Background and Purpose-Critical factors influencing the neuroprotective efficacy of postischemic hypothermia include depth, duration, and time of onset of cooling. In clinical practice, there is an unavoidable lag between the hypoxic-ischemic (HI) insult and the opportunity to initiate cooling. We hypothesized that early administration of a neuroprotective agent in combination with later-onset cooling could represent an effective therapeutic intervention after neonatal HI. We evaluated whether treatment with topiramate, a clinically available anticonvulsant, increased the efficacy of delayed post-HI hypothermia in a neonatal rat stroke model. Methods-Postnatal day 7 (P7) rats underwent right carotid artery ligation followed by 1.5 hours of exposure to 8%oxygen. Fifteen minutes post-HI, animals received injections of topiramate (30 mg/kg) or PBS. Cooling was initiated 3 hours later ("delayed hypothermia") in all animals (3 hours, in 27°C incubator). Functional outcome (forepaw response to vibrissae stimulation) and pathology (morphometric lesion measurements) were evaluated at P15 and P35. Results-Neither topiramate nor delayed hypothermia alone conferred protection in this protocol. Combined treatment with topiramate and delayed hypothermia improved both performance and pathological outcome in P15 and P35 rats compared with PBS-treated animals that underwent delayed hypothermia concurrently. At P15, functional measures were better in topiramate-treated animals (mean correct forepaw response 9.3/10 versus 4.8/10; PϽ0.001), and there was Ͼ50% reduction in tissue loss (PϽ0.001); trends were similar at P35. Conclusions-Our data provide the impetus for further evaluation of therapeutic approaches that combine drug therapy with delayed-onset cooling after neonatal HI brain injury.

Seizures are associated with adverse outcome in infants with hypoxic-ischemic encephalopathy. We hypothesized that early administration of the anticonvulsant phenobarbital after cerebral hypoxia ischemia could enhance the neuroprotective efficacy of delayed-onset hypothermia. We tested this hypothesis in a neonatal rodent model. Seven-d-old rats (n ϭ 104) underwent right carotid ligation, followed by 90 min 8% O 2 exposure; 15 min later, they received injections of phenobarbital (40 mg/kg) or saline. One or 3 h later, all were treated with hypothermia (30°C, 3 h). Function and neuropathology were evaluated after 7 d (early outcomes) or 1 mo (late outcomes). Early outcome assessment demonstrated better sensorimotor performance and less cortical damage in phenobarbital-treated groups; there were no differences between groups in which the hypothermia delay was shortened from 3 to 1 h. Late outcome assessment confirmed sustained benefits of phenobarbital ϩ hypothermia treatment; sensorimotor performance was better (persistent attenuation of contralateral forepaw placing deficits and absence of contralateral forepaw neglect); neuropathology scores were lower (median, phenobarbital 2 and saline 8.5, p Ͻ 0.05); and less ipsilateral cerebral hemisphere %Damage (mean Ϯ SD, 11 Ϯ 17 versus 28 Ϯ 22, p Ͻ 0.05). These results suggest that early posthypoxia-ischemia administration of phenobarbital may augment the neuroprotective efficacy of therapeutic hypothermia. T he results of four clinical trials support the safety and efficacy of hypothermia to decrease death and disability in infants with hypoxic-ischemic encephalopathy (HIE) (1-4). However, in these trials Ͼ40% of hypothermia-treated infants died or had poor neurologic outcomes. Thus, there is a need for strategies to improve the neuroprotective efficacy of hypothermia. One possible approach is to combine hypothermia with pharmacotherapy.In experimental models of neonatal hypoxic-ischemic brain injury, several agents enhance the neuroprotective efficacy of hypothermia; these include topiramate, an anticonvulsant (5); xenon, an anesthetic (6); and N-acetylcysteine, an antioxidant (7). There is minimal neonatal clinical experience with these drugs (8). Nevertheless, many neuroactive drugs are commonly administered to encephalopathic neonates, and an important question is whether any of these drugs could augment hypothermic neuroprotection.Anticonvulsants are an attractive group of drugs to study in combination with hypothermia. Many have neuroprotective properties in cerebral ischemia models, although it is uncertain whether these effects are attributable to seizure cessation (9). Seizures are common in encephalopathic neonates, in whom they may exacerbate hypoxic-ischemic brain injury (10,11). In one hypothermia trial, seizures were an independent predictor of adverse outcome (12). Phenobarbital is currently the anticonvulsant used most commonly to treat neonatal seizures (13). Moreover, in a small randomized trial, treatment of infants with HIE with phenobarb...

