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This Article Full Text Full Text (PDF) All Versions of this Article: 566/3/807    most recent jphysiol.2005.089581v1 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 Hunt, P. N Articles by Bosma, M. M Search for Related Content PubMed PubMed Citation Articles by Hunt, P. N Articles by Bosma, M. M

¹ Department of Biology, University of Washington, Seattle WA 98195-1800, USA

Spontaneous, synchronous activity occurs in motor neurones of the embryonic mouse hindbrain at the stage when rhombomeric segmentation disappears (embryonic day 11.5). The mechanisms generating and synchronizing the activity, however, and the extent to which it is widespread in the hindbrain, are unknown. We show here that spontaneous activity is initiated in the midline of the hindbrain, and propagates laterally to encompass virtually the entire hindbrain synchronously and bilaterally. Separation of the midline region from lateral regions abolishes or slows activity laterally, but not medially. The early differentiating neurones of the midline raphe system are present in the rostral midline and express serotonin at E11.5. Their axons ramify extensively in the marginal zone, cross the midline, and extend at the midline both rostrally into the midbrain and caudally towards the caudal hindbrain. Blockers of serotonin receptors, specifically the 5-HT_2A receptor, abolish synchronous activity in the hindbrain, while blockers of other neurotransmitter systems, including GABA and glutamate, do not. In addition, the 5-HT_2A receptor is expressed in the marginal regions in the entire medial-to-lateral extent of the hindbrain and in the midline commissural region. Thus, the serotonergic neurones of the developing midline raphe system may play a role in initiating and propagating spontaneous synchronous activity throughout the hindbrain.

(Received 29 April 2005; accepted after revision 31 May 2005; first published online 2 June 2005)
Corresponding author M. Bosma: Department of Biology, University of Washington, Seattle WA 98195-1800, USA. Email: martibee{at}u.washington.edu

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