title: Axoplasmic transport of norepinephrine in the locus coeruleus-hypothalamic system in the rat.
abstract: The axoplasmic transport of norepinephrine (NE) between the nucleus locus coeruleus (LC) and the hypothalamus has been measured by three methods which employ the stereotaxic injection of [3H]catecholamines in the rat brain. [3H]NE is synthesized from [3H]dopamine (DA) injected into the LC and transported at a rate of 0.8-0.9 mm/h. This rate is probably an underestimate since it includes the time required for uptake and conversion of [3H]DA to [3H]NE prior to transport. Measurement of transport of [3H]NE between the posterior and anterior hypothalamus gives a rate of 2 mm/h which is independent of [3H]DA uptake and [3H]NE synthesis. This rate is in good agreement with the 1.9 mm/h figure calculated for [3H]NE transport in the system after LC injection of [3H]NE and represents a closer estimate of the true rate of axoplasmic transport than the 0.8-0.9 mm/h estimate. Transport of [3H]NE occurs through primarily ipsilateral NE fibers running in the median forebrain bundle and is blocked by 6-hydroxydopamine lesions in the bundle. Early appearing [3H]NE in the hypothalamus forms a relatively stable pool which is unaffected by median forebrain bundle lesions and is essentially unchanged by [3H]NE transported from the LC. This pool appears to be derived from non-specific spread of [3H]DA after injection, probably through the cerebrospinal fluid.
mesh_terms: D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001370:Axonal Transport; D002552:Cerebral Ventricles / Q000502:physiology*; D004298:Dopamine / Q000378:metabolism; D006892:Hydroxydopamines / Q000494:pharmacology; D007031:Hypothalamus / Q000502:physiology*; D007034:Hypothalamus, Posterior / Q000187:drug effects / Q000502:physiology; D008297:Male; D009434:Neural Pathways; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats
chemical_list: D006892:Hydroxydopamines; D004298:Dopamine; D009638:Norepinephrine