| The process of birth (parturition) has a critical impact on normal human development. Any deviations from the typical parturition process are defined clinically as birth complications, and have been linked to the development of neurological deficits. Two relatively common types of consequences from birth complications are perinatal asphyxia and Caesarean Section delivery (C-section); however, C-section is becoming more common as a matter of choice (elective C-section delivery) rather than as a consequence of some birth complication (Barber et al., 2011; Martin et al., 2012). The two consequences of birth complications differ: perinatal asphyxia involves extended periods of oxygen deprivation during delivery, whereas elective C-section deprives the fetus of the typical conditions associated with a vaginal delivery. Animal research reveals that both perinatal asphyxia and C-section lead to increased expression of dopamine in the mesolimbic dopaminergic pathway. Since this dopaminergic pathway is important for learning, attention, working memory, motivation, movement and mood there is evidence that such increases in dopamine expression result in deficits in these functions. Because the mesolimbic dopaminergic system innervates the hypothalamus, previous research suggested that the complication of perinatal asphyxia results in an increased sensitivity to stress via alterations in the functioning of the hypothalamic-pituitary-adrenal (HPA) axis. Such alterations may be apparent in the development of sensitivity to stressful situations. One test of sensitivity to stressful situations for rodents is to present a resident adult male with an adult male intruder. This social situation can be marked by investigatory and aggressive behaviors on the part of the resident male. The hypothesis for this thesis is that perinatal asphyxia and C-section delivery of male rats will result in differences in adult investigatory and aggressive social behaviors in this stress test. This study compares the social behavior of 55 day old, postpubertal male rats exposed to asphyxia and C-section at birth, with that of vaginally delivered rats. The social behaviors also were examined in relation to neuroanatomical and neurochemical alterations in dopamine transmission, specifically in the nucleus accumbens. |
