[Effects of noxious and innocuous cutaneous stimulation on adrenal sympathetic efferent nerve activity in rats]

Present study was undertaken to elucidate the reflex effects of cutaneous mechanical stimulation on both adrenal sympathetic efferent nerve activity and secretion rates of the adrenal catecholamines (epinephrine and norepinephrine) in anesthetized rats. An attempt was also made to clarify the effect of clonidine on this cutaneo-adrenal medullary reflexes. The results obtained were as follows: In central nervous system (CNS) intact rats, noxious pinching stimulation of the lower chest or hindpaw skin produced reflex increases in both nerve activity and secretion rates of catecholamines from the adrenal medulla; innocuous brushing stimulation of the lower chest or thigh skin produced reflex decreases in nerve activity and secretion rates of catecholamines during stimulation period. In spinalized rats, noxious pinching stimulation of the lower chest skin produced reflex increases in both nerve activity and secretion rates of catecholamines, whereas pinching of hindpaw skin did not produce any reflex increases; innocuous brushing stimulation of the lower chest or thigh skin elicited reflex increases in both nerve activity and secretion rates of catecholamines although lower chest brushing elicited a much stronger response than thigh brushing did. These findings suggest that; the secretion of adrenal medullary hormones can be controlled reflexly by mechanical cutaneous stimulation through CNS via adrenal sympathetic efferent nerves; the excitatory effect of the cutaneo-adrenal medullary reflexes was independent of noxious or innocuous stimulation at the spinal level, whereas in CNS intact rats the effect was either excitatory or inhibitory in response to noxious or innocuous stimulation, respectively; there is a marked segmental organization of this reflex at the spinal level which is modified into a generalized response through supraspinal structures. Furthermore, it was also demonstrated in present experiment that clonidine produced a dose-dependent in these reflex responses in both CNS intact and spinalized rats.