The effect of baroreceptor stimulation on pain perception depends on the elicitation of the reflex cardiovascular response: Evidence of the interplay between the two branches of the baroreceptor system

• Study of the effect of carotid baroreceptor stimulation on pain and cardiovascular activity.
• Baro-stimulation decreased heart rate (HR) and blood pressure (BP).
• Pain reduction during baro-stimulation only occurs if the reflex HR response is elicited.
• Results support a connection between the central and cardiac branches of baroreceptors.

We examined the impact of baroreceptor stimulation on pain and cardiovascular responses in 39 healthy participants. Carotid baroreceptors were stimulated with external suction (−50 mmHg, stimulation) or pressure (+8 mmHg, control). Pain was induced by pressure to the nail of the left-index finger and quantified by a visual analog scale. Pain decreased heart rate (HR) and increased blood pressure (BP). Baroreceptor stimulation further decreased HR and reduced the BP increase. Pain experience failed to differ between baroreceptor stimulation conditions. However, significant results were obtained when trials were categorized according to the magnitude of the HR deceleration elicited by baroreceptor stimulation. In trials with strong baroreceptor-elicited HR deceleration pain intensity was lower than in trials both with inactive baroreceptor stimulation (pressure trials) or trials with small baroreceptor-elicited HR responses. Anti-nociceptive effects of baroreceptor stimulation depend on the activation of the reflex cardiovascular response. Central nervous inhibition due to baroreceptor stimulation only occurs if the peripheral cardiovascular response is engaged.