Experimental model for investigating hyponatremia after subarachnoid hemorrhage in rats

Human Albumin Improves Long-Term Behavioral Sequelae After Subarachnoid Hemorrhage Through Neurovascular Remodeling

OBJECTIVE

Subarachnoid hemorrhage results in significant long-lasting neurologic sequelae. Here, we investigated whether human albumin improves long-term outcomes in experimental subarachnoid hemorrhage and whether neurovascular remodeling is involved in the protection of albumin.

DESIGN

Laboratory investigation.

SETTING

Hospital research laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Rats underwent subarachnoid hemorrhage by endovascular perforation. Albumin of either 0.63 or 1.25 g/kg was injected IV immediately after the surgery. Modified Garcia test, beam-walking test, novel object recognition, and Morris water maze were employed to determine the behavioral deficits. The effects of albumin on early neurovascular dysfunction and chronic synaptic plasticity were also studied.

MEASUREMENTS AND MAIN RESULTS

Both doses of albumin significantly improved the sensorimotor scores (F = 31.277; p = 0.001) and cognitive performance (F = 7.982; p = 0.001 in novel object recognition test; and F = 3.431; p = 0.026 in the latency analysis of Morris water maze test) for at least 40 days after subarachnoid hemorrhage. There were remarkable microvasculature hypoperfusion, intracranial pressure rise, early vasoconstriction, neural apoptosis, and degeneration in subarachnoid hemorrhage rats, with albumin significantly attenuating such neurovascular dysfunction. Furthermore, albumin markedly prevented blood-brain barrier disruption, as indicated by less blood-brain barrier leakage, preserved blood-brain barrier-related proteins, and dampened gelatinase activities. The expressions of key synaptic elements were up-regulated with albumin supplementation in both acute and chronic phases. Accordingly, a higher dendritic spine density was observed in the prefrontal and hippocampal areas of albumin-treated subarachnoid hemorrhage animals.

CONCLUSIONS

Albumin at low-to-moderate doses markedly improves long-term neurobehavioral sequelae after subarachnoid hemorrhage, which may involve an integrated process of neurovascular remodeling.

Long-term functional consequences and ongoing cerebral inflammation after subarachnoid hemorrhage in the rat

Subarachnoid hemorrhage (SAH) represents a considerable health problem with an incidence of 6–7 per 100.000 individuals per year in Western society. We investigated the long-term consequences of SAH on behavior, neuroinflammation and gray- and white-matter damage using an endovascular puncture model in Wistar rats. Rats were divided into a mild or severe SAH group based on their acute neurological score at 24 h post-SAH. The degree of hemorrhage determined in post-mortem brains at 48 h strongly correlated with the acute neurological score. Severe SAH induced increased TNF-α, IL-1β, IL-10, MCP-1, MIP2, CINC-1 mRNA expression and cortical neutrophil influx at 48 h post-insult. Neuroinflammation after SAH was very long-lasting and still present at day 21 as determined by Iba-1 staining (microglia/macrophages) and GFAP (astrocytes). Long-term neuroinflammation was strongly associated with the degree of severity of SAH. Cerebral damage to gray- and white-matter was visualized by immunohistochemistry for MAP2 and MBP at 21 days after SAH. Severe SAH induced significant gray- and white-matter damage. MAP2 loss at day 21 correlated significantly with the acute neurological score determined at 24 h post-SAH. Sensorimotor behavior, determined by the adhesive removal task and von Frey test, was affected after severe SAH at day 21. In conclusion, we are the first to show that SAH induces ongoing cortical inflammation. Moreover, SAH induces mainly cortical long-term brain damage, which is associated with long-term sensorimotor damage.

Development of an experimental model to study the pathophysiology of cerebral salt wasting following subarachnoid hemorrhage

Hyponatremia is frequent following cranial -neurosurgery or acute brain injury like subarachnoid hemorrhage (SAH), and increases mortality by 30%. The patho-physiology is not understood nor does a causal therapy exist. Since clinical trials are potentially dangerous in this very ill population, we examined whether an established rat model allows studying cerebral salt wasting (CSW) following SAH. The daily urine sodium excretion as well as plasma sodium, osmolality and antidiuretic hormone (ADH) levels were measured for 10 days. Following the injection of 300 μl of blood into the great cistern (SAH(severe)), natriuresis peaked twice (days 1 and 3-5, p < 0.05) resulting in a plasma sodium nadir (day 1 - 133.9 mmol/L, day 5 - 132.6 mmol/L), while following the injection of 300 μL saline (ICP(control)), natriuresis occurred delayed on days 4-5 (p < 0.05). Following double SAH (200 μL twice, 24 h apart), a natriuresis on day 4 resulted in a hyponatremia (131.7 mmol/L, p = 0.025). Neither SAH(mild) (100 μL), the injection of hemolyzed blood (100 μL) or hypertonic saline (200 μL) replicated the effect. The immediate release of ADH (32.23 ± 34.87 pg/mL) following SAH(severe) normalized over the next few days. We conclude that first, the rat model of SAH is suitable for studying CSW, second the increase in intracranial pressure generates the delayed hyponatremia, and third, the ADH release does not mediate natriuresis.