Insular cortex lesions alter baroreceptor sensitivity in the urethane-anesthetized rat.

Cardiovascular representation has been demonstrated within the insular cortex and lateralization has been previously inferred. In this study, baroreceptor gain was investigated in response to the systemic injection of the pressor agent phenylephrine (PE) and the depressor agent sodium nitroprusside (SNP) in 57 urethane-anesthetized, male Sprague-Dawley rats before and after single lesion placement. Lesions mainly confined to the anterior insula (left or right) or the adjacent cortex were without significant effect on baroreceptor gain. Left posterior insular lesions, however, significantly increased baroreceptor gain (p<0.0001) whereas right posterior insular lesions had no effect on baroreceptor gain although heart rate and blood pressure were both significantly increased after lesion placement (p<0.05). These data suggest that: (1) the posterior insula (and not surrounding cortex or anterior insula) is primarily involved in cardiovascular control; (2) the left insular cortex may be chiefly concerned with parasympathetic cardiac regulation. Conversely, the right posterior insular cortex may regulate both cardiac and vasomotor sympathetic tone, as has been suggested in other species.