We also show that large events decrease in number following the addition of adenosine or increase following addition of 4-AP. We utilized this new technique to test whether pr changes after the induction of LTP, as we and others have previously reported (Antonova et al.,

2001, Bolshakov and Siegelbaum, 1994, Enoki et al., 2009, Malgaroli et al., 1995 and Zakharenko et al., 2001). We find that LTP produces an increase in the incidence of large Ca2+ events at some but not all boutons to a single round of LTP (Figure 12C). A second round of LTP increased pr at boutons that had Venetoclax previously not shown an increase or increased further the incidence of large Ca2+ events at boutons that had previously shown Selleckchem INCB018424 an increase. These data are consistent with previous work in which LTP produces an increase in pr at active synapses (Emptage et al., 2003 and Enoki et al., 2009) but does not show an increase in pr at silent synapses (Emptage et al., 2003 and Ward et al., 2006). However, silent synapses once unmasked by LTP do show an increase in pr. These data also reveal that multiple rounds of LTP are able to repeatedly

increase pr at active synapses. This not only illustrates how heterogeneity of pr might be achieved but also has implications for information storage, because it illustrates that synapses are not bistable elements but instead serve as graded storage devices capable of repeatedly updating transmission efficacy. Transverse 350 μm hippocampal organotypic heptaminol slices were prepared from male Wistar rat pups, postnatal day 7 (Harlan UK) as previously described (Emptage et al., 1999 and Stoppini et al., 1991). Each slice was maintained in culture for 7–14 days

prior to use. Slices were transferred to a recording chamber (Scientific Systems Design) mounted on an Olympus BX50WI microscope with a BioRad Radiance 2000 confocal scanhead (BioRad/Zeiss) and were superfused at 30°C with oxygenated ACSF as described previously (Ward et al., 2006). Whole-cell patch clamp and sharp microelectrode recording techniques were used in the study, and the data were collected using WIN WCP software (Strathclyde Electrophysiology Software). The criteria employed for identifying axons and boutons has previously been characterized using synaptophysin staining (Emptage et al., 2001). In brief, the Oregon green 488 fluorescence allowed the identification of axons according to the following criteria: thin shaft (as opposed to dendrites), tortuous trajectory, and distinct varicosities in the absence of dendritic spines. The boutons selected were located 75–300 μm and at least two branch points distal to the initial axon segment for pharmacological characterization. Line scans were synchronized to intrasomatically stimulated APs triggered by injecting current (∼0.5–2.5 μA) with a stimulus duration of 30 μs.