Basal levels of plasma epinephrine and norepinephrine in the dog

Conscious (n = 62) and anesthetized (n = 34) dogs were studied to establish basal levels and ranges for plasma epinephrine (E) and norepinephrine (NE) in this species. Trained conscious dogs were familiarized to recording conditions and personnel for 2 to 3 weeks and acclimatized to the laboratory for at least 15 minutes prior to blood sampling from a chronically implanted catheter. Their basal values were 65 ± 47 pg/ml for E and 145 ± 58 pg/ml for NE, which were significantly lower (p < 0.05) than values in a second group of conscious dogs trained in the same manner but sampled soon after arrival to the laboratory (E = 144 ± 93 pg/ml; NE = 193 ± 86 pg/ml). Catecholamine levels in dogs anesthetized with one of three different regimes commonly used in cardiovascular studies were shown to be similar to the basal values found in conscious dogs acclimatized to the laboratory. The weak correlations found between basal plasma catecholamines and hemodynamic variables in all groups of conscious dogs reflect the complexity of factors interacting with the sympathetic nervous system in the maintenance of arterial pressure. These results document the variability that can be expected when using catecholamine levels as an index of sympathetic nervous system activity and the necessity of standardizing conditions for sample collection.