Effects of the novel NMDA antagonists CP-98,113, CP-101,581 and CP-101,606 on cognitive function and regional cerebral edema following experimental brain injury in the rat.

The present study evaluated the effects of two novel N-methyl-D-aspartate (NMDA) receptor blockers and ifenprodil derivatives, CP-101,606 and CP-101,581, and their racemic mixture CP-98,113, on spatial memory and regional cerebral edema following experimental fluid-percussion (FP) brain injury in the rat (n = 66). Fifteen minutes after brain injury (2.5 atm), animals received either (1) CP-98,113 (5 mg/kg, i.p., n = 11), (2) CP-101,581 (5 mg/kg, i.p., n = 13), (3) CP-101,606 (6.5 mg/kg, i.p., n = 12), or (4) DMSO vehicle (equal volume, n = 12); followed by a continuous 24-h subcutaneous infusion of drug at a rate of 1.5 mg/kg/h by means of miniature osmotic (Alzet) pumps implanted subcutaneously. Control (uninjured) animals were subjected to identical anesthesia and surgery without injury and received DMSO vehicle (n = 8); CP-98,113 (5 mg/kg, i.p., n = 3); CP-101,581 (5 mg/kg, i.p., n = 3); or CP-101,606 (6.5 mg/kg, i.p., n = 3). FP brain injury produced a significant cognitive impairment assessed at 2 days postinjury using a well-characterized testing paradigm of visuospatial memory in the Morris Water Maze (MWM) (p < 0.001). Administration of either CP-98,113, CP-101,581, or CP-101,606 had no effect on sham (uninjured) animals, but significant attenuated spatial memory impairment assessed at 2 days postinjury (p = 0.004, p = 0.02, or p = 0.02, respectively). Administration of CP-89,113 but not CP-101,581 or CP-101,606 significantly reduced the extent of regional cerebral edema in the cortex adjacent to the site of injury (p < 0.05) and in the ipsilateral hippocampus (p < 0.05) and thalamus (p < 0.05). These results suggest that excitatory neurotransmission may play a pivotal role in the pathogenesis of memory dysfunction following traumatic brain injury (TBI) and that blockade of the NMDA receptor may significantly attenuate cognitive deficits associated with TBI.

(S)-emopamil attenuates acute reduction in regional cerebral blood flow following experimental brain injury.

We examined the effects of (S)-emopamil, a phenylalkylamine calcium channel blocker with serotonin receptor antagonist properties, on regional cerebral blood flow (rCBF) following experimental brain injury in the rat. Animals were subjected to fluid percussion brain injury of moderate severity (2.1 atm), and received (S)-emopamil (20 mg/kg, i.p., n = 10) or saline (n = 10) at 20 minutes postinjury and 2.5 hours after the first injection of the drug. Consecutive rCBF measurements were performed: (1) prior to injury, (2) 15 minutes, (3) 90 minutes, and (4) 4 hours postinjury, using the radiolabeled microsphere technique. Brain injury produced an acute and significant reduction of rCBF at 15 minutes postinjury in all the regions examined (p < 0.05). At 90 minutes postinjury, rCBF remained significantly depressed in the forebrain regions. All brain regions showed a recovery of rCBF to normal by 4 hours following injury in saline-treated animals, with the exception of injured left parietal cortex and bilateral hippocampi, where rCBF remained significantly depressed. A significant attenuation of the trauma-induced reduction in rCBF was observed at 70 minutes after the first administration of (S)-emopamil in the forebrain regions and cerebellum (p < 0.05). Following the second (S)-emopamil injection, the significant improvement in rCBF observed in left injured cortex was maintained. These results suggest that (S)-emopamil may be efficacious in reversing post-traumatic alterations in rCBF, which may contribute to the post-traumatic pathophysiologic sequelae.

Evaluation of memory dysfunction following experimental brain injury using the Morris water maze.

Memory dysfunction, a common clinical feature of traumatic brain injury (TBI), is thought to be related to secondary damage of key anatomic structures in the brain, including the hippocampus. In the present study, we have characterized and evaluated a novel experimental paradigm using the Morris water maze (MWM) technique, to measure post-TBI memory retention after lateral (parasagittal) fluid percussion (FP) brain injury in rats. Male Sprague-Dawley rats (n = 37) received a total of 20 training trials over 2 days in the MWM. Two and a half hours after the last training trial, the animals received FP brain injury of moderate severity (2.3 atmospheres, n = 12), high severity (2.6 atm, n = 13), or no injury (n = 12). Forty-two hours after FP brain injury, we observed a highly sufficient memory dysfunction in animals from both injury groups compared to the uninjured group (p less than 0.001). The degree of memory dysfunction was found to be directly related to the severity of injury, with the high severity group scoring significantly worse than the moderately injured group (p = 0.15). In addition, hippocampal cell loss was observed after brain injury, but only unilaterally. These data suggest that lateral FP brain injury causes memory dysfunction possibly related to concurrent hippocampal cell loss and that posttraumatic memory deficits may be sensitively quantitated using the memory testing paradigm described.

