Large animal models are an essential tool in the development of rationally-based new clinical therapies for preterm infants. We provide a description of the newborn pig as a model of the preterm neonate in terms of growth parameters, physiology and the requirement for intensive care over a range of gestational ages. Twenty-nine litters of piglets (n = 298) were delivered by caesarean section at six timepoints during gestation from 91d to 113d (term = 115d). Two groups, at 91 and 97d gestation, also received maternal glucocorticoid treatment. At four of these timepoints, piglets (n = 79) were ventilated, sedated and monitored using standard neonatal intensive care techniques for up to 8 h in various experimental protocols. Body weight increased from mean 697 g (SD 193) at 91d gestation to 1331 g (SD 368) at 113d gestation. Piglets delivered at 97d gestation were able to be resuscitated and kept alive for at least 8 h on respiratory support after surfactant administration. Maternal glucocorticoid treatment 48 h and 24 h hours prior to delivery reduced the requirement for ventilator support and improved cardiovascular stability. The pig provides a relevant model for the study of human preterm physiology and for investigation of novel therapies to improve outcomes.

The use of lower formalin-containing embalming solution for anatomy cadaver preparation

Highlights:   Abstract: Spatial working memory (SWM) in humans and animal models with impaired cognitive functions has been analyzed through a number of methods. However, this is still understudied in animal models treated with a high-calorie diet (HCD) and moderate-intensity exercise (MIE). The Y-maze was utilized as the assessment method in this study. A 40 x 9 x 9 cm3 Y-maze was employed to observe the animal models’ spontaneous alternation (SA) as the representation of their SWM. This was done by calculating the total alternation percentage divided by total entry minus two. A total of 17 female Mus musculus mice aged 8 weeks were tested in the Y-maze to investigate their SWM using SA calculations. Each mouse was analyzed for eight minutes and recorded in a dark and quiet room to minimize bias due to environmental noise and lighting. Comparing the treatment group’s (HCD+MIE) SA to the control group’s SA revealed no statistically significant difference (p=0.451). Seven mice in the treatment group performed similarly to the mice in the control group in the Y-maze test, with no significant difference in their ability to complete the task. The mice in the treatment group exhibited no motor impairment, as indicated by complete movements of all their extremities while exploring the Y-maze within the allotted time. In conclusion, the Y-maze can be used as a reliable method to analyze SWM in overweight/obese Mus musculus animal models treated with moderate-intensity physical exercise.

GABA is a major neurotransmitter in the mammalian brain. In the mature brain GABA exerts inhibitory actions via the GABAA receptor (GABAAR); however, in the immature brain GABA provides much of the excitatory drive. We examined the expression of 3 predominant GABAA α-subunit proteins in the pig brain at various pre- and postnatal ages. Brain tissue was collected from piglets born via caesarean section at preterm ages 91, 97, 100, and 104 days' gestational age (GA), at term equivalent (114 days' GA, caesarean section) and at term, postnatal day 0 (P0) (spontaneous delivery, term = 115 days). Tissue was obtained from piglets at P4 and P7. Adult tissue from sows was collected postmortem after caesarean section. In all cortical regions and basal ganglia (1) α3 exhibited a significant increase in protein expression at 100 days' GA, (2) α3 expression decreased with age after 100 days' GA, (3) α1 increased with age, with peak expression at P7 in cortices, hippocampus, and thalamus, and (4) α2 protein expression remained relatively constant across the ages examined. The subunit expression of α3 was most abundant at preterm ages, with α1 the predominant subunit expressed postnatally. Immunofluorescent labelling revealed α1 expression on the somatic membranes of pyramidal cells in the cortex and hippocampus, and in the cerebellar Purkinje cells. Positive α3 labelling was apparent on interneurones in the cortex and hippocampus. The switch between dominant α-subunits may coincide with the functional change in GABAergic neurotransmission from excitation to inhibition. Brain growth in the pig closely reflects that in the term human, making the pig a valuable non-primate model for studying development and the effects of insults on the perinatal brain.

The principal function of the γ-aminobutyric acid (GABA) system in the adult brain is inhibition; however, in the neonatal brain, GABA provides much of the excitatory drive. As the brain develops, transmembrane chloride gradients change and the inhibitory role of GABA is initiated and continues throughout juvenile and adult life. Previous studies have shown that GABAA receptor subunit expression is developmentally regulated, and it is thought that the change in GABA function from excitation to inhibition corresponds to the changeover in expression of ‘immature’ to ‘mature’ subunit isoforms. We examined the protein expression pattern and distribution of GABA type A (GABAA) receptor α1-, α3- and β2-subunits in the parietal cortex and hippocampus of the developing piglet brain. Four perinatal ages were studied; 14 days preterm (P–14), 10 days preterm (P–10), day of birth (P0) and at postnatal day 7 (P7). Animals were obtained by either caesarean section or spontaneous birth. Protein expression levels and subunit localization were analysed by Western blotting and immunohistochemistry, respectively. In the cortex and hippocampus, GABAA receptor α1-subunit showed greatest expression at P7 when compared to all other age groups (p < 0.05). In contrast, α3 expression in the cortex was elevated in preterm brain, peaking at P0, followed by a significant reduction by P7 (p < 0.05); a similar trend was observed in the hippocampus. GABAA receptor β2-subunit protein expression appeared relatively constant across all time points studied in both the cortex and hippocampus. Immunolabelling of the α1-, α3- and β2-subunits was observed throughout all cortical layers at every age. GABAA receptor α3-subunit appeared to show specific localization to layers V and VI whilst labelling for the β2-subunit was observed in layer IV. In the hippocampus of all animals, the α1- and β2-subunits were shown to immunolabel various cells and processes in the dentate gyrus (DG), CA1 and CA3; the α3-subunit was barely observed except at the stratum moleculare of the DG. We report for the first time the ontogenesis of GABAA receptor subunits α1, α3 and β2 in the perinatal pig brain.