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Despite treatment with therapeutic hypothermia, almost 50% of infants with neonatal encephalopathy still have adverse outcomes. Additional treatments are required to maximize neuroprotection. Melatonin is a naturally occurring hormone involved in physiological processes that also has neuroprotective actions against hypoxic-ischaemic brain injury in animal models. The objective of this study was to assess neuroprotective effects of combining melatonin with therapeutic hypothermia after transient hypoxia-ischaemia in a piglet model of perinatal asphyxia using clinically relevant magnetic resonance spectroscopy biomarkers supported by immunohistochemistry. After a quantified global hypoxic-ischaemic insult, 17 newborn piglets were randomized to the following: (i) therapeutic hypothermia (33.5°C from 2 to 26 h after resuscitation, n = 8) and (ii) therapeutic hypothermia plus intravenous melatonin (5 mg/kg/h over 6 h started at 10 min after resuscitation and repeated at 24 h, n = 9). Cortical white matter and deep grey matter voxel proton and whole brain (31)P magnetic resonance spectroscopy were acquired before and during hypoxia-ischaemia, at 24 and 48 h after resuscitation. There was no difference in baseline variables, insult severity or any physiological or biochemical measure, including mean arterial blood pressure and inotrope use during the 48 h after hypoxia-ischaemia. Plasma levels of melatonin were 10 000 times higher in the hypothermia plus melatonin than hypothermia alone group. Melatonin-augmented hypothermia significantly reduced the hypoxic-ischaemic-induced increase in the area under the curve for proton magnetic resonance spectroscopy lactate/N-acetyl aspartate and lactate/total creatine ratios in the deep grey matter. Melatonin-augmented hypothermia increased levels of whole brain (31)P magnetic resonance spectroscopy nucleotide triphosphate/exchangeable phosphate pool. Correlating with improved cerebral energy metabolism, TUNEL-positive nuclei were reduced in the hypothermia plus melatonin group compared with hypothermia alone in the thalamus, internal capsule, putamen and caudate, and there was reduced cleaved caspase 3 in the thalamus. Although total numbers of microglia were not decreased in grey or white matter, expression of the prototypical cytotoxic microglial activation marker CD86 was decreased in the cortex at 48 h after hypoxia-ischaemia. The safety and improved neuroprotection with a combination of melatonin with cooling support phase II clinical trials in infants with moderate and severe neonatal encephalopathy.

We have previously demonstrated that ibotenate (IBO) injected into the pedunculopontine tegmental nucleus (PPTg) damages all neurones there while quinolinate (QUIN) makes relatively selective lesions of cholinergic neurones. We now compare the effects of two anaesthetics, sodium pentobarbitone and Avertin (tribromoethanol/tert-amylalcohol dissolved in ethanol, saline and phosphate buffer) on three doses of IBO and QUIN in the PPTg. Diaphorase-positive cell loss after QUIN was attenuated under barbiturate, the relative selectivity of QUIN for diaphorase-positive neurones was lost and lesion volumes were uniformly small compared with lesions made under Avertin anaesthesia. IBO toxicity was unaffected by anaesthesia. These data are discussed with reference to the actions of excitotoxins at glutamate receptor subtypes and interactions of barbiturates with the GABAA receptor.

Neuronal mechanisms underlying alcohol intoxication are unclear. We find that alcohol impairs motor coordination by enhancing tonic inhibition mediated by a specific subtype of extrasynaptic GABA(A) receptor (GABAR), alpha6beta3delta, expressed exclusively in cerebellar granule cells. In recombinant studies, we characterize a naturally occurring single-nucleotide polymorphism that causes a single amino acid change (R100Q) in alpha6 (encoded in rats by the Gabra6 gene). We show that this change selectively increases alcohol sensitivity of alpha6beta3delta GABARs. Behavioral and electrophysiological comparisons of Gabra6(100R/100R) and Gabra6(100Q/100Q) rats strongly suggest that alcohol impairs motor coordination by enhancing granule cell tonic inhibition. These findings identify extrasynaptic GABARs as critical targets underlying low-dose alcohol intoxication and demonstrate that subtle changes in tonic inhibition in one class of neurons can alter behavior.

