Histological investigation of amygdala in horned and hornless ewes

The amygdala is the nucleus of the brain that is largely responsible for perceiving danger and plays a role in emotion, behavior, control and learning. A small amygdala has been associated to aggression. Horned ewes are expected to be more aggressive and have a smaller amygdala. Both horned and hornless ewes exhibit intraspecific head-butting behavior and both species are at risk for traumatic brain injury. The aim of this study was to investigate the neuronal density, glial cells and blood-brain barrier (BBB) of the amygdala in horned and hornless ewes. Four horned and six hornless ewe heads (age: 16.00 ± 4.00 months) were obtained from the abattoir. The brains were carefully removed and preserved in 10.00% formalin for 5 days. Bilateral amygdalae were sectioned. The samples were stained with Hematoxylin and Eosin, immunohistochemical (glial fibrillary acidic protein) and Terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling methods, and the histological structures of the amygdala were examined by light microscopy. The Mann-Whitney U test was used to analyze the data. Neuronal density was estimated to be 143,230 ± 12,540 per mm³ in horned and 152,230 ± 18,430 per mm³ in hornless ewes. Horned subjects had reduced numbers of neurons, damaged BBB and localized inflammatory areas. More apoptotic neurons were observed in horned ewes. Further studies are needed to determine whether these differences in neuronal density, glial cells, and BBB are acquired (due to trauma) or congenital. The results of this study might need further similar studies to be conducted in the future.