrawal syndromes on morphine dependent rats and mice and therefore establish the conditioned place aversion (CPA). In this study, SUN and her colleagues found that tree shrews could be morphine dependent after three injections with increasing doses of morphine per day. In addition, morphine dependent tree shrews showed withdrawal syndromes and could establish CPA after naloxone injection. This tree shrew model could be applied to investigate the neurobiological mechanisms of morphine addiction and screen drugs to relieve morphine withdrawal syndromes.

The results have been published on the special issue of Zoological Research (2012，Feb. 33(1): 14−18，DOI：10.3724/SP.J.1141.2012.01014).