Effects of behavior and social condition on cardiovascular response to footshock stress

Rats were instrumented with arterial catheters and directional-pulsed Doppler flow probes for assessment of blood pressure, heart rate, and blood flow in the renal, mesenteric, and hindquarter vascular beds. Subjects were tested in an intermittent shock procedure under paired and isolated social conditions and the cardiovascular indices associated with first shock, prone immobile behavior, upright behavior, and boxing behavior were recorded. Both shock procedures resulted in increased heart rate, mesenteric resistance, and renal resistance, as well as decreased hindquarter resistance. Blood pressure response was variable. Social and behavioral conditions generally accounted for little variance in cardiovascular indices during the treatments. Blood pressure assessed 2.5 min after the last shock was significantly higher in the isolated shock condition. In the context of divergent results from previous research in the area, the current results are most consistent with the view that a similar form of cardiovascular adjustment is present under paired and isolated shock, but that under some conditions the presence of a conspecific or the opportunity to fight may attenuate cardiovascular response to shock.