An increased expression of the mGlu5 receptor protein following LTP induction at the perforant path–dentate gyrus synapse in freely moving rats

• Published in: Neuropharmacology 2003, Vol.44 (1), p.17-25
• Main Authors: Manahan-Vaughan, D., Ngomba, R.T., Storto, M., Kulla, A., Catania, M.V., Chiechio, S., Rampello, L., Passarelli, F., Capece, A., Reymann, K.G., Nicoletti, F.
• Format: Article
• Language: English
• Subjects: 2-Amino-5-phosphonovalerate - pharmacology; Aminoacid receptors (glycine, glutamate, gaba); Animals; Biological and medical sciences; Blotting, Western; Cell receptors; Cell structures and functions; Central nervous system; Central neurotransmission. Neuromudulation. Pathways and receptors; Dentate Gyrus - drug effects; Dentate Gyrus - physiology; Electroencephalography; Evoked Potentials; Fundamental and applied biological sciences. Psychology; Hippocampus; In Situ Hybridization; Injections, Intraventricular; Long-Term Potentiation; LTP; Male; Metabotropic glutamate receptors; Molecular and cellular biology; Perforant Pathway - physiology; Perforant Pathway - ultrastructure; Rats; Rats, Wistar; Receptor, Metabotropic Glutamate 5; Receptors, Metabotropic Glutamate - antagonists & inhibitors; Receptors, Metabotropic Glutamate - metabolism; RNA, Messenger - metabolism; Synapses - physiology; Synaptic Transmission; Vertebrates: nervous system and sense organs
• ISSN: 0028-3908; 1873-7064
• DOI: 10.1016/S0028-3908(02)00342-8

The involvement of metabotropic glutamate (mGlu) receptors in the induction of long-term potentiation (LTP) in vivo has been consistently documented. We have investigated whether LTP induction in the dentate gyrus of rats leads to changes in expression of mGlu2/3 or -5 receptor subtypes in the hippocampus. LTP was induced at the medial perforant path–dentate gyrus synapses, and mGlu receptor expression was examined by Western blot or in situ hybridization. An up-regulation of mGlu5 receptors was observed in the hippocampus both 24 and 48 h following LTP induction. This effect was restricted to the dentate gyrus and CA1 region, whereas no changes in mGlu5 receptor protein (but an increase in mRNA levels) were observed in the CA3 region. The increased expression of mGlu5 receptors was directly related to the induction of LTP, because it was not observed when tetanic stimulation was carried out in animals treated with the NMDA receptor antagonist, 2-amino-5-phosphonopentanoate (AP5). Western blot analysis also showed a reduced expression of mGlu2/3 receptors in the whole hippocampus 24 h after LTP induction, indicating that the increased expression of mGlu5 receptors was specific. These data suggest that an up-regulation of mGlu5 receptors is a component of the plastic changes that follow the induction of LTP at the perforant path–dentate gyrus synapse.