title: Influence of atrial mechanoreceptors upon the sympathetic efferent activity elicited during a cardiogenic chemoreflex in the dog.
abstract: Two different cardiogenic reflexes were studied for their effects upon the activity recorded from the thoracic cardiac nerves of 7 chloralose-anesthetized dogs. Sympathetic efferent activity in 5 right and 7 left anterior ansa multifiber preparations was quantitatively analyzed. A cardiogenic hypertensive chemoreflex was induced by administration of serotonin (100 micrograms/ml, 2 ml) into the left atrium before, during and after inflation of balloons in the right and/or left atrial appendages. Balloon inflations alone resulted in heart rate increases of 5-20 bpm but arterial blood pressure, pulse pressure and end diastolic pressure were not significantly affected. Control serotonin-induced efferent discharges were 174 +/- 10% (mean +/- S.E.M.) of resting activity with a duration of 5.2 +/- 0.4 s. During inflation of both atrial balloons, the serotonin-induced efferent discharges were 165 +/- 14% (N.S.) of resting activity with a duration of 7.8 +/- 0.7 s (P less than 0.01). Following release of the balloons, the serotonin-induced discharges were 152 +/- 17% (N.S.) of resting activity with a duration of 4.9 +/- 0.4 s (N.S.). These results suggest that afferent signals from atrial mechanoreceptors can act to increase the duration but not the total intensity of the efferent sympathetic discharges elicited during a cardiogenic chemoreflex.
mesh_terms: D000818:Animals; D001794:Blood Pressure; D004285:Dogs; D005260:Female; D006321:Heart / Q000294:innervation*; D006325:Heart Atria; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology*; D013564:Sympathetic Nervous System / Q000502:physiology*
chemical_list: D012701:Serotonin