The effect of streptomycin on the carotid baroreflex was examined in 23 anesthetized rats with isolated carotid sinus perfusion. The results obtained are as follows. (1) By perfusing the isolated carotid sinus with streptomycin (100 micromol/L) the functional curve of baroreflex was shifted to the right and upward with its peak slope (PS) decreasing from 0.40+/-0.01 to 0.33+/-0.01 kPa (P<0.001), and the reflex decrease in the mean arterial pressure (RD) was lowered from 6.22+/-0.13 to 5.02+/-0.11 kPa (P<0.001), while the threshold pressure (TP), equilibrium pressure (EP) and saturation pressure (SP) were significantly increased from 8.27+/-0.25 to 10.33+/-0.32 kPa (P<0.01), 12.71+/-0.21 to 13.33+/-0.30 kPa (P<0.01) and 24.41+/-0.14 to 26.11+/-0.28 kPa (P<0.01),respectively. Among the functional parameters of carotid baroreflex, the changes in RD, PS and TP induced by streptomycin were dose-dependent. (2) By perfusing the isolated carotid sinus with adenosine (125 micromol/L), carotid baroreflex was facilitated. Pretreatment with streptomycin (200 micromol/L) not only eliminated the facilitated effect of ado on carotid baroreflex but also caused a reflex decrease in MAP to a level lower than control. Taken together, it is suggested that streptomycin can markedly inhibit the carotid sinus baroreflex in anesthetized rats.