Emotion and Stress

Numerous studies have shown that postnatal handling (PH) of rat pups permanently alters hypothalamicpituitary-adrenal (HPA) responses to stress. As adults, handled rats exhibit reduced secretion of ACTH and corticosterone in response to stress. These effects ocur via an increase in glucocorticoid receptor density in forebrain neurons that control HPA activity which permits enhanced negative-feedback control of CRH synthesis and reduced ACTH release. Indeed, postnatally handled animals show decreased CRH levels compared with non-handled animals. The neurons located in the parvocellular region of the hypothalamic paraventricular nucleus (PVN) synthesize and release CRH. However, the consequences of early handling on other components of the central stress system are not known. The susbstantial involvement of the locus coeruleus (LC) in stress responses has been well documented in recent years. The LC, which is composed almost exclusively of n0radrenergic neurons, interacts with other areas of the CNS (prefrontal cortex, amygdala, hippocampus, hypothalamus, mesolimbic and mesocortical dopaminergic system) that play an important role in information processing, action initiation, as well as setting the emotional tone. We are interested to know the effects of PH on this system involved in the generalized stress response. In the present experiment we have investigated whether PH could affect LC and PVN cellular activity during restraint stress. Expression of the immediate early gene c-fos was used as a marker of neuronal activation. Using Wistar rats, handling was performed once a day between and