Cell Signaling · June 23, 2022

Martinez A, Alcantara S, Borrell V, Delrio JA, Blasi J, Otal R, Campos N, Boronat A, Barbacid M, Silossantiago I, Soriano E

Martinez A, Alcantara S, Borrell V, Delrio JA, Blasi J, Otal R, Campos N, Boronat A, Barbacid M, Silossantiago I, Soriano E. 60 min after TBS stimulation. Icariin These results point toward a specific and unique role of endogenous BDNF but not of other neurotrophins in the process of TBS-induced hippocampal LTP. Additionally, they suggest that endogenous BDNF is required for a limited time period only shortly before or around LTP induction but not during the whole process of LTP. Later, several reports demonstrated that acute application of exogenous BDNF, neurotrophin-4/5 (NT4/5), or NT3 can alter or potentiate synaptic transmission in rat hippocampal cultures and slices (Lessmann et al., 1994; Kang and Schuman, 1995;Levine et al., 1995). Nfatc1 Although these experiments indirectly suggested that neurotrophins can participate in synaptic plasticity, work with mice carrying a null mutation in the BDNF gene showed that the lack of endogenous BDNF leads to drastically impaired LTP (Korte et al., 1995;Patterson et al., 1996) and to a limited capability of these animals to perform certain learning tasks (Linnarsson et al., 1997). Importantly, it was also shown that reexpression of the BDNF gene (Korte et al., 1996) or treatment of Icariin slices with recombinant BDNF (Patterson et al., 1996) were both able to restore LTP in slices of these mutant mice within 14 hr, making unspecific developmental deficits unlikely as an explanation for impaired LTP. An additional approach to determine the involvement of endogenous neurotrophins in LTP is to block their function acutely in slices from wild-type animals. Two recent studies used a TrkB-IgG fusion protein (FP) and antibodies (Abs) against the TrkB receptor to block the ligands or the function of the TrkB receptor. This led to impaired LTP in slices from rat hippocampus (Figurov et al., 1996; Kang et al., 1997). Because both BDNF and NT4/5 can interact with the TrkB receptor, these experiments still leave the issue unresolved as to which of the two particular ligands actually contribute to LTP. The situation is further complicated by the fact that TrkB FPs are not selective for BDNF and NT4/5 but also bind NT3 (Shelton et al., 1995). The availability of specific, function-blocking monoclonal antibodies against BDNF and NT3 allowed us Icariin to acutely and selectively interfere with these neurotrophins and to determine their function in hippocampal LTP. We compared their effects on LTP with those of TrkB-IgG FPs and assessed the time period relative to the induction of LTP during which neurotrophins need to be available. MATERIALS AND METHODS Hippocampal transversal slices (400-m-thick) were prepared from male wild-type mice of SV129 strain (4C8 weeks old) using conventional techniques (Korte et al., 1995) and maintained under standard conditions [medium contained (in mm): 124 NaCl, 3 KCl, 1.25 KH2PO4, 2 Mg2SO4, 26 NaHCO3, 2.5 CaCl2, and 10 glucose; at room temperature) and gassed with 95% O2 and 5% CO2. Slices were allowed to recover in an incubation chamber for at least 1.5 hr at room temperature before they were transferred to the perfusion chamber and used for the electrophysiological experiments. The following antibodies were used for LTP experiments: (1) a TrkB receptor body, which is a fusion protein between the extracellular domain of the chick TrkB receptor and the Fc part of a human IgG antibody (Dechant Icariin et al., 1993); (2) a mouse monoclonal antibody (MAB) (clone #21, IgG2B) raised against BDNF, characterized by its function blocking action with the same specificity as MAB clone #9 described by Kolbeck et al. (1999); and (3).