Physiological significance of the defense response to intense auditory stimulation: a pharmacological blockade study.
This paper examines through pharmacological blockade some questions related to the physiological significance of the defense response to intense auditory stimulation. Nine subjects received intravenous metoprolol (10-15 mg i.v.), intravenous atropine (0.03 mg/kg i.v.), or a saline solution as placebo condition before undertaking a test of the defense response to a distorted sound of 400 Hz frequency, 109 dB intensity, 0.5 sec duration and virtually instantaneous risetime. Dependent variables were continuous (beat-to-beat) heart rate, stroke volume and blood pressure. The results suggest: (1) a vagal origen of the first acceleration and first deceleration and a sympathetic-parasympathetic interaction during the second acceleration and second deceleration of the heart rate response; (2) a blood pressure response pattern characterized by an increase during the first heart rate deceleration (4-11 sec), a posterior decrease coinciding with the second heart rate acceleration (from 12 to 37 sec), and a lighter increase during the second heart rate deceleration (from 38 to 63 sec); and (3) an implication of the baroreceptor reflex, including a baroreceptor mediated inhibition of the parasympathetic cardiac activity during the second accelerative component of the cardiac response.
Reyes del Paso
G A
GA
Departamento de Psicología, Facultad de Humanidades, Universidad de Jaén, Spain.
Vila
J
J
García
A
A
D000161:Acoustic Stimulation; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000328:Adult; D001285:Atropine / Q000494:pharmacology; D017704:Baroreflex / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D004562:Electrocardiography / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects* / Q000502:physiology*; D006801:Humans; D013318:Stroke Volume / Q000187:drug effects
D000319:Adrenergic beta-Antagonists; D001285:Atropine