Pain mechanismNeurochemical characterization of neuronal populations expressing protein kinase C gamma isoform in the spinal cord and gracile nucleus of the rat
Section snippets
Experimental procedures
All animal procedures were carried out in accordance with the UK Home Office Scientific Procedures Act (1986). Efforts were made to minimize the number of animals used and their suffering. A total of 24 rats were used in the present study. Ten adult Wistar rats were overdosed with sodium pentobarbital and perfused through the ascending aorta with 50 ml saline followed by 400 ml 4% paraformaldehyde in 0.1 M phosphate buffer at pH 7.4. The brainstem region containing the dorsal column nuclei and
General distribution of PKCγ in the medulla
PKCγ cells have been reported in the medullary dorsal horn of the spinal trigeminal nucleus and in the cochlear nucleus (Li et al 2001a, Li et al 2001b, Tanaka and Saito 1992). We also observed immunopositive neurons within these regions but also within the para-trigeminal and lateral reticular nuclei. Rostral to the obex of the medulla, especially strong terminal labeling was seen in the vestibular nuclei. Positive fibers were also seen in the corticospinal and trigeminal tracts and the medial
Discussion
Our study demonstrates the following new findings with regard to PKCγ neurons: Firstly, we have identified and characterized a population of neurons within the gracile nucleus in terms of neurotransmitter receptors and shown that a proportion project to the thalamus. Secondly, we show that some of these cells are capable of eliciting c-fos expression after peripheral nerve injury using c-fiber strength electrical stimulation. Thirdly, in the spinal cord, we have further characterized the PKCγ
Conclusion
In conclusion, this study has furthered the knowledge of PKCγ expressing cells by showing that more than 80% of spinal cord neurons expressed either the GluR1 or GluR2/3 AMPA receptor subunits, with a differential lamina distribution. Although PKCγ cells are known to play a role in chronic pain conditions little is known about the direct synaptic contacts to these cells. We suggest that glutamatergic input is likely to be very important, either from primary afferents or from local excitatory
Acknowledgments
This work was supported by the Wellcome Trust. A.S.H. was also the recipient of a Wellcome Trust Summer Vacation Scholarship.
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