Understanding rat emotional responses to CO₂

Area of Science:

• Neuroscience
• Animal Behavior
• Psychopharmacology

Background:

• Carbon dioxide (CO2) exposure is a common procedure, but its impact on animal welfare and emotional states requires thorough understanding.
• Previous research suggests CO2 can be aversive, but a comprehensive summary of rat emotional responses is lacking.

Purpose of the Study:

• To review and synthesize existing evidence on the emotional experiences of rats during carbon dioxide exposure.
• To compare rat responses to CO2 with human experiences and the effects of pharmacological interventions.

Main Methods:

• Systematic review of behavioral, physiological, and neurobiological studies on rat responses to CO2.
• Analysis of data on plasma corticosterone levels, bradycardia, and defense behaviors.
• Examination of the counteracting effects of anxiolytics, serotonin reuptake inhibitors (SRIs), and selective serotonin reuptake inhibitors (SSRIs).

Main Results:

• CO2 exposure is consistently aversive to rats, eliciting active and passive defense behaviors.
• Physiological markers such as increased plasma corticosterone and bradycardia were observed.
• Anxiolytics, SRIs, and SSRIs mitigated CO2-induced responses in rats, mirroring effects in humans experiencing anxiety, fear, and panic.

Conclusions:

• Behavioral, physiological, and neurobiological evidence supports that carbon dioxide exposure induces negative emotions in rats.
• The findings highlight the importance of considering CO2's aversive nature in experimental design and animal welfare.
• Neurobiological mechanisms involving hypercapnia, acidosis, and key brain regions/neurotransmitters are activated by CO2 exposure.