What is Chronic immobilization stress (CIS)?
There are >1200 articles tagged "chronic immobilization stress" on pubmed. 

From Hennebelle et al. (2012):


  Half of the 6-month old male rats from each dietary group were subjected to a validated chronic stress procedure (Buyntsky and Mostosky, 2009) based on a restraint stress procedure adapted from Veena et al, [32]. Rats were placed in wire mesh restrainers for 6 h a day (fom 10 am to 16 pm) for 21 days (5 days a week) over a period of 4 weeks. Unstressed rats were handled weekly. The unstressed and stressed animals were housed in different rooms.


Hennebelle, H., et al. 2012. Influence of Omega-3 Fatty Acid Status on the Way Rats Adapt to Chronic Restraint Stress. PLoSOne 7: e42142.