SOMATOCARDIOVASCULAR REFLEXES IN ANESTHETIZED RATS WITH THE CENTRAL-NERVOUS-SYSTEM INTACT OR ACUTELY SPINALIZED AT THE CERVICAL LEVEL

The effects of noxious mechanical stimulation of various segmental areas on heart rate and mean arterial blood pressure (MAP), as well as cardiac and renal sympathetic nerve activities were examined in anesthetized rats with the central nervous system (CNS) intact or acutely spinalized at the cervical level. In CNS-intact rats, pinching for 20 s applied to any segmental skin area, but particularly that of the paw, produced an increase in heart rate, blood pressure and the sympathetic nerve activities. In acutely spinalized rats, pinching the chest, abdomen and back of the body produced large increases, while hindlimb and perineum stimulation induced only a small increase or no increase in heart rate, blood pressure and the sympathetic nerve activities. Stimulation of the right side produced particularly large responses in heart rate and stimulation of the ipsilateral side produced large responses in cardiac and renal sympathetic nerve activities in spinalized rats. These results suggest the existence of the two types of reflex responses, supraspinal and propriospinal, in the somatocardiovascular reflex. The supraspinal one has characteristics of diffuse reflex organization, while the propriospinal one has strong segmental and lateral organization.