Cerebral Cortex Advance Access originally published online on November 21, 2008
Cerebral Cortex 2009 19(8):1776-1786; doi:10.1093/cercor/bhn208
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Differences in Response to Serotonergic Activation between First and Higher Order Thalamic Nuclei
Department of Neurobiology, The University of Chicago, 947 E. 58th Street, Chicago, IL 60637, USA
Address correspondence to S. M. Sherman, PhD, Department of Neurobiology, The University of Chicago, 947 E. 58th Street, MC 0926, 316 Abbott, Chicago, IL 60637, USA. Email: msherman{at}bsd.uchicago.edu
Two types of thalamic nuclei have been recognized: first order, which relay information from subcortical sources, and higher order, which may relay information from one cortical area to another. We have recently shown that muscarinic agonists depolarize all first order and most higher order relay cells but hyperpolarize a significant proportion of higher order relay cells. We now extend this result to serotonergic agonists, using rat thalamic brain slices and whole-cell, current- and voltage-clamp recordings from relay cells in various first order (the lateral geniculate nucleus, the ventral posterior nucleus, and the ventral portion of the medial geniculate body) and higher order nuclei (the lateral posterior, the posterior medial nucleus, and the dorsal portion of the medial geniculate body). Similar to the effects of muscarinic agonists, we found that first and most higher order relay cells were depolarized by serotonergic agonists, but 15% of higher order relay cells responded with hyperpolarization. Thus different subsets of higher order relay cells are hyperpolarized by these modulatory systems, which could have implications for the transfer of information between cortical areas.
Key Words: burst • first order • higher order • modulator • serotonin • tonic