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This Article Full Text Full Text (PDF) Data Supplement All Versions of this Article: 571/2/441    most recent jphysiol.2005.100677v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Marina, N. Articles by Gilbey, M. P. Search for Related Content PubMed PubMed Citation Articles by Marina, N. Articles by Gilbey, M. P. Related Collections Integrative

¹ Department of Physiology, University College London, Hampstead Campus, London NW3 2PF, UK

When applied in vitro to various CNS structures 5-HT and/or NMDA have been observed to generate rhythmic nervous activity. In contrast, reports of similar in vivo actions are relatively rare. Here we describe a physiological sympathetic motor rhythm regulating the thermoregulatory circulation of the rat tail (T-rhythm; 0.40–1.20 Hz) that can be elicited following intrathecal (I.T.) application of 5-HT to an in situ‘isolated’ spinal cord preparation (anaesthetized rats spinalized at T10–T11 and cauda equina cut). I.T. injections were delivered to L1 as sympathetic neuronal activity to the tail (SNAT) arises from preganglionic neurones at T11–L2. SNAT was abolished after spinal transection (n= 18) and it did not return spontaneously. The administration of 5-HT (250 nmol) generated rhythmic sympathetic discharges (n= 6). The mean frequency of the T-like rhythm during the highest level of activity was 0.88 ± 0.04 Hz which was not significantly different from the T-rhythm frequency observed in intact animals (0.77 ± 0.02 Hz; P > 0.05 n= 16). In contrast, NMDA (1 µmol) generated an irregular tonic activity, but it failed to generate a T-like rhythm (n= 9), even though the mean levels of activity were not significantly different to those produced by 5-HT. However, 5-HT (250 nmol) applied after NMDA generated a T-like rhythm (0.95 ± 0.11 Hz, n= 6). Our observations support the idea that 5-HT released from rostral ventromedial medullary neurones, known to innervate sympathetic preganglionic neurones, can induce sympathetic rhythmic activity.

(Received 25 October 2005; accepted after revision 4 January 2006; first published online 5 January 2006)
Corresponding author M. P. Gilbey: Department of Physiology, University College London, Hampstead Campus, London NW3 2PF, UK. Email: m.gilbey{at}ucl.ac.uk

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