Modulation of the migrating myoelectric complex by brain noradrenergic systems in rats

The respective role of central and peripheral noradrenergic systems in the control of migrating myoelectric complex (MMC) was investigated in rats following lesions with 6-hydroxydopamine (6-OHDA). 6-OHDA was injected via intraperitoneal (ip), intracisternal (icis), and intracerebroventricular (icv) routes in rats. Control animals received the vehicle alone. One month later, MMC was recorded in conscious rats chronically fitted with electrodes. The MMC period was significantly lengthened after 6-OHDA ip or icv injection, and slightly shortened after 6-OHDA icis injection. No disruption of central noradrenergic systems was detected after ip lesions. Norepinephrine content was reduced in the digestive tract after ip lesions, in the spinal cord after icis lesions, and in the cortex, the hypothalamus, pons-medulla, and the spinal cord after icv lesions. After icis lesions, noradrenergic perikarya were spared in pons-medulla, whereas only pons noradrenergic perikarya were lesioned after icv lesions. We conclude that lesions of brain noradrenergic systems modify MMC periodicity in rats. The rostral noradrenergic systems may play the major modulatory role.