Central attenuation of baroreflex function during anaphylactic hypotension

Abstract

While some reports indicate that baroreceptor reflex and sympathetic output are centrally suppressed during anaphylactic hypotension, other reports that baroreflex function is enhanced, thus there is no clear consensus. This study examined the cardiovascular and sympathoexcitatory responses during an anaphylactic reaction in anesthetized rats. Anaphylactic hypotension induced by re-sensitization with Ovalbumin (OVA) significantly suppressed responses to the heart rate and sympathetic nerve activity in the early phase during the baroreceptor reflex. In addition, we investigated the medullary neuronal excitability related to the cardiovascular response during the anaphylactic reaction in conscious rats. In the OVA-sensitized group, heart rate was increased accompanying a marked decrease in blood pressure after re-sensitizing the administration of OVA in the conscious animals and this tachycardic response was significantly suppressed compared to the control group. And also, the excitability of neurons in the rostroventral medulla (RVM), the center of the baroreceptor reflex, was suppressed compared to the control group. Our results suggest that baroreceptor reflex function may be centrally suppressed during anaphylaxis-induced hypotension.