PhD-project: A pig model on health damaging stress
Background
Stress constitutes the body’s first order of defence toward potential detrimental environmental influences. Exposure to aversive stimuli initiates a cascade of adaptive events. The events include reactions of the central nervous system (CNS), the autonomic nervous system, the neuroendocrine systems, and behaviour. The CNS is responsible for the perception of the stimuli and activation of an integrated response, which typically includes an unspecific behavioural response, the fight or flight response, which serves to eliminate either the stressor or the exposure to the stressor. In order to prepare the mobilization of the body’s physiological, metabolic, and immunological defences, the hypothalamic-pituitary-adrenocortical axis (HPA-axis), the sympatho-adrenomedullary axis (SA-axis), and the parasympathetic nervous system will be activated. The relative activation of the different axes and systems depends on the inherent and acquired features of the individual, its previous experience with the actual stressor, and on the quantitative and qualitative properties of the stressor.
Individual differences in stress reactivity are amongst socially organised animals partly ascribed by the individual’s social position. The individual’s sense of control and predictive information about timing, severity or duration of the stressor are important features of responding. Both dominant and subordinate status specifies distinct behavioural repertoires, besides distinct physiological profiles, thus favouring different physiological processes in the body. Dominant animals in stable groups have been found to have higher levels of brain dopamine than subordinates. Opposite, subordinates are reported to have higher levels of serotonin and serotonin metabolites than dominant animals. Different activation of these components is important
Agonistic interactions, as inherent with dominance hierarchies, are considered social stress. Thus, a differentiation of group members according to the different ranks they possess, possibly constitutes a natural stress model. Social stress is associated with greater hormonal and cardiovascular changes than non-social stressors. The highest hormonal activity within stress hormones is observed in subdominants followed by subordinates and dominants. Pure physiological effects aside, social stress is reported to have a strong impact on immune functions in a large number of animal species, besides humans. In pigs, dominance status has been found to affect immune responses after social disturbances, and to affect disease susceptibility in undisturbed surroundings. Important mediators of stress effects on the immune system seem to be glucocorticoids and dopamine.
Aim
- To investigate how high, middle, and low ranking individuals differ in dopamine D2/D3 receptor density on lymphocytes and granulocytes, immune function and expression of behavioural and endocrine stress responses.
- To investigate how differences in controllable and/or predictable resource restriction affect dopamine D2/D3 receptor density on lymphocytes and granulocytes, and how unpredictable and uncontrollable stress-induced variation in dopamine D2/D3 receptor density affect immune function, susceptibility to disease, and expression of behavioural and endocrine stress responses in different ranking individuals.
Ansvarlig: Seniorforsker Karin Hjelholt Jensen
Projektperiode: 01.04.2004 - 31.12.2006
Samarbejdspartnere:
PhD-student: Bodil M. Hjarvard
Local supervisors: Karin Hjelholt Jensen, Helle Juul-Madsen
Supervisor: Ole Næsbye Larsen, University of Southern Denmark
Last updated: Thursday 21 June 2007 - [email protected]
Tel: +45 8999 1900