Effects of Maternal Deprivation on the Prefrontal Cortex of Male Rats: Cellular, Neurochemical, and Behavioral Outcomes

Stressful events experienced during early life are associated with increased vulnerability of developing psychopathology in adulthood. In the present study, we exposed 9-day-old Wistar rats to 24 h maternal deprivation (MD) with the aim to investigate the impact of early life stress (ELS) on morphological, biochemical, and functional aspects of the prefrontal cortex (PFC), a brain region particularly sensitive to stress. We found that in the superficial medial orbital cortex (MO), young adult male rats had reduced density of GAD67 and CCK immunopositive cells, while the rostral part of the ventral lateral orbital cortex (roVLO) showed a decrease in the density of GAD67 immunopositive cells in both superficial and deep layers. In addition, the superficial rostral part of area 1 of the cingulate cortex (roCg1) and deep prelimbic cortex (PrL) was also affected by MD indicated by the reduction in PV immunopositive cellular density. Furthermore, MD induced upregulation of brain-derived neurotrophic factor (BDNF), while it did not affect the overall expression of Iba1 in neonatal or young adult PFC as measured by Western blot, however, microglial activation in young adult MD rats was detected immunohistochemically in deep layers of MO and infralimbic cortex (IL). Interestingly, when young adult male rats were subjected to a behavioral flexibility test in a T-maze, MD rats showed a subtle impairment in T-maze reversal learning indicating a mildly affected PFC function. Taken together, our findings demonstrated that MD reduced the density of interneurons and induced microglial activation, in particular, PFC areas at young adulthood, and could alter synaptic plasticity accompanied by PFC dysfunction.

Morphological and Histological Features of the Vomeronasal Organ in African Pygmy Hedgehog (Atelerix albiventris)

The vomeronasal organ (VNO) detects specific chemicals such as pheromones and kairomones. Hedgehogs (Eulipotyphla: Erinaceidae) have a well-developed accessory olfactory bulb that receives projections from the VNO, but little is known about the hedgehog VNO. Here, we studied the histological features of the VNO in five individual African pygmy hedgehogs by hematoxylin-eosin, periodic acid-Schiff, and Alcian blue stains. The hedgehog VNO comprises a hyaline cartilage capsule, soft tissue and epithelial lumen, and it branches from the site just before the incisive duct opening into the nasal cavity. The soft tissues contain several small mucous (or mucoserous) glands and a large serous gland, and many venous sinuses all around the lumen. The VNO lumen is round to oval throughout the hedgehog VNO, and the sensory epithelium lines almost the entire rostral part and medial wall of the middle part. These findings indicate that the VNO is functional and plays an important role in the hedgehog. Notably, the VNO apparently has a characteristic flushing mechanism with serous secretions like those of gustatory glands, which the hedgehog might frequently use to recognize the external environment.

Bit-Related Lesions in Event Horses After a Cross-Country Test

Bit-related oral lesions are common and may impair horse welfare. The aim of this study was to investigate the prevalence of oral lesions and their risk factors in a sample of Finnish event horses. The rostral part of the oral cavity (the bit area) of 208 event horses (127 warmbloods, 52 coldbloods, and 29 ponies) was examined in a voluntary inspection after the last competition phase, i.e., the cross-country test. Acute lesions were observed in 52% (109/208) of the horses. The lesion status was graded as no acute lesions for 48% (99/208), mild for 22% (45/208), moderate for 26% (55/208) and severe for 4% (9/208) of the horses. The inner lip commissure was the most common lesion location observed in 39% (81/208) of the horses. A multivariable logistic regression model with data of 174 horses was applied to risk factor analysis. Horses wearing thin (10–13 mm) (OR 3.5, CI 1.4–8.7) or thick (18–22 mm) (OR 3.4, CI 1.4–8.0) bits had a higher risk of moderate/severe lesion status than horses wearing middle-sized (14–17 mm) bits (P = 0.003). Breed was associated with moderate/severe lesion status (P = 0.02). The risk was higher for warmbloods (reference group) and coldbloods (OR 2.0, CI 0.88–4.7) compared with ponies (OR 0.2, CI 0.04–0.87). Mares were at higher risk of moderate/severe lesion status (OR 2.2, CI 1.1–4.5) than geldings (reference group) (P = 0.03). Bar lesions were more common in horses with unjointed bits (40%, 8/20) than with basic double-jointed (10%, 5/52), formed double-jointed (8%, 6/78) or single-jointed bits (5%, 2/40) (Fisher's exact test, P = 0.002). The results of this study suggest that thin and thick bits and mare sex should be considered risk factors for mouth lesions. In addition, in this sample ponies had smaller risk for lesions than other horse breeds. We encourage adopting bit area monitoring as a new routine by horse handlers and as a welfare measure by competition organizers for randomly drawn horses.

