Ž . Brain Research 797 1998 342–346 Short communication Changes in IGF-1 receptors in the hippocampus of adult rats after long-term adrenalectomy: receptor autoradiography and in situ hybridization histochemistry A. Islam a , C. Ayer-LeLievre b , C. Heigenskold a , N. Bogdanovic a , B. Winblad a , A. Adem a, ) ¨ a Department of Clinical Neuroscience and Family Medicine, Geriatric Section, Karolinska Institute, Huddinge UniÕersity Hospital, B-84, S-141 86 Huddinge, Sweden b Laboratoire de Biochimie Medicale, URA CNRS, Limoges Cedex, France Accepted 7 April 1998 Abstract Ž . Ž . Alteration of insulin-like growth factor-1 IGF-1 receptor and its mRNA after long-term adrenalectomy ADX was studied in the hippocampus by in vitro receptor autoradiography and in situ hybridization histochemistry, respectively. Significantly, decreased levels of IGF-1 receptor and its mRNA was noted in the dentate and CA1–CA4 regions of the hippocampus of the ADX animals, suggesting that the level and expression of IGF-1 receptors in the hippocampus is influenced by adrenal hormones. q 1998 Elsevier Science B.V. All rights reserved. Keywords: Neurodegeneration; Apoptosis; Corticosteroid; Growth factor Ž . Insulin-like growth factor IGF-1 is a single chain polypeptide which appears to be produced in neurons and w x glial cells throughout the brain 15 and is located in w x various anatomically discrete brain regions 20 . The pres- ence of IGF-1 and its receptor in the adult brain raises the question of their function in mature neuronal and glial w x cells. Sara and Hall 17 have suggested that the IGFs act as neuromodulators by regulating metabolism. Another possible role of IGF-1 in the adult nervous system could wx be related to repair of injury 9 . In the rat hippocampus, both glucocorticoid and IGF-1 receptors are in abundance w x 14,20 . There is evidence that both IGF-1 and glucocorti- w x coids 9,14–16 play important roles in the brain. How- ever, the interaction of steroid hormones with IGF-1 re- mains obscure in the brain although some studies have wx suggested a relation between them 6 . Several groups have shown that ADX and the conse- quent permanent loss of corticosteroids causes neuron loss w x in the hippocampus 3,18 . So far, no information is avail- able about IGF-1 or its receptors in the hippocampus following long-term corticosteroid deprivation. In this ) Corresponding author. Fax: q 46-8-58583880; E-mail: abdu.adem@kfcmail.hs.sll.se study, IGF-1 receptor density was assessed in adult rat hippocampus after ADX. We have used a truncated form of IGF-1 which, under the conditions used in our study, w x will bind specifically to type 1 IGF receptors 2,5 . Fur- thermore, we have used in situ hybridization histochem- istry to detect the changes in the expression of IGF-1 receptor mRNA. Procedures for making adrenalectomy were similar to wx those reported previously 3 . Briefly, bilateral adrenalec- Ž tomy was performed in 10 of the rats male Sprague–Daw- . Ž . ley rats weighing 150–200 g . Age-matched naive five Ž . and sham-operated five rats were used as controls. The operated rats were maintained on food and 0.9% saline solution all through and corticosterone in saline during the first 3 weeks. Five months after surgery, the animals were decapitated. 10-m m thick coronal sections were cut at the level of the habenular commissure, two sections in each slide for each animal, on a cryostat and mounted on chrom–alum gelatin treated slides, and stored at y708C until used for receptor autoradiography or in situ hy- bridization histochemistry. For IGF-1 receptor autoradiography, brain sections were Ž preincubated at q48C in 50 mM Tris–HCl buffer pH s . Ž 7.7 for 10 min. Incubation followed with 25 pM specific . 125 activity 280 Cirmmol I-insulin like growth factor-1 0006-8993r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved.