Increased mRNA grelin receptor expression in rat cubs brain structures in models of separation from mother and social isolation

BACKGROUND: Stress exposure at an early age can have serious long-term consequences for the development of the human body, leading to adaptive disorders, increased anxiety, depression and other mental disorders in people. The effect of stressors in the first weeks after birth affects the proliferation, differentiation and migration of neurons, in particular, the neurogenesis of hippocampal cells. Repetitive stress can lead to changes in the structure and function of the brain, including deterioration of memory and skill acquisition, reduced resistance to stress in the future, decreased immune system function and increased risk of depression and other mental illnesses.

AIM: The aim was to study the effect of social isolation weaning on the level of ghrelin receptor mRNA expression in the brain structures of Wistar rats.

MATERIALS AND METHODS: 60 male rats (8 litters) with a body weight of 230–250 g were used in the work and three experimental groups were formed: control (n = 20); “maternal deprivation” (n = 20); “social isolation” (n = 20). On the 90^th day of life, the animals were decapitated, the brain was quickly extracted, placed in the cold and brain structures (hypothalamus, amygdala, prefrontal cortex) were isolated, immediately frozen in liquid nitrogen and stored at a temperature of –80°C until PCR analysis was performed. The data obtained were normalized to the expression level of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene and calculated in relative units with respect to the expression value of the GRLN-R gene for each structure separately by method 2 (-DeltaDelta C(T)).

RESULTS: In rats raised in conditions of social isolation, compared with the indicators of the control group and the group of animals with maternal deprivation (p < 0.05), an increase in the expression of the GHSR1A gene was noted in the hypothalamus. Whereas in rats after the stress of maternal deprivation in the amygdala there was an increase in the expression of the GHSR1A gene compared with the indicators in the control group of rats.

CONCLUSIONS: 1. In rats that survived weaning from the mother from the 2^nd to the 12^th postnatal day, a significant statistically significant increase in the expression of the GHSR1A gene was revealed in the hypothalamus in comparison with the control group and the social isolation group. 2. In rats raised in conditions of social isolation from their relatives, a significant statistically significant increase in the expression of the GHSR1A gene in the amygdala was revealed in comparison with the control group and the weaning group.