2004), amyotrophic lateral sclerosis (Ghadge et al. DRG, satellite cells were positive for GLT1 and GCPII, whereas sensory neurons were positive for EAAC1. GLAST was localized in both neurons and satellite cells. In the sciatic nerve, GLT1 and GCPII were expressed in the cytoplasm of Schwann cells, whereas GLAST and EAAC1 stained the myelin layer. Our results give for the first time a complete characterization of the glutamate transporter system in the peripheral nervous system. Therefore, they are important both for understanding glutamatergic signalling in the PNS and for establishing new strategies to treat peripheral neuropathies. Keywords:glutamate, glutamate transporters, immunoblotting, immunohistochemistry, peripheral nervous system == Introduction == l-Glutamate is Lofexidine the major excitatory neurotransmitter in the mammalian central nervous system (CNS) that contributes to fast synaptic neurotransmission. It is involved in complex physiological processes such as memory, learning and plasticity. Recently, glutamate has been shown to have a role also in the transduction of sensory input at the periphery, and in particular in nociceptive transmission (Carlton, 2001). An excess of glutamate, however, is frequently correlated with neurotoxicity and neuronal cell death (Ozawa et al. 1998;Dingledine et al. 1999) and, consequently, it is also implicated in a number of neurological disorders including peripheral neuropathies (Watkins, 2000). For these reasons, therapeutic approaches for treating these diseases have attempted to block glutamate receptors with small antagonist molecules. The mechanism of action of these drugs is believed to be the inhibition of the effects of excitatory aminoacids and intracellular calcium accumulation (Kawamata & Omote, 1996). However, severe side effects have limited the clinical use of such glutamate antagonists (Yashpal et al. 2001;Fisher et al. 2002;Cvrcek, 2008). On the other hand, reducing glutamate synthesis through the inhibition of glutamate carboxypeptidase (GCPII), the enzyme that generates glutamate from N-acetyl-aspartyl-glutamate (NAAG), protects against neurodegeneration and disease progression in Lofexidine multiplein vitroandin vivomodels of neurological disorders, including peripheral neuropathies (Bacich et al. 2005). In addition, it appears that GCPII is exclusively recruited to provide a source of glutamate in hyperglutamatergic, excitotoxic conditions and would, therefore, be devoid of the side effects of glutamate antagonist drugs (Zhang et al. 2006). This has been Lofexidine clinically confirmed by exposing patients to GCPII inhibitors at presumed therapeutic doses Lofexidine (van der Post et al. 2005). In animal models, GCPII inhibitors reduce neuropathic pain and ectopic discharges from injured nerves but with slight central sensitization in inflammatory and injury-induced neuropathies (Yamamoto et al. 2001;Carpenter et al. 2003;Yamamoto et al. 2004). These data are in agreement with previous reports that show Lofexidine the ability of GCPII inhibitors to prevent pain, nerve conduction velocity reduction and nerve degeneration in diabetic BB/Wor rats (Zhang et al. 2002). Despite all these therapeutic attempts, little is known about the basic features of the glutamatergic system in the peripheral nervous system (PNS). There is now growing evidence that glutamate may have a signaling function together with acetylcholine at the vertebrate neuromuscular junction Rabbit Polyclonal to WAVE1 (phospho-Tyr125) (NMJ) (Rinholm et al. 2007). Some glutamate transporters (i.e. GLAST and GLT1) are located in the postsynaptic muscle membrane of the NMJ of skeletal muscle and their presence could also be hypothesized in the Schwann cells, although with a lower density than in the postsynaptic sarcolemma. In agreement with the well-known CNS localization, the expression of GLAST, GLT1 and the neuronal glutamate transporter EAAC1 has also been detected in rat optic nerve (Choi & Chiu, 1997). In addition, GLAST and EAAC1 seemed to be expressed in the glial and neuronal component, respectively, of dorsal root ganglia (DRG), although these results are not conclusive (Berger & Hediger, 2000;Tao et al. 2004). A deeper knowledge of the pattern of expression and localization of glutamate transporters and GCPII in normal PNS would allow these molecules to be used as a target for pharmacological compounds. The aim of this study is to characterize the expression and the distribution of glutamate transporters GLT1,.
