The role of 5‐hydroxytryptamine in the feline response to intravenous infusion of live E. coli

Abstract

A standardized septic shock was induced in cats by intravenous infusion of a live E. coli bacteria strain. The bacterial infusion induced a rapid haemodynamic response characterized mainly by a pulmonary arterial hypertension and a late phase characterized by systemic hypotension and hypodynamic circulation. Systemic arterial, pulmonary arterial, portal venous, left atrial pressures, max inspiratory‐expiratory pressure difference in the trachea, aortic and intestinal blood flows were monitored. Arterial blood samples were taken for recording the number of circulating platelets and white blood cells and for determining the acid‐base balance. The effect of pretreatment with ketanserin, a specific 5‐hydroxytryptamine2 (5‐HT2)‐receptor blocker on these haemodynamic reactions was studied. In short term experiments on non‐bacteriaemic control cats, ketanserin prevented the pulmonary hypertension induced by intravenous 5‐HT infusions but not the increase in intestinal blood flow. Ketanserin induced a reduction of total peripheral (including intestinal) vascular resistance to blood flow but had no effect on aortic blood flow. After infusion of bacteria, ketanserin pretreated cats were more hypotensive due to a relative peripheral dilatation of the resistance vessels. Ketanserin pretreatment had no effect on the pulmonary vascular reactions, the tracheal pressure difference or the number of circulating platelets or white blood cells. Thus, except for a more pronounced hypotension early after bacterial infusion, ketanserin pretreatment did not influence the haemodynamic response. It is concluded that 5‐HT is not of significant importance in the pathogenesis of the haemodynamic reactions following experimental bacteraemia.

Opening the Microcirculation with Ketanserin I.V. Improves Peripheral Temperature: An Observational Cohort Study

“…Though vasodilatation must have occurred, there is no increase in the infusion of fluids when comparing the first three hours before with three hours after start of ketanserin. This is in accordance with previous experimental study where splanchnic and other perfusion increased without increasing aortic flow [24].…”

Ketanserin

“…This vasoconstrictor response can be reversed by ketanserin (250,278). Likewise, in anesthetized dogs and cats the increase in vascular resistance of femoral and pulmonary arteries in response to serotonin is antagonized by ketanserin, whereas the dilatation of small vessels is not (7,10,23,173). A study in anesthetized pigs also showed that ketanserin blocks the reduction by serotonin of total carotid blood flow and enhances serotonin-induced arteriolar vasodilatation (283).…”

Effects of Dihydroergotamine on the Feline Cardiovascular Response to Intravenous Infusion of Live <i>Escherichia coli</i>Bacteria

“…This lack of Table IV. Grade of damage in the small intestinal mucosa influence on the response to the standardized bacteremia [5] has for ketanserin been dem onstrated earlier in a similar experimental model [2].…”