The Journal of physiology
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The Journal of physiology · Aug 1983
Sites and mechanism of action for the effects of intrathecal noradrenaline on thermoregulation in the rat.
1. In unanaesthetized rats, intrathecal injection of 0.30 mumole noradrenaline (NA) at the level of the lumbar enlargement produced a transient rise in core temperature followed by prolonged hypothermia and tail skin vasodilation.2. Studies of the distribution of [(3)H]NA injected at the lumbar enlargement revealed that at least 97% of the activity recovered from the central nervous system was located in the spinal cord, primarily within the thoracic and upper lumbar segments. ⋯ These injections produced an immediate increase in blood pressure. However, this effect was transient and, during most of the time when NA-induced vasodilation and hypothermia were present, blood pressure was normal or only slightly elevated. Thus, it is not likely that a baroreceptor-mediated reflex inhibition of sympathetic outflow contributed significantly to the vasodilatory or hypothermic action of NA.