IntroductionAn effective training of search-and-rescue dogs is the basis for a successful search for missing people, e.g. in avalanches. To evaluate different training methods and influential factors like outdoor conditions, markers are needed to assess fitness and constitution of dogs. One of those markers could be histamine. Histamine is released from mast cells not only by immunological but also by physical stimuli like cold, heat, or pressure [1]. Low temperature evoked histamine release can be due to both direct activation of skin mast cells [2] and neural modulation of intestinal mast cells [3]. A stress response may indicate an overloaded and, thereby, ineffective training of the dogs. An established stress marker in dogs is cortisol. Plasma cortisol concentration in dogs increases during cold stress [4] as well as during heat stress [5] and after exercise [6]. In this study, we investigated concentrations of plasma histamine and cortisol in search-and-rescue dogs under different training conditions.
Materials and methods16 rescue dogs (age: 1-11 years), trained in avalanche search, underwent four different types of strain. Two training types, running and searching, were carried out in summer and winter. The summer part was executed at an altitude of 700 metres and the winter part at an altitude of 2,600 metres. Strains had duration of 2 ¥ 20 min each and a 20 min Inflamm. res. 54, Supplement 1 (2005) S34-S35 break in between. Blood samples were taken before the strain (T0), after the two strain cycles (T60), and after a resting period of two hours (T180). Corresponding body temperature and outdoor temperature were measured. Plasma was analysed for histamine by ELISA and for cortisol by LIA (both assays: IBL, Hamburg, Germany). Data was analysed for differences between the four strain types (ANOVA), influences by season and training type (Two Way ANOVA), time-dependent changes (paired t-test), and a relationship between histamine, cortisol, outdoor and body temperature (linear regression model). Experimental procedures were approved by the Government of Upperbavaria (AZ 209.1/211-2531.2-7/02).
Results and discussionAlthough training types were executed under different conditions (altitude, outdoor temperature: range in summer: 9/26 degrees Celsius; range in winter: -18/-3 degrees Celsius), no significant changes in histamine concentration were found during the course of the four strain types (Table 1). Cortisol concentration did not increase during the different strains. However, it decreased significantly after the search strain (T60) in winter and returned (P < 0.05) thereafter (T180) to basal level (Table 1). At the three different sample times (T0, T60 or T180), no differences in histamine and cortisol concentrations were observed between the four strain types (Table 1). Analysing the influence of season (summer/winter) and training type (running/searching), a higher histamine concentration was obtained before any strain (T0) in summer vs. win- Table 1. Plasma histamine and cortisol concentrations in ...
