Caspase-dependent cell death involved in brain damage after acute subdural hematoma in rats

Traumatic brain injury is associated with acute subdural hematoma (ASDH) that worsens outcome. Although early removal of blood can reduce mortality, patients still die or remain disabled after surgery and additional treatments are needed. The blood mass and extravasated blood induce pathomechanisms such as high intracranial pressure (ICP), ischemia, apoptosis and inflammation which lead to acute as well as delayed cell death. Only little is known about the basis of delayed cell death in this type of injury. Thus, the purpose of the study was to investigate to which extent caspase-dependent intracellular processes are involved in the lesion development after ASDH in rats. A volume of 300microL blood was infused into the subdural space under monitoring of ICP and tissue oxygen concentration. To asses delayed cell death mechanisms, DNA fragmentation was measured 1, 2, 4 and 7 days after ASDH by TUNEL staining, and the effect of the pan-caspase inhibitor zVADfmk on lesion volume was assessed 7 days post-ASDH. A peak of TUNEL-positive cells was found in the injured cortex at day 2 after blood infusion (53.4+/-11.6 cells/mm(2)). zVADfmk (160ng), applied by intracerebroventricular injection before ASDH, reduced lesion volume significantly by more than 50% (vehicle: 23.79+/-7.62mm(3); zVADfmk: 9.06+/-4.08). The data show for the first time that apoptotic processes are evident following ASDH and that caspase-dependent mechanisms play a crucial role in the lesion development caused by the blood effect on brain tissue.

Acute and late changes in N-acetyl-aspartate following diffuse axonal injury in rats: an MRI spectroscopy and microdialysis study

N-acetyl-aspartate (NAA) measured by proton nuclear magnetic resonance spectroscopy (1H-NMR) has been used as a marker of neuronal injury in many cerebral pathologies. Therefore, we evaluate the roles of microdialysis vs. 1H-NMR as techniques to assess NAA (NAAd; NAA/Creatine ratio) in the living brain, and compare the results with whole brain NAA (NAAw), analyzed by HPLC after diffuse traumatic brain injury (TBI). Acute (4 h post-injury survival) and late (48 h survival) changes were studied in a sham-operated group (Sham, n = 4), and two injured groups (TBI/4 h, n = 8; TBI/48 h, n = 7). Baseline NAAd was 8.17 +/- 1 microM, and there was no significant difference between groups. There was only a small (twice of control), but transient increase in NAAd in the TBI/4 h group after trauma. Baseline NAA/Cr ratio was 1.35 +/- 0.2, which did not change significantly between baseline, 1, 2, 3, 4 and 48 h or between groups after TBI. Whole brain NAAw (baseline 8.5 +/- 0.5 mmol kg-1 wet weight) did not differ significantly between groups before and after TBI. Diffuse TBI did not produce long-term changes in NAA, assessed by three different methods. These results may indicate that NAA is not a sensitive marker of the severity of diffuse axonal damage. However, further studies are needed to evaluate whether confounding factors such as microdialysis probe, voxel position and non-regional tissue homogenization might have influenced our data.

The neuroprotective effect of a new serotonin receptor agonist, BAY X3702, upon focal ischemic brain damage caused by acute subdural hematoma in the rat

We tested the neuroprotective effect of a novel, high affinity serotonin (5-HT1A) agonist, BAY X3702, in a rat model of acute subdural hematoma (ASDH). Animals were treated with 0.01 mg/kg (n=8), 0.003 mg/kg (n=8) BAY X3702 or vehicle (n=4) 15 min before (i.v.) and after (continuous infusion) injection of 400 microl of autologous blood into the subdural space. The ischemic brain damage at 4 h after ASDH was 59.01+/-39 and 60.8+/-49 mm(3) for the low- and high-dose BAY X3702 group, respectively, which was significantly smaller compared to the vehicle-treated ASDH group (106.2+/-33 mm(3)). The result indicates that this novel, high affinity 5-HT(1A) agonist, BAY X3702, is neuroprotective in this model.

6-(alkylamino)-9-alkylpurines. A new class of potential antipsychotic agents

A series of 6-(alkylamino)-9-alkylpurines was synthesized and evaluated for the property of antagonizing the behavioral effects in animals of the dopamine agonist apomorphine. This model for identifying potential antipsychotic agents is based on the hypothesis that agents that antagonize apomorphine-induced aggressive behavior in rats and apomorphine-induced climbing in mice, but that do not block stereotyped behavior, could have an antipsychotic effect in humans without producing extrapyramidal side effects. The antiaggressive-behavior activity of lead compound 1 (6-(dimethylamino)-9-(3-phenylalaninamidobenzyl)-9H-purine) was improved 48-fold with 6-(cyclopropylamino)-9-(cyclopropylmethyl)-2-(trifluoromethyl)-9H- purine (80) (po ED50 of 2 mg/kg), which was obtained through an iterative sequence of structure--activity relationship studies that encompassed evaluation of the effects of structure variations at the purine 9-, 6-, and 2-positions. Potency was enhanced with a 9-cyclopropyl group, the duration of action was improved with the 6-(cyclopropylamino) substituent, potency was further enhanced with an N-formyl prodrug, and an agent with reduced cardiovascular effect emerged with the 2-trifluoromethyl purine 80. This potential antipsychotic agent was not developed further due to undesirable effects on the stomach.