Impact of locomotion restraint during the neonatal period on some hormonal and behavoural aspects in male rats

ABSTRACT

The early stage of neonatal life is considered a crucial period for the development and differentiation of the nervous system and any impairment in the neuro-developmental aspects may result in a life-long modification. Accordingly, this study was designed to investigate the impact of restraint from the 21st day to the 42nd day in rat's neonatal period on some biochemical, behavioural and emotionality _related aspects. At the age of three weeks, young rats were exposed to 21 days of locomotion restraint for 6 h/day after which, the rats of both the control unstressed group and those that were exposed to the stressful regimen were subjected to the behavioural assessments using the exploratory and aggressive behaviour tests. After completion of these tests, the rats were sacrificed to determine the tissue brain cortex acetylcholinesterase [AChE] activity and total protein content. Serum levels of glucose, total cholesterol, testosterone, luteinizing hormone [LH], prolactin [PRL], thyroid stimulating hormone [TSH], thyroxine [T4], triiodothyronine [T3] in addition to the plasma levels of adrenocorticotropin [ACTH] were estimated. The present findings revealed that rats exposed to restraint stress exhibited significant shortcomings in the exploratory test with high rates of emotionality and excitability as revealed by their aggressiveness. These behavioural deviations were concomitant with disturbances in the endocrine balance as indicated by a decline in the levels of serum T3, PRL, testosterone, LH and a rise in plasma ACTH as well as serum glucose and cholesterol levels. The present study explicitly indicates that exposure to stress during the early stage of life results in long-lasting behavioural and neuro-endocrine alterations in the adult rats