A panic attack-like unusual stress reaction

Area of Science:

• Neuroscience
• Psychiatry
• Endocrinology

Background:

• The hypothalamus-pituitary-adrenal (HPA) axis activation is a hallmark of stress.
• Panic attacks, despite psychological stress, paradoxically show a lack of HPA axis response.
• Dorsal periaqueductal gray matter (DPAG) stimulation induces defensive behaviors, modeling panic attacks.

Purpose of the Study:

• To investigate plasma levels of corticotropin and prolactin following DPAG-evoked freezing and flight behaviors in rats.
• To determine if intense emotional arousal and physical exertion during fear-like behaviors impact stress hormone levels.
• To explore the role of DPAG in panic attacks by examining its effect on the HPA axis.

Main Methods:

• Rats with electrodes in the DPAG and intra-atrial catheters were stimulated.
• Blood samples were collected before, immediately after, and up to 27 hours post-stimulation.
• Plasma hormone levels were measured using immunoassays and compared to resting or restraint-stressed rats.

Main Results:

• DPAG-evoked freezing and flight behaviors did not alter plasma levels of stress hormones (corticotropin and prolactin).
• Prolonged DPAG stimulation (5 min) at flight threshold intensity did not significantly change corticotropin levels.
• This study provides the first evidence of absent stress hormone responses during intense fear-like behaviors in rats.

Conclusions:

• The lack of HPA axis activation during DPAG-evoked fear behaviors challenges the traditional view of stress response.
• Data support the hypothesis that DPAG is involved in spontaneous panic attacks, potentially bypassing the canonical stress pathway.
• Findings contribute to understanding the neurobiological underpinnings of panic attacks and their dissociation from the typical stress response.