Abstract
The premotor neurons for cardiovascular sympathetic nerves are located in the rostral ventrolateral medulla (RVLM) and are called RVLM neurons. Activities of peripheral sympathetic nerves are not always changed in a uniform way and this phenomenon is known as a ‘regional difference’. For example, the cutaneous vasoconstrictor fibers participate in thermoregulation while vasoconstrictor fibers for the visceral and muscular vessels play an important role in regulation of arterial pressure. No neural mechanism of the regional difference has been established. We tried to identified reticulospinal neurons in the rostral medulla of the anesthetized rabbits; 1) premoter neurons for cutaneou vasoconstrictors and 2) ones for the cardiac sympathetic nerve. Warm stimulation of the preoptic area and anterior hypothalamus, the thermoregulatory center, inhibited activity of the cutaneous sympathetic nerve activity. We found reticulospinal neurons in the rostral ventromedial medulla that responded to the same stimulation with similar temporal response pattern of the nerve, suggesting that these neurons were premotor neurons for cutaneous vasoconstrictors. Hypoxia inhibited the activity of the cardiac sympathetic nerve and the same stimulation concurrently inhibited some of the RVLM neurons. We thought these neurons were premotor neurons for the cardiac sympathetic nerve. These data indicated that the premotor neurons for the sympathetic nervous system were grouped in according to their function and this grouping is the fundamental mechanism of the regional difference. [Jpn J Physiol 55 Suppl:S61 (2005)]