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The neonatal rat model of unilateral cerebral hypoxia-ischemia (HI) is commonly used to test the efficacy of therapeutic strategies for prevention or treatment of stroke in the immature brain. Traditionally neuroprotection has been defined as reduction in tissue injury; there is growing interest in complementary functional assessment. Our objectives were to determine whether lateralizing performance deficits could be detected in two sensorimotor tests not previously used after neonatal HI, and to determine whether performance reflected the extent of tissue damage. Seven-day-old rats that underwent right carotid ligation followed by 1.5 h in 8% O₂ and age-matched controls were tested for sensorimotor performance on postnatal day 35 (P35). We evaluated initial forepaw placement on the wall of a cylinder, and time taken to contact and remove adhesive stickers from the dorsum of each forepaw. Cortical, striatal and hippocampal damage severity was evaluated on P36 by calculating the contralateral-ipsilateral percent difference in regional areas. There was an inverse relationship between cortical and striatal damage severity and percent contralateral forepaw initiation in the cylinder. There was a direct linear relationship between damage severity and the delay from contact to removal of the contralateral sticker. These two tests revealed quantifiable contralateral sensorimotor deficits 4 weeks after unilateral neonatal cerebral HI in animals with cortical and striatal damage.

Lee RH, Liu YQ, Chen PY, Liu CH, Chen MF, Lin HW, Kuo JS, Premkumar LS, Lee TJ. Sympathetic ␣3␤2-nAChRs mediate cerebral neurogenic nitrergic vasodilation in the swine. Am J Physiol Heart Circ Physiol 301: H344 -H354, 2011. First published May 2, 2011; doi:10.1152/ajpheart.00172.2011.-The ␣7-nicotinic ACh receptor (␣7-nAChR) on sympathetic neurons innervating basilar arteries of pigs crossed bred between Landrace and Yorkshire (LY) is known to mediate nicotine-induced, ␤-amyloid (A␤)-sensitive nitrergic neurogenic vasodilation. Preliminary studies, however, demonstrated that nicotine-induced cerebral vasodilation in pigs crossbred among Landrace, Yorkshire, and Duroc (LYD) was insensitive to A␤ and ␣-bungarotoxin (␣-BGTX). We investigated nAChR subtype on sympathetic neurons innervating LYD basilar arteries. Nicotine-induced relaxation of porcine isolated basilar arteries was examined by tissue bath myography, inward currents on nAChR-expressing oocytes by two-electrode voltage recording, and mRNA and protein expression in the superior cervical ganglion (SCG) and middle cervical ganglion (MCG) by reverse transcription PCR and Western blotting. Nicotine-induced basilar arterial relaxation was not affected by A␤, ␣-BGTX, and ␣-conotoxin IMI (␣7-nAChR antagonists), or ␣-conotoxin AuIB (␣3␤4-nAChR antagonist) but was inhibited by tropinone and tropane (␣3-containing nAChR antagonists) and ␣-conotoxin MII (selective ␣ 3␤2-nAChR antagonist). Nicotine-induced inward currents in ␣ 3␤2-nAChR-expressing oocytes were inhibited by ␣-conotoxin MII but not by ␣-BGTX, A␤, or ␣-conotoxin AuIB. mRNAs of ␣ 3-, ␣7-, ␤2-, and ␤4-subunits were expressed in both SCGs and MCGs with significantly higher mRNAs of ␣ 3-, ␤2-, and ␤ 4-subunits than that of ␣7-subunit. The A␤-insensitive sympathetic ␣ 3␤2-nAChR mediates nicotine-induced cerebral nitrergic neurogenic vasodilation in LYD pigs. The different finding from A␤-sensitive ␣ 7-nAChR in basilar arteries of LY pigs may offer a partial explanation for different sensitivities of individuals to A␤ in causing diminished cerebral nitrergic vasodilation in diseases involving A␤.␣ 3␤2-nicotinic ACh receptor; axo-axonal interaction; ␤-amyloid; cerebral perivascular sympathetic nerves; superior cervical ganglion IT IS WELL ESTABLISHED THAT cerebral arteries receive dense sympathetic innervation originating in the superior cervical ganglion (SCG) (24, 50) and that nicotinic ACh receptors (nAChRs) on the nerve terminals regulate norepinephrine (NE) release (50). In the pigs crossbred between Landrace and Yorkshire in the United States, activation by nicotinic agonists of the nAChRs on perivascular sympathetic nerves innervating cerebral arteries results in release of NE, which then causes release of nitric oxide (NO) from the nearby parasympathetic nitrergic nerves and dilation of the arteries (22, 39). This nicotinic agonist-induced axo-axonal interaction leading to nitrergic vasodilation is mediated by the ␣ 7 -nAChR subtype (39). The vasodilation is blocked by ␤-amyloid peptide (A␤) via inhib...