Activation of neuronal nicotinic receptors leads to
downregulation of the EPP quantal content
Under control conditions, the quantal content (QC) was 46.8 ± 4.5. The
bath application of nicotine (10 µM) decreased the QC of EPP
significantly by 12.0 ± 4.4% (n = 5, 7 NMJs; Figure 2).
The nicotine-induced decrease in the number of ACh quanta released in
response to stimulation of the motor nerve suggests the involvement of
presynaptic cholinergic receptors. Using the antagonist of neuronal
nicotinic ACh receptors (nNAChRs) DHβE (Moroni et al., 2006; Wonnacott,
2014), we obtained the data supporting this suggestion. Application of
DHβE alone at a concentration of 1 μM did not change the QC of EPP
(101.5 ± 1.3%; n = 6, 9 NMJs, Figure 2), however, after the
pretreatment with DHβE, the inhibitory effect of nicotine on the quantal
release of ACh was completely abolished (105.5 ± 6.6%; n = 6, 9 NMJs;
Figure 2).