Autonomic cardiovascular responses to smoke exposure in conscious rats

and the change in renal sympathetic nerve activity (RSNA) in response to smoke exposure were investigated in unrestrained conscious rats. Smoke exposure caused a prominent increase in RSNA (to 557.3 & 221.9 % of the control level) and plasma norepinephrine [from 0.18 t 0.08 (control) to 0.66 * 0.22 rig/ml (at peak response of smoke exposure)], a slight increase in arte-rial blood pressure (from 89.6 t 3.3 to 103.6 t 3.8 mmHg), and marked bradycardia (from 386.6 k 12.8 to 231.3 & 20.6 beats/min). Respiratory rate in conscious rats was initially increased (from 1.6 t 0.1 to 6.1 & 0.3 breaths/s) but was decreased (to 0.9 t 0.1 breaths/s) at the peak phase of the cardiovascular responses to smoke inhalation. Blood gases and pH reflected these changes in respiratory rate to some extent. Sinoaortic denervation did not attenuate the bradycardia (from 402 & 17.5 to 255.8 k 16.2 beats/min) or increase in RSNA (t