Continuous IV Infusion is the Choice Treatment Route for Arginine-vasopressin Receptor Blocker Conivaptan in Mice to Study Stroke-evoked Brain Edema

Summary

Our studies have revealed that the beneficial effects of conivaptan are dependent on the method of delivery after experimental stroke in mice. We have developed a research protocol for delivery of the receptor blocker via IV catheter on stroke-evoked brain edema formation in mice.

Abstract

Stroke is one of the major causes of morbidity and mortality in the world. Stroke is complicated by brain edema and other pathophysiological events. Among the most important players in the development and evolution of stroke-evoked brain edema is the hormone arginine-vasopressin and its receptors, V1a and V2. Recently, the V1a and V2 receptor blocker conivaptan has been attracting attention as a potential drug to reduce brain edema after stroke. However, animal models which involve conivaptan applications in stroke research need to be modified based on feasible routes of administration. Here the outcomes of 48 hr continuous intravenous (IV) are compared with intraperitoneal (IP) conivaptan treatments after experimental stroke in mice. We developed a protocol in which middle cerebral artery occlusion was combined with catheter installation into the jugular vein for IV treatment of conivaptan (0.2 mg) or vehicle. Different cohorts of animals were treated with 0.2 mg bolus of conivaptan or vehicle IP daily. Experimental stroke-evoked brain edema was evaluated in mice after continuous IV and IP treatments. Comparison of the results revealed that the continuous IV administration of conivaptan alleviates post-ischemic brain edema in mice, unlike the IP administration of conivaptan. We conclude that our model can be used for future studies of conivaptan applications in the context of stroke and brain edema.

Introduction

Stroke continues to be an enormous burden for patients and clinicians. Animal stroke models have been used in the laboratory setting for nearly two decades.¹ Nevertheless, experimental treatments that work in animals often fail in humans.² This discrepancy in treatment outcomes may be due to various factors, such as administration routes for drugs used in animal research, drug metabolism and elimination rate, and many other aspects. One of the major complications of stroke, brain edema, is a focus of current research in neuroscience. Mechanisms of brain edema formation involve disturbances in water and electrolyte balance triggered by the arginin....

Protocol

Experiments were carried out in accordance with the guidelines of the National Institutes of Health for the care and use of animals in research and were approved by the Swedish Medical Center Animal Care and Use Committee. All procedures were performed with appropriate aseptic techniques. Experimental animals utilized for the study were male, 3 months old, wild type C57 mice with body weight from 25 to 27 g.

1. In Vivo Stroke Induction

1. Pre-coat the Filament with Dental Resin Prior to the Surgery.
   1. Cut a 12 mm long piece of filament from a 7-0 nylon suture. Mix 2 parts of the resin with 1 part of the hardener,....

Results

Body temperature of the animals was within the physiological range and stable throughout the surgical procedure of stroke induction. Two mice that exhibited NDS lower than 2 immediately after MCAO were excluded from the study.

MCAO in mice produces infarct volume in the ipsilateral hemisphere at 48 hr. Evaluation of the TTC-stained slices shows that about 50% of the hemisphere is affected by infarct after MCAO (Figure 1D.......

Discussion

This study has important value for preclinical stroke research. This study reveals that continuous IV infusion of conivaptan (0.2 mg/day) after experimental stroke in mice efficiently reduces brain edema after 48 hr of treatment. The effect of IP injection of the same dose of conivaptan on brain edema was also investigated. Conivaptan treatment by both IV and IP routes produces aquaresis in mice as indicated by: 1) increase in plasma osmolality slightly above physiological levels; and 2) decrease in urine osmolality due .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Heated Pad	K&H Manufacturing Inc	1060
Temperature Monitor with Rectal Probe	Physitemp	7029
Silk Suture Spool, 6-0	Surgical Specialties Corporation	SP114
Silk Suture on a Needle, 3-0	Ethicon	1684G
Nylon Suture, 7-0	Ethicon	1696G
Dental Resin Polysiloxane with Hardener	Heraeus Kulzer	65817930
Microinfusion IV Pump	Kent Scietific	GT0897
Swivel 22GA	Instech	375/22PS
Laboratory Tubing, 0.94 mm x 0.51 mm	Dow Corning	508-002
Laboratory Tubing, 3.18 mm x 1.98 mm	Dow Corning	508-009