Variability of hemodynamic values and plasma catecholamine concentrations over a one-hour period in conscious, restrained rats

Restrained conscious rats have been widely used for physiological and pharmacological hemodynamic studies. In this condition, the variability of the circulation is unclear. Repeated measurements in restrained normal rats showed stable systemic hemodynamics (cardiac output ranging from 130 ± 14 to 174 ± 10, mean arterial pressure ranging from 109 ± 9 to 117 ± 5 mmHg) and splanchnic hemodynamics (splanchnic blood flow ranging from 8.51 ± 1.89 to 13.01 ± 1.45 mL min⁻¹ 100 g⁻¹ body wt) over a period of 1 hr. Slight but not significant hemodynamic variations, however, occurred in pulmonary blood flow. Similarly, plasma noradrenaline concentrations did not vary over this period (plasma noradrenaline level ranging from $\text{186 ± 36}\text{to}\text{358 ± 64}\text{pg}\text{mL}$). These plasma noradrenaline concentrations were similar to those measured in a group of conscious unrestrained rats 3 hr after recovery from surgery ($\text{292 ± 60}\text{pg}\text{mL}$). A significant correlation was observed between plasma noradrenaline concentration and heart rate.