Abstract
Purpose: :
Neurotensin receptor agonists have analgesic activity on the corneal surface. Our purpose was to characterize the expression of neurotensin receptors in the cornea and trigeminal ganglion on which these agonists likely act.
Methods: :
Total mRNA was isolated from mouse corneal and trigeminal tissues and subjected to RT-PCR (trigeminal tissue)using primers specific for neurotensin receptor-1 (NTR1), receptor-2 (NTR2), or receptor-3 (NTR3) and Taqman qPCR (trigeminal and corneal tissues) comparing the expression of these receptors to their expression in whole brain tissue. Protein extracts from corneal and trigeminal ganglion tissue were analyzed via western blotting for NTR1-3. Immunohistochemistry was performed on tissue sections from trigeminal ganglion using rabbit anti-NTR antibodies with secondary detection via anti-rabbit Cy3 conjugated antibodies. Sections were imaged using an Axiovert 200m fluorescence miscroscope equipped with a digital camera.
Results: :
Non-quantitative RT-PCR revealed detectable levels of NTR1-3 in trigeminal tissues. However, qPCR demonstrated the substantial differences in expression levels of NTRs in trigeminal neurons with NTR3>NTR2>NTR1, while in corneal tissue, the differences in expression was NTR3>NTR1 (no NTR2 was detected). Protein expression analysis via western blotting mirrored the relative expression levels seen by qPCR. Immunolocalization of low levels of NTR1 and high levels of NTR3 were seen in trigeminal neurons. No NTR2 was detected via immunohistochemistry.
Conclusions: :
We have identified significant levels of NTR expression in both the trigeminal ganglion and cornea via qPCR, western blotting, and immunohistochemistry, providing potential sites of action for neurotensin agonists which possess topical analgesic properties.
Keywords: cornea: basic science • signal transduction • receptors