Biphasic effects of the anterior cingulate cortex stimulation on glabrous skin blood flow in rats

A growing body of evidence indicates that the anterior cingulate cortex (ACC) is associated with sensory, cognition and emotion processing. We have shown that electrical stimulation of rat ACC depressed the spinal cord dorsal horn neuron activity in response to noxious stimuli, possibly through a release of GABA. GABA may elicit dorsal root reflexes (DRRs) to induce peripheral vasodilatation. On the other hand, the ACC may also regulate autonomic flow via the lateral hypothalamus (LH). The goal of this work was to investigate the role of ACC in regulating autonomic activity. A laser Doppler imager was used to continuously monitor rat glabrous skin blood perfusion in both hind paws, while a simultaneous heart rate (HR) and DRRs were recorded to assess contributions of sympathetic flow and sensory afferent to the ACC-induced vascular change. Twenty-three rats were divided into three groups: a unilateral electrolytic LH lesion group (n = 6), a sham lesion group (n = 9), and a control group (neither lesion nor stimulation, n = 8). ACC stimulation induced a biphasic systemic vascular response, with an initial transient cutaneous vasoconstriction followed by a prolonged vasodilatation. Unilateral LH lesion did not alter this biphasic response. A short-term tachycardia occurred in response to the ACC stimulation, but did not correlate with the prolonged vasodilatation. No significant change in DRRs was found (in 35 fibers). ACC stimulation induced a biphasic vascular response in the skin. Data are consistent with sympathetic contribution. However, other mechanisms should also be involved.