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Midline serotonergic neurones contribute to widespread synchronized activity in embryonic mouse hindbrain
Author(s) -
Hunt Peter N.,
McCabe Annette K.,
Bosma Martha M.
Publication year - 2005
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2005.089581
Subject(s) - hindbrain , serotonergic , neuroscience , midbrain , biology , raphe , raphe nuclei , serotonin , anatomy , central nervous system , receptor , biochemistry
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.