Evidence for a bulbospinal serotonergic pressor pathway in the rat brain.
The cardiovascular role of spinal serotonin (5-HT) neurones descending from 5-HT cells near the ventrolateral surface of the medulla oblongata was investigated by stimulating these cells in normal animals and in animals with selective chemical ablation of 5-HT nerves. These laterally placed 5-HT nerves fall within the B1 and B3 groups in the medulla and were identified using immunohistochemistry. 5,7-Dihydroxytryptamine (5,7-DHT) was injected into the lateral cerebral ventricle (i.c.v.) to produce a generalized destruction of central 5-HT pathways, with preliminary intraperitoneal administration of desipramine to prevent depletion of noradrenaline stores. In other experiments, 5,7-DHT was injected directly into the cervical spinal cord, after preliminary treatment with desipramine, to produce selective destruction of spinal 5-HT nerves, confirmed both biochemically and immunohistochemically. Electrical stimulation near the lateral 5-HT cells in the B1 and B3 cell groups elicited pressor responses in control (vehicle-injected) rats; the increase in mean arterial pressure was proportional to the intensity and to the frequency of stimulation. Microinjections of kainic acid or L-glutamate at the same sites also produced an increase in mean arterial pressure. Selective destruction of 5-HT nerves, whether produced by i.c.v. or intra-spinal administration of 5,7-DHT, reduced the magnitude of the pressor response to electrical stimulation by over 50%. These experiments suggest the activity of 5-HT nerve cells adjacent to the ventrolateral surface of the medulla oblongata and projecting to the intermediolateral cell column serves to elevate arterial pressure and maintain vasomotor tone.
D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001921:Brain / Q000502:physiology*; D004553:Electric Conductivity; D004558:Electric Stimulation; D007031:Hypothalamus / Q000502:physiology; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D008636:Mesencephalon / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology*
D015116:5,7-Dihydroxytryptamine; D012701:Serotonin