Exaggerated cardiovascular and behavioral nociceptive responses to subcutaneous formalin in the spontaneously hypertensive rat.

Spontaneously hypertensive rats (SHRs) are typically less responsive to phasic noxious stimuli than are their normotensive controls. Here, we used the formalin test to compare behavioral and cardiovascular responses to persistent noxious stimuli. Hindpaw formalin injection produced exaggerated flinching, arterial pressure and heart rate responses in SHRs, suggesting that abnormalities in blood pressure control systems increase nociceptive responses to persistent noxious stimuli.