Effects Of Neonatal Isolation Research Articles

Effect of neonatal isolation on responses to subsequent exposure to isolation stress in young chickens

The aim of the present study was to investigate effects of isolation at an early age on behavioral and physiological responses of chickens to an isolation challenge at two weeks of age. Birds were assigned to a control group or to one of three treatments where chicks were isolated for 5 min per day. The groups were 1) no isolation (control); 2) early isolation (EI; 2 to 4 days of age); 3) late isolation (LI; 5 to 7 days of age); or 4) full isolation (FI; 2 to 7 days of age). All groups of chicks were challenged with isolation for 5 min at two weeks of age, with distress vocalizations (DV), stepping and jumping behavior measured. Hypothalamic and blood samples were collected at the end of isolation challenges. There were no significant differences between groups in body weight gain at 2 weeks of age. Latency of jump was lower in the LI group compared with the control group, but DV and number of steps were not affected by isolation treatment during the neonatal period. There were no significant differences among groups in plasma glucose or FFA concentrations. Gene expression for hypothalamic corticotropin-releasing hormone, was lower in the EI than the control group, with no differences in expression between control and LI or control and FI groups. There were no significant differences among groups in the expression of arginine vasotocin, thyrotropin-releasing hormone, neuropeptide Y, proopiomelanocortin, and orexin genes. These results suggest that isolation in the first week of life may affect responses to isolation of chicks when they are older, and that there may be a critical period of several days for this effect to occur.

Neonatal Isolation Stress Inhibits Pre-Weaning Weight Gain and Mild-Stressor Induced Locomotor Activity in Early Adolescent Male and Female Rats

The present study looked at the effects of neonatal isolation, an early life stress experience, in male and female early adolescent rats, an age which is underrepresented in the early stress literature. Four stress-sensitive indices were assessed: weight gain during the pre-weaning period, open field activity, and locomotor activity in response to two mild stressors: exposure to a novel environment, and a single IP saline injection. Rats in the neonatal isolation condition were removed from dam and littermates on postnatal days 2-9 in accord with the procedure used by Kehoe et al. (1995); behavioral testing occurred on PN25-PN30 during the early adolescent period. It was found that neonatally isolated pups weighed less than non-isolate controls on each of three measurement days (PN7, PN14, PN21) throughout the pre-weaning period. Further, neonatal isolation experience consistently reduced horizontal locomotor activity measured in the open field, in a novel environment, and following a single mild acute stressor. On some measures, behavior reflected greater impact of NI in males compared with NI females, suggesting that the effects of NI in early adolescent rats may be sexually dimorphic.

The effects of neonatal cryoanaesthesia-induced hypothermia on adult emotional behaviour and stress markers in C57BL/6 mice

Since the early 1930s, deep hypothermia (cryoanaesthesia) has been a useful anaesthetic in several types of surgery on neonatal rodents. Especially against the background of modern techniques in systems neuroscience, the method enjoys again increasing popularity. However, little is known about its effects on the subsequent adult behavioural and physiological profile. To systematically investigate the effects of neonatal cryoanaesthesia on adult basal and emotional behaviour as well as on physiological development, 59 C57BL/6 mouse pups were randomly assigned to one of three treatment groups: Pups of the first group were exposed to the hypothermia treatment (H) on postnatal day 3, while pups of the other two groups served as controls: These pups either remained in the home cage without any intervention (C), or were separated from the mother for 15min (MS) to differentiate between effects of neonatal isolation alone versus hypothermia that inevitably goes along with neonatal isolation. Subsequent behavioural analyses were conducted during adulthood (P 84–P 130), including tests for exploratory, anxiety-like and depression-like behaviour. At the age of about 145 days mice were decapitated to record BDNF levels in the hippocampus and serum corticosterone. Altogether, H mice were found to display slightly increased anxiety levels on the O-Maze, but did not differ from the control animals in any other behavioural test. Subtle alterations in anxiety-like behaviour, however, were not accompanied by physiological changes in serum corticosterone and hippocampal BDNF levels, arguing against an overall long-lasting effect of neonatal hypothermia on the emotional profile of adult mice.

Effect of neonatal isolation on the noradrenergic transduction system in the rat hippocampal slice.

Numerous studies suggest that early adverse experiences induce neurochemical, morphological, and functional changes in the hippocampus in adolescence and adulthood. The aim of this study was to identify the influence of neonatal isolation (NI) on noradrenaline (NA)-mediated intracellular calcium ([Ca(2+)](i)) mobilization. To measure [Ca(2+)](i), we used the Ca(2+)-sensitive dye fura-2 and analysis by fluorescence microscopy. First, we examined the contributions of adrenergic receptor subtypes to the NA-stimulated increase in [Ca(2+)](i) in the granule cell layers of the dentate gyrus (DG) and in the pyramidal cell layers of the CA3 in the hippocampus. Second, we found that the NA-stimulated [Ca(2+)](i) increment was significantly decreased in response to NI in these hippocampal regions. In addition, we examined the influence of environmental enrichment (EE) after weaning on the decrease in the NA-stimulated [Ca(2+)](i) increment induced by NI. The administration of EE reversed the influence of NI on the NA-stimulated [Ca(2+)](i) increment in the CA3 pyramidal cell layer but not in the DG granular cell layer in the hippocampus. These findings suggest that NI and EE after weaning may modulate hippocampal function by altering adrenergic receptor-mediated signal transduction during adolescence.