Contra lateral effects of unilateral stimuli

Objectives: Within the trigeminal nervous system, there is a clear linkage between peripheral and central changes in neurogenic activity. A pro-inflammatory stimulus, unilaterally injected into the masseter muscle, creates a bilateral response. The aim of this study was to elucidate if there is a difference in the contra-lateral response in CGRP-LI activity in the masseter muscle of different mammals, after unilateral stimulus. Methods: Either SD rats or porcine pigs were given a pro-inflammatory stimuli into the masseter muscle on one side. Biopsies were taken from the masseter muscles. Concentrations of calcitonin gene-related peptide like immunoreactivity (CGRP-LI) were analyzed with radio immune assay (RIA). SPSS software 10.0 was used for statistical comparison of relative differences between SD rats and porcine pigs. Results: The concentration of CGRP-LI was higher contra- lateral after unilateral stimuli, both in SD rats and in porcine pigs. However, no differences were found in between SD rats and porcine pigs, when comparing the relative difference between the corresponding masseter muscles. Conclusions: A higher contra-lateral concentration of CGRP-LI in the masseter muscle, after unilateral pro-inflammatory stimuli, can be seen as a host-defense mechanism. The contra- lateral response, likely mediated by the trigeminal nuclei, suggest that unilateral conditions are mirrored.