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This Article Full Text Full Text (PDF) All Versions of this Article: 566/3/929    most recent jphysiol.2005.086520v1 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 Voisin, D. L Articles by Dallel, R Search for Related Content PubMed PubMed Citation Articles by Voisin, D. L Articles by Dallel, R

¹ Inserm E216 Neurobiologie de la douleur trigéminale, Faculté de Chirurgie Dentaire, 11 boulevard Charles de Gaulle, 63000 Clermont-Ferrand, France; Université Clermont1, 63000 Clermont-Ferrand, France

In the thalamus, noradrenergic output from the pontine nucleus locus coeruleus (LC) may actively shape the response properties of various sensory networks en route to the cortex. Little is known, however, about the involvement of ascending noradrenergic innervation of the somatosensory thalamus in the processing of nociceptive information. To address this question, we combined the study of Fos expression upon nociceptive tooth pulp stimulation in the anaesthetized rat, with the detection of retrogradely traced neurones from the somatosensory thalamus. Cell bodies labelled retrogradely from the left thalamus were observed on both sides of the LC, with an ipsilateral predominance (n = 8). Electrical stimulation of the right incisor pulp (n = 4) provoked a significantly stronger Fos expression (around twice) than sham surgery (n = 4), in both the ipsi- and contralateral LC. Significantly larger numbers of double labelled neurones were counted in the LC of tooth-pulp-stimulated animals (representing around 30% of retrogradely labelled cells in LC) than in the LC of sham animals. They were found bilaterally, but with a clear, significant, ipsilateral (i.e. left) predominance. The present data offer an anatomical framework to understand how the LC is involved in the sensory processing of nociceptive information in the thalamus. For the first time, it is shown that nociceptive stimulation activates LC neurones projecting to the somatosensory thalamus. This suggests a new role for LC in modulating nociception within the thalamus.

(Received 11 March 2005; accepted after revision 16 May 2005; first published online 19 May 2005)
Corresponding author D. L. Voisin: Inserm E216 Neurobiologie de la douleur trigéminale, Faculté de Chirurgie Dentaire, 11 boulevard Charles de Gaulle, 63000 Clermont-Ferrand, France. Email: daniel.voisin{at}u-clermont1.fr

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