Plasma cortisol response cannot be classically conditioned in a taste-endocrine paradigm in humans

Area of Science:

• Neuroendocrinology
• Behavioral Science
• Psychoneuroimmunology

Background:

• Associative learning can modify peripheral immune responses.
• The capacity for classical conditioning of neuroendocrine parameters is less understood.
• This study explores behavioral conditioning of endocrine responses in humans.

Purpose of the Study:

• To behaviorally condition endocrine responses using a modified taste-endocrine paradigm.
• To investigate if a conditioned stimulus (CS) can elicit a learned endocrine response.
• To examine the role of corticotropin-releasing hormone (CRH) in conditioned responses.

Main Methods:

• A randomized, double-blind study with 31 healthy males.
• Participants received a flavored drink (CS) paired with CRH or placebo (unconditioned stimulus, US).
• Plasma cortisol, noradrenaline, heart rate, and psychological state were measured post-injection.

Main Results:

• CRH administration significantly increased cortisol, noradrenaline, heart rate, and anxiety.
• Re-exposure to the CS alone did not condition significant neuroendocrine responses.
• A subgroup with high baseline cortisol showed increased cortisol on evocation days.

Conclusions:

• The taste-CRH paradigm did not successfully condition cortisol release as a learned endocrine response.
• Higher baseline cortisol levels might facilitate conditioned cortisol responses.
• Further research is needed to clarify the role of baseline cortisol in conditioning.