Co-localization of endomorphin-2 and substance P in primary afferent nociceptors and effects of injury: a light and electron microscopic study in the rat.

Endomorphin-2 (EM2) is a tetrapeptide with remarkable affinity and selectivity for the mu-opioid receptor. In the present study, we used double-fluorescence and electron microscopic immunocytochemistry to identify subsets of EM2-expressing neurons in dorsal root ganglia and spinal cord dorsal horn of adult rats. Within the lumbar dorsal root ganglia, we found EM2 immunoreactivity mainly in small-to-medium size neurons, most of which co-expressed the neuropeptide substance P (SP).

In vivo processing of LVV-hemorphin-7 in rat brain and blood utilizing microdialysis combined with electrospray mass spectrometry.

In vivo microdialysis in combination with liquid chromatography/electrospray time-of-flight mass spectrometry was used to study the processing of LVV-hemorphin-7, an endogenous decapeptide with opioid activity, in rat brain and blood. A microdialysis probe (flow rate 0.4 microL/min) was used to both introduce LVV-hemorphin-7 into the striatum of the brain (1.