Association between thermal response and endogenous dopamine: Step-change environments in winter

Area of Science:

• Human Physiology
• Environmental Science
• Neuroscience

Background:

• Transient thermal environments, characterized by temperature step changes, are common and impact human physiological and psychological responses.
• Understanding the interplay between subjective thermal perception and objective physiological markers is crucial for assessing comfort and regulation in dynamic conditions.

Purpose of the Study:

• To investigate the association between subjective thermal sensation vote (TSV), thermal comfort vote (TCV), mean skin temperature (MST), and endogenous dopamine (DA) in a step-change thermal environment.
• To explore the influence of seasonal variations on thermal perception during transient temperature changes.

Main Methods:

• Three distinct temperature step changes (I3, I9, I15) were implemented, involving transitions from 15°C to higher temperatures and back.
• Sixteen healthy subjects (8 male, 8 female) reported their TSV and TCV.
• Mean skin temperature (MST) from six body parts and endogenous dopamine (DA) levels were measured.

Main Results:

• Seasonal factors influenced the typical inverted U-shaped relationship between TSV/TCV and temperature, with winter experiencing a shift towards warmer sensations.
• A distinct association was observed between dimensionless dopamine (DA*), MST, and TSV: DA* exhibited a U-shaped change with exposure time when MST ≤ 31°C and TSV was -2 or -1, but increased with exposure time when MST > 31°C and TSV was 0, 1, or 2.
• Higher DA concentrations correlated with states of thermal nonequilibrium and enhanced autonomous thermal regulation.

Conclusions:

• Endogenous dopamine levels appear linked to the body's heat storage and autonomous thermal regulation mechanisms during transient thermal exposures.
• Increased dopamine concentration may signify heightened human physiological responses to thermal nonequilibrium and stronger regulatory demands.
• This research provides insights into human thermoregulation mechanisms within dynamic environmental settings.