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Preprodynorphin mRNA‐expressing neurones in the rat parabrachial nucleus: subnuclear localization, hypothalamic projections and colocalization with noxious‐evoked fos‐like immunoreactivity
Author(s) -
Hermanson Ola,
Telkov Miroslav,
Geijer Thomas,
Hallbeck Martin,
Blomqvist Anders
Publication year - 1998
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.1998.00021.x
Subject(s) - parabrachial nucleus , in situ hybridization , biology , colocalization , dynorphin , nucleus , neuroscience , nociception , noxious stimulus , c fos , messenger rna , gene expression , opioid peptide , opioid , gene , receptor , biochemistry
The dorsal lateral subnucleus of the rat pontine parabrachial nucleus is a major target for ascending nociceptive information from the spinal cord. With in situ hybridization histochemistry, using a radiolabelled cRNA probe, we demonstrate that neurones in and near the dorsal lateral subnucleus express preprodynorphin mRNA. The cRNA probe was constructed from a PCR product amplified from rat genomic DNA. Sequencing of the PCR product revealed that it corresponded to the sequence 466–1101 of the rat preprodynorphin gene exon 4. Tract tracing experiments, using injection of cholera toxin subunit B into the hypothalamic median preoptic nucleus, showed a retrograde labelling pattern of neurones in the parabrachial nucleus that was almost identical to that of the preprodynorphin mRNA expressing neurones. Double‐labelling, combining immunohistochemical detection of tracer and in situ hybridization, revealed that the retrogradely labelled neurones expressed preprodynorphin mRNA. A similar double‐labelling, combining in situ hybridization with immunohistochemical detection of noxious‐evoked fos following formalin injection into one hindpaw of awake animals, showed that almost all fos ‐immunoreactive neurones in the dorsal lateral parabrachial subnucleus also expressed preprodynorphin mRNA. Quantitative analysis suggested that the evoked fos immunoreactivity was accompanied by an increased preprodynorphin mRNA expression. The findings provide evidence that neurones in the dorsal lateral subnucleus produce dynorphin and project to the median preoptic nucleus, and that noxious stimulation in awake animals synaptically activates the dynorphinergic neurones in this subnucleus. These observations are consistent with the idea of a functional and chemical heterogeneity among different parabrachial subnuclei that serves to produce specific homeostatic responses to stimuli that changes the physiological status of the organism, including tissue damage.