Responses of single‐unit carotid body chemoreceptors in adult rats

1 Our goal was to describe the in situ responses in rats of single-unit carotid body chemoreceptors to changes in arterial P_O2 and P_CO2. We identified single-unit carotid chemoreceptor activity in male, adult Sprague-Dawley rats by their rapid responses to i.v. NaCN (20 μg) and transient (10 s) asphyxia. 2 Single-unit chemoreceptor responses to isocapnic changes in oxygenation within the arterial oxygen pressure range 34-114 mmHg were described by the power function: f_dis= 74010(P${}_{\text{a,O}{}_{\text{2}}}$)^−2.5; (r²= 0.6), where f_dis is the discharge frequency (spikes s⁻¹), P${}_{\text{a,O}{}_{\text{2}}}$ is the arterial oxygen partial pressure (mmHg) and r² is the correlation coefficient. 3 The responses to iso-oxic changes in CO₂, assumed to be linear, had a slope of 0.089 spikes s⁻¹ (mmHg P_a,CO2)⁻¹ (r²= 0.7). 4 We conclude that carotid body chemoreceptors in adult rats have responses to changes in P${}_{\text{a,O}{}_{\text{2}}}$ and P_a,CO2 similar to those of other species.