Preferential Neuronal Responses to Snakes in the Monkey Medial Prefrontal Cortex Support an Evolutionary Origin for Ophidiophobia

Ophidiophobia (snake phobia) is one of the most common specific phobias. It has been proposed that specific phobia may have an evolutionary origin, and that attentional bias to specific items may promote the onset of phobia. Noninvasive imaging studies of patients with specific phobia reported that the medial prefrontal cortex (mPFC), especially the rostral part of the anterior cingulate cortex (rACC), and amygdala are activated during the presentation of phobogenic stimuli. We propose that the mPFC-amygdala circuit may be involved in the pathogenesis of phobia. The mPFC receives inputs from the phylogenically old subcortical visual pathway including the superior colliculus, pulvinar, and amygdala, while mPFC neurons are highly sensitive to snakes that are the first modern predator of primates, and discriminate snakes with striking postures from those with non-striking postures. Furthermore, the mPFC has been implicated in the attentional allocation and promotes amygdala-dependent aversive conditioning. These findings suggest that the rACC focuses attention on snakes, and promotes aversive conditioning to snakes, which may lead to anxiety and ophidiophobia.

Neurodevelopment

The pre- and post-natal development of the human nervous system is briefly described, with special emphasis on the brain, particularly the cerebral and cerebellar cortices. The central nervous system originates from a specialized region of the ectoderm—the neural plate—which develops into the neural tube. The rostral part of the neural tube forms the adult brain, whereas the caudal part (behind the fifth somite) differentiates into the spinal cord. The embryonic brain has three vesicular enlargements: the forebrain, the midbrain, and the hindbrain. The histogenesis of the spinal cord, hindbrain, cerebellum, and cerebral cortex, including myelination, is discussed. The chapter closes with a description of the development of the hemispheric shape and the formation of gyri.

Damage-related changes in the cerebellum of juvenile Oncorhynchus masou: reactivation of neurogenic niches and astrocytic response

ABSTRACTIn the cerebellum of juvenile Oncorhynchus masou, proliferating BrdU+ and HuCD+ cells and constitutive neurogenic niches were detected in different zones; the largest number of labeled cells were found in the dorsal part of the molecular layer and the dorsal matrix zone (DMZ). Cells labeled with glutamine synthetase (GS) and radial glia were also present in the intact O. masou cerebellum. The most intensive proliferation was detected in the rostral part of cerebellum. This part is assumed to contain active zones of constitutive neurogenesis. After an injury inflicted to the cerebellum, the number of BrdU+ and HuCD+ cells increased significantly. The number of BrdU+ cells after this type of injury was much greater than after a telencephalon trauma. A quantitative analysis revealed that after the cerebellum injury the proliferative activity in the caudal part of CCb is increased compared to that in the control. A reactivation of neurogenic and neuroepithelial niches and their transformation into reactive neurogenic domains, with an increased distribution density of intensely labeled HuCD+ cells of different types, were observed. The increase in the number of HuCD+ differentiated cells in the basal area suggests that the processes of neuronal differentiation are intensified in the cerebellum of juvenile O. masou after injury. The number of GS positive cells (GS+) and fibers increased in all the zones of cerebellum. The most intensive astrocytic response was noted in the dorsal part of cerebellum. The data of the enzyme immunoassay confirm the multiple variations in the level of GS after a traumatic injury to cerebellum in O. masou.

Revealing a Cortical Circuit Responsive to Predatory Threats and Mediating Contextual Fear Memory

The ventral part of the anteromedial thalamic nucleus (AMv) receives substantial inputs from hypothalamic sites that are highly responsive to a live predator or its odor trace and represents an important thalamic hub for conveying predatory threat information to the cerebral cortex. In the present study, we begin by examining the cortico-amygdalar-hippocampal projections of the main AMv cortical targets, namely, the caudal prelimbic, rostral anterior cingulate, and medial visual areas, as well as the rostral part of the ventral retrosplenial area, one of the main targets of the anterior cingulate area. We observed that these areas form a clear cortical network. Next, we revealed that in animals exposed to a live cat, all of the elements of this circuit presented a differential increase in Fos, supporting the idea of a predator threat-responsive cortical network. Finally, we showed that bilateral cytotoxic lesions in each element of this cortical network did not change innate fear responses but drastically reduced contextual conditioning to the predator-associated environment. Overall, the present findings suggest that predator threat has an extensive representation in the cerebral cortex and revealed a cortical network that is responsive to predatory threats and exerts a critical role in processing fear memory.

MRI of lobar holoprosencephaly in a cat with hypodipsic hypernatraemia

Case summary A 2-year-old neutered female domestic shorthair cat presented with a history of hypodipsia, recurrent hypernatraemia, pelvic limb ataxia and tremor. The serum arginine vasopressin level was low for the serum osmolality. MRI of the brain revealed a failure of separation of the cerebrum, which manifested as absence of the rostral part of the corpus callosum, fornix and septum pellucidum, thus resulting in a single fused ventricle. The diagnosis was lobar holoprosencephaly with hypodipsic hypernatraemia. Relevance and novel information To our knowledge, this is the first description of the MRI characteristics of lobar holoprosencephaly in a cat. This report suggests that MRI examination should be considered for precise diagnosis of hypodipsic hypernatraemia in young cats.