Absence of NK1 receptors in human blood lymphocytes and granulocytes

Substance P is a peptide that exerts its activity through the interaction with specific receptors that are distributed in different brain areas. Given the potential of NK1 receptor antagonists as antidepressants, the availability of a peripheral model of NK1 receptors would be particularly relevant for the possibility to perform studies in samples of patients. Therefore, with the present study we aimed to explore the possible existence of NK1 receptors by means of [3H]SR140333 and [125I]BHSP that behave as, respectively, antagonist and agonist, at this level, in human blood lymphocytes and granulocytes of healthy donors. The results of the present study failed to detect the presence of a high-affinity and saturable binding of [3H]SR140333 and [125I]BHSP in human blood cells, whereas a specific binding for both compounds was found in rat cerebral cortex that was used as the control tissue. These findings would question the presence of NK1 receptors in human circulating cells.