The involvement of endogenous opioids in exploratory and emotional behaviour, induced by stress. Some age related differences

The Stress System is very important in the coordination of the generalised stress response, which takes place when a stressor of any kind exceeds a threshold. We refer to the state of stress as the 'General adaptation or Stress syndrome'. In our experiments we analysed some aspects of interaction between stress system and the endogenous opioid systems (e.o.s.). We also tried to present some aspects of the opioid involvement in the interactions between motivation, cognitive behaviour and emotions, as well as to present the relationships between physiological and behavioural mechanisms, either in normal conditions or under stress. Taking into account that the emotional states interfere with perception and cognition, in our experiments we used suitable variants of the Open-Field test, which evaluates the exploratory drive and emotional reactivity. In order to assess the behaviour of the animals (Wistar rats), we analysed exploratory (cognitive) and non-exploratory (emotional) parameters. To evaluate the manner in which endogenous opioid systems are involved in these aspects, we treated different groups of rats with opiate agonists and antagonists, before testing in Open- Field.