Alcoholic patients who have undergone multiple detoxifications/relapses show altered processing of emotional signals. We performed functional magnetic resonance imaging during performance of implicit and explicit versions of a task in which subjects were presented with morphs of fearful facial emotional expressions. Participants were abstaining, multiply detoxified (MDTx; n=12) or singly detoxified patients (SDTx; n=17), and social drinker controls (n=31). Alcoholic patients were less able than controls to recognize fearful expressions, and showed lower activation in prefrontal areas, including orbitofrontal cortex and insula, which mediate emotional processing. The decrease in activation was greater in MDTx patients who also showed decreased connectivity between insula and prefrontal areas, and between amygdala and globus pallidus. In the explicit condition, the strength of connectivity between insula and areas involved in regulation of emotion (inferior frontal cortex and frontal pole) was negatively correlated with both the number of detoxifications and dependency (measured by the severity of alcohol dependency (SADQ) and control over drinking score (Impaired Control questionnaire, ICQ)). In contrast, increased connectivity was found between insula and the colliculus neuronal cluster, and between amygdala and stria terminalis bed nucleus. In the implicit condition, number of detoxifications and ICQ score correlated positively with connectivity between amygdala and prefrontal cortical areas involved in attentional and executive processes. Repeated episodes of detoxification from alcohol are associated with altered function both in fear perception pathways and in cortical modulation of emotions. Such changes may confer increased sensitivity to emotional stress and impaired social competence, contributing to relapse.

Drug and alcohol dependence are global problems with substantial societal costs. There are few treatments for relapse prevention and therefore a pressing need for further study of brain mechanisms underpinning relapse circuitry. The Imperial College Cambridge Manchester (ICCAM) platform study is an experimental medicine approach to this problem: using functional magnetic resonance imaging (fMRI) techniques and selective pharmacological tools, it aims to explore the neuropharmacology of putative relapse pathways in cocaine, alcohol, opiate dependent, and healthy individuals to inform future drug development. Addiction studies typically involve small samples because of recruitment difficulties and attrition. We established the platform in three centres to assess the feasibility of a multisite approach to address these issues. Pharmacological modulation of reward, impulsivity and emotional reactivity were investigated in a monetary incentive delay task, an inhibitory control task, and an evocative images task, using selective antagonists for µ-opioid, dopamine D3 receptor (DRD3) and neurokinin 1 (NK1) receptors (naltrexone, GSK598809, vofopitant/aprepitant), in a placebo-controlled, randomised, crossover design. In two years, 609 scans were performed, with 155 individuals scanned at baseline. Attrition was low and the majority of individuals were sufficiently motivated to complete all five sessions ( n=87). We describe herein the study design, main aims, recruitment numbers, sample characteristics, and explain the test hypotheses and anticipated study outputs.

Mechanical properties of skinned single fibres from rabbit psoas muscle have been correlated with biochemical steps in the cross‐bridge cycle using a series of metal–nucleotide (Me·NTP) substrates (Mn2+ or Ni2+ substituted for Mg2+; CTP or ITP for ATP) and inorganic phosphate. Measurements were made of the rate of force redevelopment following (1) slack tests in which force recovery followed a period of unloaded shortening, or (2) ramp shortening at low load terminated by a rapid restretch. The form and rate of force recovery were described as the sum of two exponential functions. Actomyosin‐Subfragment 1 (acto‐S1) Me·NTPase activity and Me·NDP release were monitored under the same conditions as the fibre experiments. Mn·ATP and Mg·CTP both supported contraction well and maintained good striation order. Relative to Mg·ATP, they increased the rates and Me·NTPase activity of cross‐linked acto‐S1 and the fast component of a double‐exponential fit to force recovery by ∼50% and 10–35%, respectively, while shortening velocity was moderately reduced (by 20–30%). Phosphate also increased the rate of the fast component of force recovery. In contrast to Mn2+ and CTP, Ni·ATP and Mg·ITP did not support contraction well and caused striations to become disordered. The rates of force recovery and Me·NTPase activity were less than for Mg·ATP (by 40–80% and 50–85%, respectively), while shortening velocity was greatly reduced (by ∼80%). Dissociation of ADP from acto‐S1 was little affected by Ni2+, suggesting that Ni·ADP dissociation does not account for the large reduction in shortening velocity. The different effects of Ni2+ and Mn2+ were also observed during brief activations elicited by photolytic release of ATP. These results confirm that at least one rate‐limiting step is shared by acto‐S1 ATPase activity and force development. Our results are consistent with a dual rate‐limitation model in which the rate of force recovery is limited by both NTP cleavage and phosphate release, with their relative contributions and apparent rate constants influenced by an intervening rapid force‐generating transition.