Effects of Acute Stress or Centrally Injected Interleukin-1beta on Neuropeptide Expression in the Immune System

Acute stress stimulates the expression and release of corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) from the hypothalamus, and the pro-opiomelanocortin products beta-endorphin and ACTH from the anterior pituitary. These neuropeptides are also expressed in immune tissues, and it has been proposed that they may modulate immune responses to stress through paracrine mechanisms. We subjected rats to restraint stress or central injection of interleukin (IL)-1beta to determine whether these acute stimuli can alter the expression of neuropeptides in the spleen and thymus. Restraint stress significantly increased the contents of all these neuropeptides in thymic, but not splenic, extracts. A single icv injection of IL-1beta increased contents of CRH, AVP, ACTH and beta-endorphin in the spleens of both sham-operated and adrenalectomised (ADX) rats. IL-1beta increased thymic contents of CRH and ACTH in sham-operated rats but these increases were not observed in ADX rats. These results suggest that the effects of IL-1beta on neuropeptide expression in the spleen are independent of glucocorticoids, whereas IL-1beta stimulation of neuropeptide expression in the thymus is dependent on circulating glucocorticoids. There were significant correlations between increases in CRH, ACTH and beta-endorphin in the spleen, and between CRH and ACTH in the thymus, consistent with the suggestion that IL-1beta-induced increases in ACTH and beta-endorphin may be mediated through CRH. These results provide evidence that stressors can directly influence neuropeptide expression in immune tissues. Thus stress may influence immune functions through paracrine mechanisms involving locally synthesised neuropeptides as well as through activation of the hypothalamo-pituitary-adrenal axis.     

Word acquisition, retention, and transfer: findings from contextual and isolated word training

Successful reading instruction entails not only acquiring new words but also remembering them after training has finished and accessing their word-specific representations when they are encountered in new text. We report two studies demonstrating that acquisition, retention, and transfer of unfamiliar words were affected differentially by isolated word and context training. Materials were individualized to include only those words that average readers in second grade were unable to name in context. Different words were trained in each condition; context training presented words in stories, and isolated word training presented words on flashcards. Together, the studies show that context training promotes word acquisition beyond that experienced from reading words in isolation. Contrary to the prevailing opinion, memory performance for words trained in context and in isolation did not differ; children demonstrated excellent retention over an 8-day interval in both conditions. Finally, transfer was maximized when the congruency between training and testing was high. Therefore, when reading trained words in novel circumstances, the best method of training was mediated by the transfer task employed at test.