In vivo release of serotonin in cat dorsal vagal complex and cervical ventral horn induced by electrical stimulation of the medullary raphe nuclei.
Extracellular levels of serotonin (5-hydroxytryptamine; 5-HT) were monitored by microdialysis in the dorsal vagal complex (DVC) and the ventral horn of the spinal cord at the level of the phrenic motor nucleus in decerebrated cats. A selective serotonin uptake inhibitor, alaproclate (10(-4) M) was included in the dialysis probe perfusion fluid to increase basal and stimulated levels of 5-HT. Electrical stimulation (30 Hz, 10 V, 0.5 ms) in the nucleus raphe obscurus, containing neurons projecting to the DVC and to the ventral horn, induced a 2-3-fold increase of the 5-HT release in both these regions. After termination of the stimulation, the release gradually decreased during the following 60 min. Substance P, which coexists with 5-HT in descending neurons, did not significantly affect the 5-HT release when it was added (100 microM) to the probe perfusion fluid. The present findings are in accordance with the hypothesis that prolonged release of 5-HT is responsible for the previously demonstrated long-lasting facilitation of phrenic activity following raphe obscurus stimulation.
Brodin
E
E
Department of Pharmacology, Karolinska Institute, Stockholm, Sweden.
Linderoth
B
B
Goiny
M
M
Yamamoto
Y
Y
Gazelius
B
B
Millhorn
D E
DE
Hökfelt
T
T
Ungerstedt
U
U
D000818:Animals; D002415:Cats; D002851:Chromatography, High Pressure Liquid; D003655:Decerebrate State; D003956:Dialysis; D004558:Electric Stimulation; D005260:Female; D005455:Fluorescent Antibody Technique; D007150:Immunohistochemistry; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000502:physiology*; D010791:Phrenic Nerve / Q000502:physiology; D011903:Raphe Nuclei / Q000502:physiology*; D012701:Serotonin / Q000378:metabolism*; D013116:Spinal Cord / Q000378:metabolism* / Q000502:physiology; D013373:Substance P / Q000494:pharmacology; D014630:Vagus Nerve / Q000378:metabolism*
D012701:Serotonin; D013373:Substance P