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. Author manuscript; available in PMC: 2020 Oct 15.
Published in final edited form as: Brain Res. 2019 Jul 23;1721:146346. doi: 10.1016/j.brainres.2019.146346

Figure 4.

Figure 4.

PBG responses profiles. Summary data for 1 μM PBG is in the left column while responses to 10 μM PBG are on the right. The majority of afferents had 5-HT3 receptors on both the axon and the terminal (Latency and Basal, light blue). Overall, PBG affected latency (white + light blue) in a greater number of afferents than basal glutamate (dark blue + light blue) release from the terminal. Only data from cells with significant changes in the indicated glutamate release mode are included (i.e. cells without a PBG-induced change in basal rates were not included in the basal summary data). A, 1 μM PBG (grey bar) increased basal glutamate rates of sEPSCs in the first second prior to stimulation by ~200% (p = 0.03, paired t test, n = 7). Basal sEPSC amplitudes did not change (p = 0.8, paired t test) indicating presynaptic location of the receptor. Asynchronous rates are only present with successful ST-EPSCs. In this data set, only 3 neurons still had measurable evoked release after 10 min PBG (see inclusion requirements in methods). In those neurons, asynchronous rates were unchanged (p = 0.2, paired t test). B, In neurons exposed to 10 μM PBG, glutamate from the spontaneous vesicle pool increased over 350% (paired t test, p < 0.001, n = 13). In this subset, there were 3 neurons that met the inclusion requirements for accurate asynchronous release measurements. Similar to 1 μM, asynchronous glutamate was unaffected (p = 0.1, paired t test). C, In 3 neurons with measurable amplitudes after 10 min of 1 μM PBG, ST-EPSC amplitude was not changed (p = 0.7, paired t test) despite increased latency (p < 0.01, paired t test, n = 8). D, Similar to results in 1 μM PBG, 10 μM did not change ST-EPSC amplitude (p = 0.2, paired t test, n = 11) but increased latency an average of 450 μs (p = 0.002, paired t test, n = 10), similar to the changes at 1 μM (p = 0.3). While a higher concentration of PBG resulted in a more robust increase in sEPSCs from the basal pool (p = 0.01, t test), it still did not affect the evoked or asynchronous vesicle pools.