A refined method for sequential blood sampling by tail incision in rats

Levels of endogenous or administered substances can be estimated by blood s ampling. This allows an evaluation of the relationship between clinical sig ns, physiological parameters, pharmacological treatments and behaviour of t he animal. We show that blood samples can be taken occasionally as well as sequentially by means of a small incision at the end of the rats' tails. Up to 300 mu l of blood can be collected within 90 s. The advantages of this method are: (i) anaesthesia and surgery or restraint of the animal are net necessary; (ii) the procedure can be considered stress-free as indicated by the low, basal levels of the stress hormone corticosterone, even with freq uent sequential blood sampling over 3 h; and (iii) it can be used for longi tudinal studies allowing intra-individual comparisons over months and even years. Blood samples collected via an intravenous catheter and, at the same time, by our tail incision method resulted in comparable amounts of cortic osterone. Moreover, we consider the tail incision method for rats to be 'an imal-friendly' and a real alternative to ether conventionally used blood sa mpling techniques.