Immunosympathectomy and avoidance behaviour in mice

Abstract

W. B. Cannon and his co-workers during the 1930's had purported to have demonstrated the non-essential character of the sympathetic nervous system's role in mediating emotion, but later workers using behavioural studies have tended to implicate the system in emotional behaviour. In this thesis an immunological technique was used to induce hypotrophic growth in the sympathetic nervous system of neonatal rodents. The injection technique used a split- litter design with the control neonates being injected with normal horse serum (NHS) .Following failure to obtain behavioural separation between the immunosympathectomized (IS) and the control (NHS) litter- mates using standard active and passive avoidance tasks it was argued that the time course of these procedures allowed ample opportunity for internal compensatory mechanisms to mask any essential differences. Accordingly an avoidance task (startle response) with a very short time course was used to test the animals. This task also failed to show unequivocal behavioural separation. Measuring the catecholamine metabolism of the adrenals some evidence was obtained which showed that IS mice metabolized larger amounts of the sympathetic nervous system's transmitter substance, noradrenaline, when subjected to a novel or an avoidance task. Evidence was examined on the essential interaction between the sympatho-adrenal medulla and the pituitary-adrenal cortex axis. It was concluded that certain controls are essential if an unambiguous demonstration is to be made of these two important central nervous system's efferent outflows in emotional states. IS mice were placed on free operant avoidance schedules in specially constructed apparatus. The final experiment reported concerns an attempt to further reduce the range of IS mice adaptive responses by the use of an inclined alleyway avoidance task interpolated between two equal periods of free operant avoidance responding. It was finally concluded that unequivocal behavioural separation, using avoidance tasks, has not been shown between IS and control litterraate mice either in this thesis or other published work. Hypotheses are discussed as to why this should be so.