Significance of the cerebrovascular effects of immobilization stress in the rabbit.

Abstract

The question of the significance of the cerebrovascular effects of stressful situations in animals is still controversial. In the present article, an experimental model of immobilization stress in the rabbit is described, and its specificity in relation to arterial blood pressure and PaCO2 is investigated. CBF was measured with the multiregional tissue sampling technique using [14C]-ethanol as tracer. After dissipation of althesin anesthesia, the stress reaction was elicited by tactile abdominal stimuli. The response was evidenced by an instantaneous acute hypertension (+33.8% during the CBF measurement period). Within the first minute of the reaction, the CBF was significantly increased in all nine structures studied by 39% (caudate nucleus) to 82% (parieto-temporal cortex). The study of the influence of arterial blood pressure and the PaCO2 on CBF showed that cerebrovascular autoregulation and CO2 sensitivity were differently affected in the various structures during the stress reaction. However, the stress response of the brain circulation could not be entirely ascribed to one or both of these two systemic factors, thus suggesting the contribution of a local intrinsic activation. The model presented here could be useful for long-term studies of cerebrovascular repercussions of repeated acute hypertensions of a stressful nature.