Catecholamines in paraganglia associated with the hepatic branch of the vagus nerve: effects of 6-hydroxydopamine and reserpine.
Paraganglia are clusters of cells containing catecholamines (CA), mainly norepinephrine (NE) and dopamine (DA). The presence of epinephrine (E), on the other hand, has only been determined by indirect methods in retroperitoneal paraganglia of newborn and aged rats. Because their location, paraganglia associated with the hepatic branch of the vagus nerve may be a possible source of CA for the liver. The main purposes of the present study were to determine CA levels and whether E can be found in the omentum minus which includes paraganglia associated with the hepatic branch of the vagus nerve, and then to study the effects of 6-hydroxydopamine and reserpine on their CA content. Twenty-four female Wistar rats were randomly ascribed to three groups receiving two intraperitoneal injections of either 6-hydroxydopamine, reserpine or saline. Twenty-four hours after the last administration the rats were anesthetized and a portion of the omentum minus was obtained. Left adrenal medulla and a liver fragment were also collected as controls. The samples were processed to be analyzed by high performance liquid chromatography and catecholamine histofluorescence. The results confirm previous reports about the presence of considerable amounts of norepinephrine and dopamine in paraganglia. Norepinephrine and dopamine in the omentum like the adrenal medulla were significantly depleted by reserpine but not by 6-hydroxydopamine treatment, suggesting that some other sources in addition to sympathetic terminals are responsible for CA in the omentum. On the contrary, both drugs reduced liver NE, consistent with the localization of this amine mainly to hepatic sympathetic terminals. Histofluorescence of the omentum revealed 2-4 paraganglia per tissue fragment. Paraganglia associated with the hepatic branch of the vagus nerve contain also E. The presence of perihepatic sources of extra-adrenal CA, and more specifically E, could be of physiological significance.
Piñon
M
M
Departamento de Fisiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City, Mexico. mpinon@vmredipn.ipn.mx
Racotta
I S
IS
Ortiz-Butron
R
R
Racotta
R
R
D000313:Adrenal Medulla / Q000294:innervation / Q000502:physiology; D018759:Adrenergic Uptake Inhibitors / Q000494:pharmacology*; D000818:Animals; D002395:Catecholamines / Q000502:physiology*; D002851:Chromatography, High Pressure Liquid; D005260:Female; D007274:Injections, Intraperitoneal; D008099:Liver / Q000187:drug effects / Q000294:innervation*; D009852:Omentum / Q000294:innervation / Q000502:physiology; D016627:Oxidopamine; D010234:Paraganglia, Nonchromaffin / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012110:Reserpine / Q000494:pharmacology*; D013563:Sympathectomy, Chemical; D013565:Sympatholytics; D014630:Vagus Nerve / Q000187:drug effects / Q000502:physiology*
D018759:Adrenergic Uptake Inhibitors; D002395:Catecholamines; D013565:Sympatholytics; D012110:Reserpine; D016627:Oxidopamine