Sympathetic nervous system and control of blood pressure during natural behaviour.

The role of the sympathetic nervous system in generating behaviourally linked blood pressure (BP) responses was investigated in awake rats instrumented for chronic intra-arterial BP recording. All data from the recording sessions were digitalized and processed by a computer. Frequency interval histograms of behaviourally associated changes of BP and heart rate (HR) were generated. 6-Hydroxydopamine (100 and 200 mg/kg intravenously) was used for chemosympathectomy. In the intact rats (n = 8) three different frequency histograms of mean BP values for three behavioural groupings were generated (from lowest to highest average values): (1) resting, (2) exploring-grooming and (3) eating-drinking. Chemosympathectomy (n = 5) abolished this order of BP changes; mean BP did not rise from rest to other behaviours, nor did it vary during different behaviours. It is concluded that the sympathetic nervous system is responsible for producing the changes in BP that are appropriate and characteristic of each behaviour in awake, unrestrained rats.