Differential effects of neonatal handling on anxiety, corticosterone response to stress, and hippocampal glucocorticoid and serotonin (5-HT)2A receptors in Lewis rats.
Neonatal handling (during the first 3 weeks of age) has been reported by others to diminish the hypothalamo-pituitary-adrenal (HPA) responsivity to stress in adult Long Evans rats, an effect involving a serotonin (5-HT)2A receptor-mediated increase in glucocorticoid receptor (GR) gene expression in the frontal cortex and the hippocampus. In addition, handled animals may also display enduring reductions in anxiety-related behaviours, including in the elevated plus-maze. We have thus analysed the aforementioned neuroendocrine and behavioural consequences of neonatal stress in male and female adult Lewis rats, a strain characterised by its high anxiety and its hyporesponsive HPA axis. Plasma corticosterone, but not behavioural, responses to an elevated plus-maze test were decreased in handled rats. Besides, hippocampal mineralocorticoid receptor (MR) and GR binding capacities were not different between handled and non-handled Lewis rats, an observation which could be extended to our adult Long Evans rats. Lastly, neither hippocampal nor cortical 5-HT2A receptor binding capacities in adult Lewis rats were affected by prior handling. In keeping with the failure to detect early handling-induced increases in hippocampal GR binding in 3-week old Lewis and Long Evans rats, the present study reinforces past findings indicating that environmental and genetic factors are crucial variables in the neonatal handling paradigm.
INSERM U471-INRA, Institut Francois Magendie, France.
M
M
Durand
A
A
Sarrieau
S
S
Aguerre
P
P
Mormède
F
F
Chaouloff
D000818:Animals; D000831:Animals, Newborn; D001143:Arousal / Q000235:genetics / Q000502:physiology*; D003345:Corticosterone / Q000097:blood*; D005260:Female; D006234:Handling, Psychological; D006624:Hippocampus / Q000502:physiology*; D007030:Hypothalamo-Hypophyseal System / Q000503:physiopathology; D008297:Male; D010913:Pituitary-Adrenal System / Q000503:physiopathology; D051381:Rats; D011917:Rats, Inbred Lew; D020318:Rats, Long-Evans; D044402:Receptor, Serotonin, 5-HT2A; D011965:Receptors, Glucocorticoid / Q000502:physiology*; D011985:Receptors, Serotonin / Q000502:physiology*; D012741:Sexual Maturation / Q000502:physiology; D012931:Social Environment; D013045:Species Specificity
D044402:Receptor, Serotonin, 5-HT2A; D011965:Receptors, Glucocorticoid; D011985:Receptors, Serotonin; D003345:Corticosterone