A human capsaicin model to quantitatively assess salivary CGRP secretion

Area of Science:

• Neuroscience
• Physiology
• Pharmacology

Background:

• Capsaicin, acting through the TRPV1 channel, stimulates calcitonin gene-related peptide (CGRP) release.
• Trigeminal nerve CGRP depletion after capsaicin suggests a link to nerve activation state.
• The study aimed to quantify CGRP release, determine optimal chili concentration, and assess response variability.

Purpose of the Study:

• To quantitatively measure CGRP release in saliva following oral capsaicin administration.
• To identify the optimal concentration of red chili homogenate for eliciting a CGRP response.
• To evaluate the day-to-day consistency of the CGRP release in response to capsaicin.

Main Methods:

• Saliva samples were collected from 13 healthy individuals over two consecutive days.
• Increasing concentrations of capsaicin (red chili homogenate) were applied orally.
• CGRP levels in saliva were measured and analyzed for dose-dependency and variability.

Main Results:

• Salivary CGRP secretion showed a significant dose-dependent increase with higher concentrations of red chili homogenate (p < 0.001).
• Undiluted homogenate yielded the highest CGRP levels compared to baseline (p = 0.003).
• The dose-dependent CGRP response was consistent across days, with no significant day-to-day variability observed (p > 0.14).

Conclusions:

• Oral red chili homogenate administration is well-tolerated and induces a reproducible, dose-dependent CGRP release in saliva.
• This method provides a non-invasive approach to assess the activation state of the trigeminal nerve innervating salivary glands.
• The findings support the use of salivary CGRP measurements as a reliable biomarker for trigeminal nerve activity.