Phorbol esters potentiate evoked and spontaneous release by different presynaptic mechanisms - PubMed (original) (raw)

Effects of calcium channel antagonists.a, Effects of calcium channel antagonists on evoked release (no PDBu). Data were derived using a 60-stimulus (10 Hz) destaining protocol, after staining using a 100-stimulus train at 10 Hz. Preparations were subjected to two trials, the first a control and the second after or during application of antagonist. ω-CTx-GVIA (1 μ

m

) was applied for 10 min after the second staining step. ω-Aga-IVA (500 n

m

) and nifedipine (10 μ

m

) were each applied for 5 min before the second destaining step and remained in the perfusion chamber during destaining. n: nifedipine, 86; ω-CTx-GVIA, 344; ω-Aga-IVA, 100. b, Calcium channel antagonists failed to attenuate the effect of PDBu on evoked release measured using a 30-stimulus destaining assay (as in Fig. 6_a_). Data are derived from two consecutive trials, the first before and the second after PDBu exposure (as in Fig. 6). Controls were not treated with calcium channel antagonists (n = 391). Nifedipine-treated preparations (n = 279) were perfused throughout with 10 μ

m

nifedipine, beginning 5 min before the start of the first trial. ω-CTx-GVIA effects were examined by pretreating the preparation with 1 μ

m

ω-CTx-GVIA for 10 min before the start of the first trial (n = 194). ω-Aga-IVA (500 n

m

) was applied for 5 min before each staining or destaining stimulus and was also present in the perfusion chamber throughout all destaining stimulus trains (n = 150). c, Influence of antagonists on PDBu-induced potentiation using a 30-stimulus staining protocol (as in Fig. 2_a_). Antagonists were applied as described above (controls,n = 531; 10 μ

m

nifedipine perfused throughout, n = 326; 1 μ

m

ω-CTx-GVIA by pretreatment for 10 min, n = 105; 500 n

m

ω-Aga-IVA by pretreatment for 5 min and perfused throughout stimulation, n = 106). Throughout parts_a–c_, column heights represent medians, and error bars represent the quartile (25–75%) ranges of each distribution.