Renal sympathetic nerve activity and plasma catecholamines during eating in cats

We measured renal sympathetic nerve activity (RNA) and arterial plasma concentration of norepinephrine (NE) and epinephrine (EPI) before, during, and after eating in six conscious cats. Eating continued for a period of 5 min. RNA, heart rate (HR), and arterial blood pressure (AP) increased almost simultaneously with the onset of eating and reached a maximum value of 192%, 221 beats/min, and 121 mmHg at 2.5-5 min after the onset of eating, respectively. The plasma NE level increased significantly (P less than 0.05) during eating from the control value of 0.56 ng/ml and reached a maximum value of 1.33 ng/ml at 4.5-5 min, whereas the plasma EPI level did not change significantly from the control value of 0.12 ng/ml. The plasma levels of NE and EPI were unaffected by the blood samplings. The relationship between the changes in RNA and the plasma NE level during eating had a significant (P less than 0.05) positive correlation (r = 0.52). The result suggests that plasma NE concentration tends to increase with the rise in RNA during eating.