International Journal of Developmental Neuroscience

The present study was conducted to investigate the effect of experimentally‐induced hyperthyroidism on dopamine (DA), norepinephrine (NE) and serotonin (5‐HT) levels in different brain regions as well as in blood plasma, cardiac muscle and adrenal gland of young and adult male albino rats (60 rats of each age). Hyperthyroidism was induced by daily s.c. injection of L‐thyroxine (L‐T₄, 500 μg/kg body wt.) for 21 consecutive days. Induction of hyperthyroidism caused a significant elevation in DA and 5‐HT levels in most of the tissues studied of both young and adult animals after 7, 14, and 21 days. NE content significantly decreased after 21 days in most of the brain regions examined and after 14 and 21 days in blood plasma of young rats following hyperthyroidism. In adult rats, NE content decreased after 14 and 21 days in cardiac muscle and after 21 days only in adrenal gland. It may be suggested that the changes in monoamines level induced by hyperthyroidism may be due to disturbance in the synthesis, turnover and release of these amines through the neurons impairment or may attributed to an alteration pattern of their synthesis and/or degradative enzymes or changes in the sensitivity of their receptors

It is usually difficult to distinguish small pineal tumors via routine or enhanced magnetic resonance (MR) scan. The knowledge of normal pineal size is helpful to detect small pineal lesions, while very few true volumetric data of pineal glands have been reported. Therefore, we obtained the accurate reference range of normal pineal volumes in 112 individuals aged 20–30 years recruited randomly from a healthy community sample. Transverse and sagittal 3.0 T magnetic resonance data were obtained using three‐dimensional (3D) T1‐weighted FSPGR and T2‐weighted SE sequences. True pineal volumes were measured from T1‐weighted images, while estimated volumes were calculated using pineal length, width and height. All the glands were divided into three types according to the maximum inner diameter of pineal cysts. The prevalence of asymptomatic pineal cyst is 25.00%, with a slight female predominance. In the whole sample, we found no gender differences of pineal volume, but a significant gender difference of pineal volume index. A significant correlation between pineal volume and asymptomatic cyst was found. After excluding cases with big pineal cysts, there were significant correlations between pineal volume and head circumference, body height and body weight, respectively. This study suggests that asymptomatic pineal cysts may exert an important influence on pineal volume.

Studies of human neonates, and in animal experiments, suggest that birth asphyxia results in functional compromise of the hippocampus, even when structural damage is not observable or resolves in early postnatal life. The aim of this study was to determine if changes in hippocampal function occur in a model of birth asphyxia in the precocial spiny mouse where it is reported there is no major lesion or infarct. Further, to assess if, as in human infants, this functional deficit has a sex‐dependent component. At 37 days gestation (term = 39 days) spiny mice fetuses were either delivered immediately by caesarean section (control group) or exposed to 7.5 min of in utero asphyxia causing systemic acidosis and hypoxia. At 5 days of age hippocampal function was assessed ex vivo in brain slices, or brains were collected for examination of structure or protein expression. This model of birth asphyxia did not cause infarct or cystic lesion in the postnatal day 5 (P5) hippocampus, and the number of proliferating or pyknotic cells in the hippocampus was unchanged, although neuronal density in the CA1 and CA3 was increased. Protein expression of synaptophysin, brain‐derived neurotrophic factor (BDNF), and the inositol trisphosphate receptor 1 (IP₃R1) were all significantly increased after birth asphyxia, while long‐term potentiation (LTP), paired pulse facilitation (PPF), and post‐tetanic potentiation (PTP) were all reduced at P5 by birth asphyxia. In control P5 pups, PPF and synaptic fatigue were greater in female compared to male pups, and after birth asphyxia PPF and synaptic fatigue were reduced to a greater extent in female vs. male pups. In contrast, the asphyxia‐induced increase in synaptophysin expression and neuronal density were greater in male pups. Thus, birth asphyxia in this precocial species causes functional deficits without major structural damage, and there is a sex‐dependent effect on the hippocampus. This may be a clinically relevant model for assessing treatments delivered either before or after birth to protect this vulnerable region of the developing brain.

Perinatal hypoxia commonly causes brain injury in infants, but the time course and mechanisms underlying the preferential male injury are unclear. Intermittent hypoxia disturbs cerebellar γ‐aminobutyric (GABA)‐A receptor profiles during the perinatal period, possibly responding to transient excitatory processes associated with GABA_A receptors. We examined whether hypoxic insults were particularly damaging to the male rodent cerebellum during a specific developmental time window. We evaluated cerebellar injury and GABA_A receptor profiles following 5‐h intermittent hypoxia (IH: 20.8% and 10.3% ambient oxygen, switched every 240 s) or room‐air control in groups of male and female rat pups on postnatal d 1–2, wk 1, or wk 3. The cerebella were harvested and compared between groups. The mRNA levels of GABA_A receptors α6, normalized to a house‐keeping gene GAPDH, and assessed using real‐time reverse‐transcriptase PCR assays were up‐regulated by IH at wk 1, more extensively in male rats, with sex influencing the regulatory time‐course. In contrast, GABA_A α6 receptor protein expression levels, assessed using Western blot assays, reached a nadir at wk 1 in both male and female rats, possibly indicating involvement of a post‐transcriptional mechanism. The extent of cerebellar damage and level of apoptosis, assessed by DNA fragmentation, were greatest in the wk 3 IH‐exposed group. The findings suggest partial protection for female rats against early hypoxic insult in the cerebellum, and that down‐regulation of GABA_A receptors, rather than direct neural injury assessed by DNA fragmentation may modify cerebellar function, with potential later motor and other deficits.

When it occurs early in life, Status epilepticus (SE) can cause behavioural and cognitive impairments in adulthood. Here, we evaluated the putative benefits of low‐intensity treadmill training on long‐standing cognitive impairment in rats submitted to SE early in life. Wistar rats were submitted to LiCl‐pilocarpine‐induced SE at P16. Animals from the trained group underwent a low‐intensity treadmill protocol for 5 days per week for 4 weeks. At adulthood, rats subjected to early‐life SE displayed impairment in long‐term memory in an object recognition task, while the training protocol completely reversed this deficit. This result was associated with neither locomotor alterations nor changes in emotional behaviour; there were no differences between groups in the distance travelled, grooming or rearing in the open field test; there were also no differences between groups in the number of risk assessment, time spent in open arms in an elevated plus maze and number of entries into the open arms. These data suggest that physical exercise can ameliorate the long‐standing recognition memory deficit induced by early‐life SE, suggesting that it may be useful as a putative intervention for patients who suffered SE during infancy.