Effects of the NMDA antagonist CP-98,113 on regional cerebral edema and cardiovascular, cognitive, and neurobehavioral function following experimental brain injury in the rat.

The present study examined the effects of CP-98,113, an N-methyl-d-aspartate (NMDA) receptor blocker, on cardiovascular variables, neurobehavioral motor function, spatial memory deficits, and cerebral edema formation following lateral (parasagittal) fluid-percussion (FP) brain injury in the rat. In Study 1, we compared the cardiovascular effects of i.p. administration of CP-98, 113 at 15 min postinjury at doses of 1 mg/kg, 2 mg/kg, 5 mg/kg, or 20 mg/kg (n=8/dose). Animals receiving 1 mg/kg to 5 mg/kg CP-98,113 showed slight but nonsignificant decreases in blood pressure, while those receiving the highest dose (20 mg/kg) showed significant hypotension. Based upon those observations, the 5 mg/kg dose was chosen as the optimal dose for subsequent behavioral studies. In Study 2, 15 min following lateral FP brain injury of moderate severity (2.5 atm), animals randomly received either CP-98,113 (5 mg/kg, i.p., n=23) followed by a 24-h subcutaneous infusion (1.5 mg kg-1 h-1) by means of a miniature osmotic pump, or identical volume of vehicle (n=24), and were evaluated for neurologic motor function (n=11/drug vs. 11/vehicle), memory function, and cerebral edema (n=12/drug vs. 13/vehicle). CP-98,113 (5 mg/kg) significantly attenuated neurologic motor dysfunction at 24 h (p<0.01) and 2 weeks (p<0.05) postinjury, reduced posttraumatic impairment in spatial memory observed at 48 h postinjury (p<0.001), and significantly reduced focal brain edema in the cortex adjacent to the site of maximal injury at 48 h postinjury (injury penumbra) (p<0.001). These results suggest that blockade of the NMDA receptor may attenuate the deleterious sequelae of traumatic brain injury.

Magnesium and ketamine attenuate cognitive dysfunction following experimental brain injury.

We evaluated the therapeutic effects of two noncompetitive antagonists of the N-methyl-D-aspartate (NMDA) receptor, MgCl2 and ketamine, both individually and together, on cognitive dysfunction observed following parasagittal fluid-percussion (FP) brain injury in the rat. Using a modified Morris water maze technique, we found significant attenuation of post-traumatic memory dysfunction in animals treated with either MgCl2 (125 mumol) or ketamine (4 mg/kg) (P < 0.005). Combined MgCl2 and ketamine treatment also preserved memory function (P < 0.005), with no apparent additive effect.

Evaluation of a novel calcium channel blocker, (S)-emopamil, on regional cerebral edema and neurobehavioral function after experimental brain injury.

The authors investigated the effects of a novel calcium channel blocker, (S)-emopamil, on cerebral edema and neurobehavioral and memory function following experimental fluid-percussion brain injury in the rat. Two independent experiments were performed to evaluate the effects of this compound on cardiovascular variables and postinjury cerebral edema (increases in tissue water content), and on cognitive deficits and neurological motor function following brain injury. Treatment with (S)-emopamil significantly reduced focal brain edema at 48 hours after brain injury. Profound memory dysfunction induced by brain injury was significantly attenuated following (S)-emopamil treatment. In addition, (S)-emopamil also attenuated the deficits in motor function that were observed over a 2-week period following brain injury. These results suggest that changes in calcium homeostasis may play an important role in the pathogenesis of trauma to the central nervous system and that the calcium channel blocker (S)-emopamil might be a useful compound for the treatment of traumatic brain injury.

[MR imaging of traumatic cerebellar dysfunction].

Four cases of cerebellar dysfunction following head trauma are presented. Cerebellar signs revealed were those such as dysmetria, dysdiadochokinesis, horizontal nystagmus and ataxia. T2-weighted magnetic resonance (MR) imaging (0.15 tesla, spin-echo method; TR 2000 msec. and TE 100 msec.) revealed focal lesions in these patients, although CT scan failed to demonstrate any changes in the cerebellum. The cerebellar symptoms were maximal immediately after the trauma but improved gradually in two cases. These are compatible with the transient traumatic cerebellar dysfunction postulated by R. C. Cantu in 1969. The pathophysiology of this syndrome, whether it is due to cerebellar concussion or contusion, has not yet been determined. The abnormality of the cerebellum revealed by MR imaging seemed to be contusion rather than concussion. Therefore the authors presume that transient traumatic cerebellar dysfunction is caused by minor cerebellar contusion. In the other two cases, delayed epidural hemorrhage ensued and the symptoms disappeared rapidly after evacuation of the hematoma. In these patients, occurrence of delayed epidural hematoma in the posterior cranial fossa was predicted by MR imaging. The authors regard the lesion as an alarm signal indicating the probable occurrence of infratentorial hematoma.

Measurement of hippocampal levels of cellular second messengers following in situ freezing.

