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Published on: October 16, 2013
Differential behavioral sensitivity to carbon dioxide (CO2) inhalation in rats
Andrew Winter1, Rebecca Ahlbrand2, Devanshi Naik3
1Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, College of Medicine, Cincinnati, OH 45219, United States; Neuroscience Graduate Program, University of Cincinnati, College of Medicine, Cincinnati, OH 45219, United States.
Carbon dioxide (CO2) inhalation reveals strain-specific fear and anxiety responses in rats. CO2-sensitive strains show altered serotonin and norepinephrine neuron activity, offering insights into panic disorder mechanisms.
Area of Science:
- Neuroscience
- Behavioral Pharmacology
- Psychiatry
Background:
- Inhalation of carbon dioxide (CO2) is a known trigger for fear and anxiety, reliably inducing panic attacks in individuals with panic disorder.
- Individual sensitivity to CO2 varies significantly, with a suspected genetic component, but the underlying neurobiological mechanisms remain unclear.
- Preclinical models are crucial for understanding differential CO2 responsivity and its relation to anxiety and panic disorders.
Purpose of the Study:
- To investigate strain-dependent behavioral and neurobiological responses to carbon dioxide (CO2) inhalation in four distinct rat strains.
- To examine the role of serotonergic and noradrenergic systems in differential CO2 sensitivity.
- To identify potential preclinical models for studying the mechanisms of panic and anxiety disorders.
Main Methods:
- Assessed behavioral responses (immobility, rearing, grooming) to CO2 inhalation in Sprague-Dawley (SD), Wistar (W), Long Evans (LE), and Wistar-Kyoto (WK) rats.
- Quantified tryptophan hydroxylase 2 (TPH-2)-positive serotonergic neurons in the dorsal raphe nucleus (DR) subdivisions.
- Measured dopamine β hydroxylase (DβH)-positive noradrenergic neurons in the locus coeruleus (LC).
Main Results:
- Significant strain differences in CO2-evoked behaviors were observed, with LE and WK rats exhibiting higher immobility compared to W and SD rats.
- CO2-sensitive strains (LE, WK) showed reduced TPH-2-positive cell counts in the dorsal raphe ventrolateral (DRVL)-ventrolateral periaqueductal gray (VLPAG) subdivision.
- CO2-sensitive strains displayed higher DβH-positive cell counts in the locus coeruleus (LC).
Conclusions:
- Rat strain significantly influences behavioral and neurobiological responses to CO2 inhalation, indicating differential CO2 sensitivity.
- Alterations in central serotonergic and noradrenergic systems are associated with CO2 sensitivity, suggesting a role in panic and anxiety regulation.
- Comparative studies using CO2-vulnerable and resistant rat strains can advance the mechanistic understanding of panic and anxiety disorders.
