# A study of salivary cortisol and glutamate after the cold pressor task in healthy adults

## TL;DR

This study examines how salivary cortisol and glutamate levels change in healthy adults after a cold pressor task, finding that cortisol increases significantly while glutamate does not show consistent changes.

## Contribution

The study provides new insights into the usefulness of salivary cortisol as a biomarker for acute pain and highlights the limitations of glutamate in this context.

## Key findings

- Salivary cortisol levels significantly increased 10 minutes after the cold pressor task.
- Male participants showed a greater cortisol increase compared to females.
- Salivary glutamate levels did not show statistically significant changes except at t = +50 minutes.

## Abstract

Nociception related salivary biomolecules can be a useful future aid in the assessment of acute pain. We have investigated changes in the levels of two salivary biomolecules, glutamate and cortisol, following the induction of acute cold pain using the cold pressor task (CPT). Saliva samples were collected from 18 healthy volunteers before, immediately after and then, every 10 minutes for one hour after CPT. Statistical analysis of the biomolecule concentrations across all participants and time points were done. This showed significant differences between salivary cortisol concentration before (median 0.14 µg/dL, Interquartile Range (IQR) = 0.1) and 10 minutes after termination of CPT (median 0.34 µg/dL, IQR = 0.4, p = 0.007). Male participants exhibited a greater increase in cortisol concentration after cold pain compared to females. The timeline and pattern of the rise in salivary cortisol concentration in this study are consistent with existing literature. Salivary glutamate concentration fluctuated but none of the changes were statistically significant except at t =  + 50 minutes, when the concentration had dropped below baseline. The findings do not support the use of glutamate as a useful biomarker in acute pain despite evidence that plasma and salivary glutamate levels are higher in people with chronic pain conditions such as migraine and temporomandibular disorder.