Effect of PACAP on Heat Exposure

Area of Science:

• Physiology
• Neuroendocrinology
• Climate Change Biology

Background:

• Heat stroke is a severe illness exacerbated by rising global temperatures.
• Pituitary adenylate cyclase-activating polypeptide (PACAP) is involved in thermoregulation, but its specific role in heat stress is not fully understood.

Purpose of the Study:

• To investigate the role of PACAP in the physiological response to heat stress.
• To determine if PACAP knockout mice exhibit altered thermoregulation and survival under heat exposure.

Main Methods:

• PACAP knockout (KO) and wild-type ICR mice were exposed to high heat (36°C, 99% humidity).
• Survival rates, body temperatures, and c-Fos expression in the hypothalamus were measured.
• Differences in brown adipose tissue (heat production site) were analyzed.

Main Results:

• PACAP KO mice demonstrated significantly higher survival rates and maintained lower body temperatures compared to wild-type mice.
• Reduced c-Fos gene expression and immunoreaction were observed in the hypothalamus of PACAP KO mice.
• Distinct differences in brown adipose tissue activity were noted between PACAP KO and wild-type mice, suggesting altered heat production.

Conclusions:

• Mice lacking PACAP are more resistant to heat exposure, indicating PACAP contributes to heat sensitivity.
• PACAP influences thermoregulation and survival during heat stress, potentially via hypothalamic pathways and brown adipose tissue activity.
• These findings highlight a novel role for PACAP in the body's response to extreme heat, relevant to climate change adaptation.