• . .. | ELSEVIER Molecular Brain Research 35 (1996) 269-277 MOLECULAR BRAIN RESEARCH Research report Differential expression of a-CGRP and ¢I-CGRP genes within hypoglossal motoneurons in response to axotomy Manuel Sarasa a,*, Jos~ Terrado a, Guadalupe Mengod u, Salvador Climent a, Pedro Muniesa a Jos6 M. Palacios b a Department of Anatomy, Embryology and Genetics, Faculty of Veterinary Sciences, University ofZaragoza, Miguel Servet 177, E-50013 Zaragoza, Spain b Department of Neurochemistry, Center of Investigation and Development, CSIC, Jordi Girona 18-26, E-08034 Barcelona, Spain Accepted 22 August 1995 Abstract In this study we have analysed, by in situ hybridization, the expression of the genes for both a-CGRP and /3-CGRP in hypoglossal motor nuclei following transection of the left hypoglossal nerve. Our results show that the gene for a-CGRP displays a peculiar sequence of regulation (a successive up-down-up-recovery sequence) within ipsilateral hypoglossal motoneurons in response to axotomy. It is initially up-regulated, then down-regulated (displaying mRNA levels below basal), and later again up-regulated before recovery• By contrast, the gene for/3-CGRP displays a successive and distinct up-down-recovery sequence of regulation (it does not display a second increase in mRNA production). The first up-regulation of the a-CGRP gene occurs just during the early period of perineuronal glial reaction and the second up-regulation just during the period of delayed astrocyte reaction and muscle reinnervation. Because a-CGRP is a neuron-derived factor for many types of cells, including astrocytes and skeletal myocytes, our results suggest that the pleiotropic a-CGRP may be a motoneuron-derived trophic signal for both glial and skeletal muscle cells in order to maintain the motoneuron itself and, in consequence, might be of therapeutic interest in treating degenerative diseases of motoneurons. /3-CGRP might be redundant within the hypoglossal motoneurons. Keywords: a-CGRP; /3-CGRP; Gene expression; In situ hybridization; Axotomy; Neuron regeneration; Motoneuron; Neurotrophic factor: Hypoglossal nucleus; Rat 1. Introduction As response to axotomy, motoneurons undergo a rapid reaction to injury, which is accompanied by a perineuronal glial reaction or gliosis. Then, if reversible, sequential periods of axon outgrowth, re-establishment of functional contact with the target (muscle) and axon maturation oc- cur. These periods are accompanied by a number of struc- tural and molecular changes which reflect a re-ordering of metabolic priorities so that the synthesis of trophic factors or growth-associated proteins is augmented while that of neurotransmitters, receptors and other components of the usual machinery is decreased [7,18,26,27,52]. For example, • Corresponding author. Fax: (34) (76) 761605. 0169-328X/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved SSDI 0l 69-328X(95)00224-3 following axotomy, motoneurons stimulate protein synthe- sis and glucose utilization [44,46] and up-regulate the genes for cytoskeletal proteins as actin and tubulin [37,50,51], for the growth-associated protein GAP-43 [13,36,45,51], for the nerve growth factor receptor [4,11,23], or for the different isoforms of the fl-amyloid precursor protein [48]. By contrast, they down-regulate the genes for choline acetyltransferase and acetylcholineste- rase, the acetylcholine synthesizing and degrading en- zymes, respectively [4,9,11,52,53], for the a and /3 sub- units of glycine receptor ([35,41]; Sarasa et al. unpublished results), for muscarinic [39,40] and nicotinic [43] acetyl- choline receptors, or for cytoskeletal neurofilament pro- teins [50,51]. The above-mentioned rule, however, seems not to affect peptide neurotransmitters such as calcitonin gene-related peptide (CGRP), galanin, or cholecystokinin.