Simultaneously changes in striatum dopaminergic and glutamatergic parameters following hypoxic-ischemic neuronal injury in newborn piglets

Role of 5HT1A Receptors in the Neuroprotective and Behavioral Effects of Cannabidiol in Hypoxic–Ischemic Newborn Piglets

Background: Hypoxic–ischemic (HI) insults have important deleterious consequences in newborns, including short-term morbidity with neuromotor and cognitive disturbances. Cannabidiol (CBD) has demonstrated robust neuroprotective effects and shows anxiolytic/antidepressant effects as well. These effects are thought to be related to serotonin 5-HT_1A receptor (5HT_1AR) activation. We hereby aimed to study the role of 5HT_1AR in the neuroprotective and behavioral effects of CBD in HI newborn piglets.

Methods: 1-day-old piglets submitted to 30 min of hypoxia (FiO2 10%) and bilateral carotid occlusion were then treated daily with vehicle, CBD 1 mg/kg, or CBD with the 5HT_1AR antagonist WAY 100635 1 mg/kg 72 h post-HI piglets were studied using amplitude-integrated EEG to detect seizures and a neurobehavioral test to detect neuromotor impairments. In addition, behavioral performance including social interaction, playful activity, hyperlocomotion, and motionless periods was assessed. Then, brain damage was assessed using histology (Nissl and TUNEL staining) and biochemistry (proton magnetic resonance spectroscopy studies.

Results: HI led to brain damage as assessed by histologic and biochemistry studies, associated with neuromotor impairment and increased seizures. These effects were not observed in HI piglets treated with CBD. These beneficial effects of CBD were not reversed by the 5HT_1AR antagonist, which is in contrast with previous studies demonstrating that 5HT_1AR antagonists eliminated CBD neuroprotection as assessed 6 h after HI in piglets. HI led to mood disturbances, with decreased social interaction and playfulness and increased hyperlocomotion. Mood disturbances were not observed in piglets treated with CBD, but in this case, coadministration of the 5HT_1AR antagonist eliminates the beneficial effects of CBD.

Conclusion: CBD prevented HI-induced mood disturbances in newborn piglets by acting on 5HT_1AR. However, 5HT_1AR activation seems to be necessary for CBD neuroprotection only in the first hours after HI.

Expression Changes in Lactate and Glucose Metabolism and Associated Transporters in Basal Ganglia following Hypoxic-Ischemic Reperfusion Injury in Piglets

BACKGROUND AND PURPOSE

The neonatal brain has active energy metabolism, and glucose oxidation is the major energy source of brain tissue. Lactate is produced by astrocytes and released to neurons. In the central nervous system, lactate is transported between neurons and astrocytes via the astrocyte-neuron lactate shuttle. The aim of this study was to investigate the regulatory mechanisms of energy metabolism in neurons and astrocytes in the basal ganglia of a neonatal hypoxic-ischemic brain injury piglet model.

MATERIALS AND METHODS

A total of 35 healthy piglets (3-5 days of age; 1.0-1.5 kg) were assigned to a control group (n = 5) or a hypoxic-ischemic model group (n = 30). The hypoxic-ischemic model group was further divided into 6 groups according to the ¹H-MR spectroscopy and PET/CT scan times after hypoxia-ischemia (0-2, 2-6, 6-12, 12-24, 24-48, and 48-72 hours; n = 5/group). ¹H-MR spectroscopy data were processed with LCModel software. Maximum standard uptake values refer to the maximum standard uptake values for glucose (or FDG). The maximum standard uptake values of the basal ganglia-to-occipital cortex ratio were analyzed. The expression levels of glucose transporters and monocarboxylate transporters were detected by immunohistochemical analysis.

RESULTS

Lactate levels decreased after an initial increase, with the maximal level occurring around 2-6 hours following hypoxia-ischemia. After hypoxia-ischemia, the maximum standard uptake values of the basal ganglia and basal ganglia/occipital cortex initially increased then decreased, with the maximum occurring at approximately 6-12 hours. The lactate and glucose uptake (basal ganglia/occipital cortex maximum standard uptake values) levels were positively correlated. The expression levels of glucose transporter-1 and glucose transporter-3 were positively correlated with the basal ganglia/occipital cortex. The expression levels of monocarboxylic acid transporter-2 and monocarboxylic acid transporter-4 were positively correlated with lactate content.

CONCLUSIONS

The results indicate that lactate and glucose transporters have a synergistic effect on the energy metabolism of neurons and astrocytes following hypoxic-ischemic reperfusion brain injury.

Early Changes in Glutamate Metabolism and Perfusion in Basal Ganglia following Hypoxia-Ischemia in Neonatal Piglets: A Multi-Sequence 3.0T MR Study

The excitotoxicity of glutamate metabolism as well as hemodynamic disorders of the brain are both risk factors for neonatal hypoxic–ischemic brain damage (HIBD). In the present study, changes in glutamate metabolism in the basal ganglia were detected by proton magnetic resonance spectroscopy (¹H-MRS) at 0–6, 8–12, 24–30, and 48–60 h after the induction of hypoxia-ischemia (HI) in newborn piglets. Meanwhile, correlation analysis was performed by combining the microcirculatory perfusion informations acquired by intravoxel incoherent motion (IVIM) scan to explore their possible interaction mechanism. The results suggested that Glu level in the basal ganglia underwent a “two-phase” change after HI; perfusion fraction f, an IVIM-derived perfusion parameter, was clearly decreased in the early stage after HI, then demonstrated a transient and slight recovery process, and thereafter continued to decrease. The changes in f and Glu level were in a significant negative correlation (r = −0.643, P = 0.001). Our study results revealed that Glu level is closely associated with the microcirculatory perfusion changes in the acute stage of HIBD.

Measurement of Lactate Content and Amide Proton Transfer Values in the Basal Ganglia of a Neonatal Piglet Hypoxic-Ischemic Brain Injury Model Using MRI

BACKGROUND AND PURPOSE

As amide proton transfer imaging is sensitive to protein content and intracellular pH, it has been widely used in the nervous system, including brain tumors and stroke. This work aimed to measure the lactate content and amide proton transfer values in the basal ganglia of a neonatal piglet hypoxic-ischemic brain injury model by using MR spectroscopy and amide proton transfer imaging.

MATERIALS AND METHODS

From 58 healthy neonatal piglets (3-5 days after birth; weight, 1-1.5 kg) selected initially, 9 piglets remained in the control group and 43 piglets, in the hypoxic-ischemic brain injury group. Single-section amide proton transfer imaging was performed at the coronal level of the basal ganglia. Amide proton transfer values of the bilateral basal ganglia were measured in all piglets. The ROI of MR spectroscopy imaging was the right basal ganglia, and the postprocessing was completed with LCModel software.

RESULTS

After hypoxic-ischemic insult, the amide proton transfer values immediately decreased, and at 0-2 hours, they remained at their lowest level. Thereafter, they gradually increased and finally exceeded those of the control group at 48-72 hours. After hypoxic-ischemic insult, the lactate content increased immediately, was maximal at 2-6 hours, and then gradually decreased to the level of the control group. The amide proton transfer values were negatively correlated with lactate content (r = -0.79, P < .05).

CONCLUSIONS

This observation suggests that after hypoxic-ischemic insult, the recovery of pH was faster than that of lactate homeostasis.

Angiogenic, neurotrophic, and inflammatory system SNPs moderate the association between birth weight and ADHD symptom severity

Low birth weight is associated with increased risk for Attention-Deficit/Hyperactivity Disorder (ADHD); however, the etiological underpinnings of this relationship remain unclear. This study investigated if genetic variants in angiogenic, dopaminergic, neurotrophic, kynurenine, and cytokine-related biological pathways moderate the relationship between birth weight and ADHD symptom severity. A total of 398 youth from two multi-site, family-based studies of ADHD were included in the analysis. The sample consisted of 360 ADHD probands, 21 affected siblings, and 17 unaffected siblings. A set of 164 SNPs from 31 candidate genes, representing five biological pathways, were included in our analyses. Birth weight and gestational age data were collected from a state birth registry, medical records, and parent report. Generalized Estimating Equations tested for main effects and interactions between individual SNPs and birth weight centile in predicting ADHD symptom severity. SNPs within neurotrophic (NTRK3) and cytokine genes (CNTFR) were associated with ADHD inattentive symptom severity. There was no main effect of birth weight centile on ADHD symptom severity. SNPs within angiogenic (NRP1 & NRP2), neurotrophic (NTRK1 & NTRK3), cytokine (IL16 & S100B), and kynurenine (CCBL1 & CCBL2) genes moderate the association between birth weight centile and ADHD symptom severity. The SNP main effects and SNP × birth weight centile interactions remained significant after adjusting for multiple testing. Genetic variability in angiogenic, neurotrophic, and inflammatory systems may moderate the association between restricted prenatal growth, a proxy for an adverse prenatal environment, and risk to develop ADHD.