The in situ freezing technique has been widely used to fix labile metabolites and cellular second messengers in cerebral cortex. In this study, we isolated specific brain regions at 0 degree C from coronal sections of frozen heads following in situ brain freezing and measured regional concentrations of labile metabolites and cellular messengers. These levels in the cortex were compared with those in cortical punches obtained at freezing temperature (less than -40 degrees C) from the same in situ frozen brains and those of cortex dissected from decapitated animals. In both isoflurane- and pentobarbital-anesthetized animals, we observed that the levels of lactate, free fatty acids, inositol 1,4,5-trisphosphate, and diacylglycerol, as well as the proportion of protein kinase C associated with the membrane fraction, were similar in cortical punches taken at freezing temperature and those dissected at 0 degree C. However, with animals decapitated at room temperature, cortical and hippocampal levels of lactate, free fatty acids, and inositol 1,4,5-trisphosphate and the proportion of membrane protein kinase C were significantly higher than those of corresponding brain regions isolated at 0 degree C from in situ frozen brains (p < 0.05). These results indicate that dissection of cortex and hippocampus at 0 degree C following in situ freezing will eliminate decapitation-induced production of artifacts and changes in the levels of cellular second messengers such as inositol 1,4,5-trisphosphate, diacylglycerol, and protein kinase C. The present technique, used in conjunction with in situ freezing, will fix cellular second messengers and labile metabolites in several regions of brain and may facilitate accurate characterization of molecular and cellular mechanisms underlying CNS function.

Effects of the excitatory amino acid receptor antagonists kynurenate and indole-2-carboxylic acid on behavioral and neurochemical outcome following experimental brain injury.

The overactivation of the NMDA receptor is thought to be a major contributor to the pathophysiologic sequelae of traumatic brain injury (TBI), which commonly includes memory dysfunction. Uniquely, potentiation of the NMDA receptor is dependent on the binding of glycine to a distinct site on the receptor. Despite the potential role of the NMDA receptor in the development of post-TBI cognitive deficits, no studies to date have evaluated the efficacy of NMDA receptor antagonists on memory dysfunction after brain injury. Moreover, glycine site antagonists have not been employed as potential therapeutic agents in models of TBI. In the present study, we evaluated the effects of two glycine site antagonists, kynurenate (KYNA) and indole-2-carboxylic acid (I2CA), on memory and motor dysfunction, cerebral edema formation, and changes in regional total tissue brain [Na], [K], [Ca], [Mg], and [Zn], following lateral fluid-percussion brain injury in the rat. We found that both KYNA (300 mg/kg) and I2CA (50 mg/kg and 20 mg/kg) administered 15 min postinjury dramatically attenuated trauma-induced cognitive dysfunction (p < 0.01). In addition, both compounds improved neurologic motor deficits measured at 2 weeks following injury (p < 0.05). KYNA (300 mg/kg) reduced edema in the cortex, hippocampus, and thalamus, while I2CA (20 mg/kg) reduced edema formation only in the thalamus. Differential effects of KYNA and I2CA on cation concentrations were also noted. KYNA attenuated the postinjury increase in regional tissue [Ca]; however, it had little effect on other cation concentrations. I2CA reversed the postinjury regional increases in [Na] and decreases in [K], [Mg], and [Zn], but had little effect on [Ca] changes. These results indicate that KYNA and I2CA may have differential, but beneficial effects on both behavioral and neurochemical sequelae of TBI.

The sodium channel blocker and glutamate release inhibitor BW1003C87 and magnesium attenuate regional cerebral edema following experimental brain injury in the rat.

Excitatory amino acid (EAA) neurotransmitters may play a role in the pathophysiology of traumatic injury to the CNS. Although NMDA receptor antagonists have been reported to have therapeutic efficacy in animal models of brain injury, these compounds may have unacceptable toxicity for clinical use. One alternative approach is to inhibit the release of EAAs following traumatic injury. The present study examined the effects of administration of a novel sodium channel blocker and EAA release inhibitor, BW1003C87, or the NMDA receptor-associated ion channel blocker magnesium chloride on cerebral edema formation following experimental brain injury in the rat. Animals (n = 33) were subjected to fluid percussion brain injury of moderate severity (2.3 atm) over the left parietal cortex. Fifteen minutes after injury, the animals received a constant infusion of BW1003C87 (10 mg/kg, i.v.), magnesium chloride (300 mumol/kg, i.v.), or saline over 15 min (2.75 ml/kg/15 min). In all animals, regional tissue water content in brain was assessed at 48 h after injury, using the wet weight/dry weight technique. In saline-treated control animals, fluid percussion brain injury produced significant regional brain edema in injured left parietal cortex (p < 0.001), the cortical area adjacent to the site of maximal injury (p < 0.001), left hippocampus (p < 0.001), and left thalamus (p = 0.02) at 48 h after brain injury. Administration of BW1003C87 15 min postinjury significantly reduced focal brain edema in the cortical area adjacent to the site of maximal injury (p < 0.02) and left hippocampus (p < 0.01), whereas magnesium chloride attenuated edema in left hippocampus (p = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)