Behaviour of golden hamsters (Mesocricetus auratus) - Vetsuisse ...

negative feedback of cortisol: increasing cortisol levels suppress the release of ACTHin the pituitary gland.ACTH seemed to increase with increasing duration of sampling, although notsignificantly. It is the first hormone that is released in a stress situation and increaseswithin a few seconds until a negative feedback of the glucocorticoids starts. Becauseof the immediate reaction it is not possible to draw any conclusions about the stresslevel. In series 4 we measured 13 values below 2 pg/ml. The reason for such smallvalues could be the fast decomposition of ACTH due to the negative feedback, whichdoes not explain why it occurred so frequently in series 3.Our data show that sampling blood for measuring chronical stress must be takenquickly, at least within 2.5 minutes, before levels rise due to the acute stress ofsampling. This might be difficult because the (Swiss) Animal Welfare Legislationforbids decapitation without previous anaesthesia. For more accurate valueshamsters could be administered with a catheter, yet it is very difficult in this speciesand causes stress itself. There is no solution for cages with deep bedding, for thetime until hamsters are caught out of their cages can take just as long as the PAAsystem needs to react to acute stress.Faecal samples have their advantage in being non-invasive, a critical drawback isthat it gives only average hormone levels over a, sometimes unknown, period andthis method is sometimes not validated (Buchanan and Goldsmith, 2004). During theACTH-challenge test no increase in suspected metabolites of cortisol was found inthe faeces (unpublished data).Blood samples were taken on two following days. Although the duration ofanaesthesia and total duration of sampling did not differ significantly among days ofsampling, there was a tendency of higher values of total duration of sampling on day1. Corticosterone levels on day 2 were lower than on day 1. It is likely that hamsters46