PROTOVERATRINE-A AND PROTOVERATRINE-B INCREASE SLEEP-APNEA INDEX IN SPRAGUE-DAWLEY RATS

The action of protovertarines A and B, which stimulate carotid sinus b aroreceptors and vagal sensory endings in the heart as well as pulmona ry bed, were assessed on spontaneous and postsigh central sleep apneas in freely moving Sprague-Dawley rats. During the 6-h recording period , animals were simultaneously monitored for sleep by using electroence phalogram and electromyogram recordings, for respiration by single-cha mber plethysmography, and for blood pressure and heart period by using radiotelemetry. After administration of 0.2, 0.5, or 1 mg/kg sc of pr otoveratrines, cardiopulmonary changes lasting at least 6 h were obser ved in all three behavioral states [heart period increased up to 23% i n wakefulness, 21% in non-rapid-eye-movement (non-REM) sleep, and 20% in REM sleep; P < 0.005 for each]. At the same time, there was a subst antial increase in the number of spontaneous (375% increase; P = 0.04) and postsigh (268% increase, P = 0.0002) apneas. Minute ventilation d ecreased by up to 24% in wakefulness, 25% in non-REM, and 35% in REM s leep (P < 0.05 for each). We conclude that pharmacological stimulation of baroreflexes promotes apnea expression in the sleeping rat.