Burn edema reduction by methysergide is not due to control of regional vasodilation

5-HT2a receptor antagonism reduces burn-induced macromolecular efflux in rats

BACKGROUND

Major thermal injuries lead to a systemic inflammatory response with systemic capillary leakage and multiple organ dysfunction. This systemic inflammatory response is induced by a variety of immunmodulative molecules including TNFα and serotonin. Unspecific serotonin antagonism leads to reduced macromolecular efflux in rat mesenteries after burn plasma transfer. The aim of the present study was to evaluate the effect of specific 5-HT2a antagonism on early burn edema.

METHODS

Donor rats (DR) underwent thermal injury (100 °C water, 30% BSA, 12 s) for positive controls. For negative controls, DR underwent sham burn (37 °C water, 30% BSA, 12 s). DR plasma (harvested 4 h post-trauma) was transferred to healthy individuals for positive controls. Study rats received burn plasma (BP) and a Bolus injection of Ketanserin (Ket) (1 mg kg(-1) body weight). Negative controls underwent sham burn plasma infusion. Intravital microscopy was performed in mesenteric venules (0/60/120 min). Edema was assessed by FITC-albumin extravasation. Additionally, leukocyte rolling and sticking (cells mm(-2)) as well as microhemodynamic parameters were assessed.

RESULTS

Significant systemic capillary leakage was observed after BP transfer at 120 min and additional administration of Ket attenuated the postburn edema to sham burn levels. Ket also leads to significantly decreased leukocyte-endothelial interactions when compared to positive controls.

CONCLUSION

5-HT2a antagonism reduces plasma extravasation after burn plasma transfer in healthy individuals. The influence of leukocyte-endothelial interactions on postburn edema remains unclear.

Suppression of cortical spreading depression in migraine prophylaxis

OBJECTIVE

Topiramate, valproate, propranolol, amitriptyline, and methysergide have been widely prescribed for migraine prophylaxis, but their mechanism or site of action is uncertain. Cortical spreading depression (CSD) has been implicated in migraine and as a headache trigger and can be evoked in experimental animals by electrical or chemical stimulation. We hypothesized that migraine prophylactic agents suppress CSD as a common mechanism of action.

METHODS

Rats were treated either acutely or chronically over weeks and months, with one of the above migraine prophylactic drugs, vehicle, or D-propranolol, a clinically ineffective drug. The impact of treatment was determined on the frequency of evoked CSDs after topical potassium application or on the incremental cathodal stimulation threshold to evoke CSD.

RESULTS

Chronic daily administration of migraine prophylactic drugs dose-dependently suppressed CSD frequency by 40 to 80% and increased the cathodal stimulation threshold, whereas acute treatment was ineffective. Longer treatment durations produced stronger CSD suppression. Chronic D-propranolol treatment did not differ from saline control.

INTERPRETATION

Our data suggest that CSD provides a common therapeutic target for widely prescribed migraine prophylactic drugs. Assessing CSD threshold may prove useful for developing new prophylactic drugs and improving upon existing ones.