Neuroscience Research 79 (2014) 94–98 Contents lists available at ScienceDirect Neuroscience Research jo ur nal home p age: www.elsevier.com/locate/neures Rapid Communication Reorganization of sensory pathways after neonatal hemidecortication in rats Oraphan Wanakhachornkrai a,b,c , Tatsuya Umeda a,∗ , Kaoru Isa a , Mayuree H. Tantisira d,e , Boonyong Tantisira d,f , Tadashi Isa a,g,h a Department of Developmental Physiology, National Institute for Physiological Sciences (NIPS), National Institutes of Natural Sciences (NINS), Myodaiji, Okazaki, Japan b Physiology Unit, Department of Medical Sciences, Faculty of Sciences, Rangsit University, Pathumthani, Thailand c Inter-disciplinary Program of Physiology, Graduate School, Chulalongkorn University, Bangkok, Thailand d Faculty of Pharmaceutical Sciences, Chulalongkorn University, Bangkok, Thailand e Faculty of Pharmaceutical Sciences, Burapha University, Chonburi, Thailand f Faculty of Pharmacy, Silpakorn University, Nakhonpathom, Thailand g School of Life Science, The Graduated University for Advanced Studies (SOKENDAI), Hayama, Japan h Core Research for Evolutionary Science and Technology (CREST), Japan Science and Technology Agency (JST), Kawaguchi, Japan a r t i c l e i n f o Article history: Received 23 October 2012 Received in revised form 16 October 2013 Accepted 8 November 2013 Available online 16 November 2013 Keywords: Lemniscus pathway Biotinylated dextran amine Plasticity Hemidecortication a b s t r a c t We investigated ascending somatosensory pathways in neonatally hemidecorticated rats. Injection of an anterograde tracer, biotinylated dextran amine (BDA), into the contralesional dorsal root ganglions revealed ipsilateral projections to the dorsal column nuclei (DCN) in hemidecorticated rats as well as in normal rats. Injection of BDA into the DCN on the same side revealed that while most axons projected to the contralateral thalamus, some axons were detected in the ipsilateral thalamus in hemidecorticated rats while such projections were rarely detected in normal rats. The results suggest that aberrant ipsilateral projections of DCN neurons contralateral to the lesion developed after the hemidecortication. © 2013 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved. Juvenile brains have a higher capacity to adapt to injury than adult brains. Rats with hemidecortication at the neonatal stage exhibit fairly normal forelimb movements on the side contralat- eral to the lesion (Barth and Stanfield, 1990; Hicks and D’Amato, 1970, 1975; Takahashi et al., 2009). Such extensive, early brain damage is compensated for by large-scaled reorganization of the corticofugal connections from the undamaged sensorimotor cortex to the ipsilateral motoneurons to restore normal motor function of the forelimb contralateral to the lesion (Barth and Stanfield, 1990; Castro, 1975; Hicks and D’Amato, 1975; Kartje-Tillotson et al., 1986; Leong, 1976; Leong and Lund, 1973; Nah and Leong, 1976a,b; Naus et al., 1985; Rouiller et al., 1991; Takahashi et al., 2009; Umeda et al., 2010; Umeda and Funakoshi, 2013). Despite a considerable number of studies on the plasticity of the corticofugal pathways, the ascending somatosensory path- ways in hemidecorticated rats have been poorly studied. Neonatal ∗ Corresponding author. Present address: Department of Neuroanatomy, Grad- uate School of Medicine, Yokohama City University, 3-9 Fukuura Kanazawa-ku, Yokohama 236-0004, Japan. Tel.: +81 45 787 2571; fax: +81 45 782 7251. E-mail addresses: tumeda@yokohama-cu.ac.jp, umeda@nips.ac.jp (T. Umeda). hemidecorticated rats exhibit responses to tactile stimulation of the forelimb contralateral to the lesion, although the threshold of sensation in the forelimb on this side is rather high compared to the forelimb on the other side (Schallert and Whishaw, 1984, 1985). The undamaged sensorimotor cortex receives projections only from thalamic neurons on the ipsilateral side, as in normal rats (Sharp and Gonzalez, 1986). Thus, it is still unclear how hemidecorticated rats process tactile and proprioceptive inputs from the periphery contralateral to the lesion. In this study, we analyzed ascending pathways in the dorsal lemniscal system coursing from the dorsal root ganglion (DRG) neu- rons to the thalamic nucleus in hemidecorticated rats. Fourteen normal and 14 hemidecorticated Wistar rats were used through- out the experiments. For hemidecortication, the right hemisphere including the sensorimotor cortex of 5 day-old-rats was aspirated as previously described (Takahashi et al., 2009; Umeda and Isa, 2011; Umeda et al., 2010). The pups were then returned to their mother and separated by gender after weaning day. At adulthood (4–7 months old), the rats were used in the following experiments. First we investigated projections of DRG neurons to the dorsal column nuclei (DCN). After anesthesia with a cocktail of xylazine (10 mg/kg; Bayer Health Care, Monheim, Germany) and ketamine 0168-0102/$ – see front matter © 2013 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved. http://dx.doi.org/10.1016/j.neures.2013.11.003