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Projections from nucleus raphe obscurus to the periaqueductal grey matter in the rat
F M Semenenko1, B M Lumb, T A Lovick
1Department of Physiology, University of Bristol, UK.
Abstract:
Retrograde transport of rhodamine- or coumarin-labelled latex microspheres was used to investigate projections from nucleus raphe obscurus (NRO) to the periaqueductal grey matter (PAG) in rats. Few labelled neurones (3.5 +/- 1.2; mean +/- S.E.M.) were seen in NRO after injections of microspheres into the dorsolateral and lateral PAG (n = 11) but after injections into the ventrolateral sector (n = 9), significant numbers (42.6 +/- 8.1) were present, particularly in the rostral third of NRO (66% of labelled cells). The results suggest that the projection from NRO to the PAG is restricted to the ventrolateral sector. Any influence of NRO on the dorsal PAG must therefore be mediated indirectly.