Fig. 3
An excitatory inward current was revealed when α-synM was applied during blockade of presynaptic transmission, or antagonism of GABAA, GABAB and glycine receptors, suggesting that α-synM induces an outward membrane current in LDTF neurons due to actions at presynaptic inhibitory neurons. A) Sample of membrane responses to α-synM in which an inward current is revealed when α-synM is applied in presence of (A1) TTX, (A2) low calcium solution, or (A3) a cocktail of SR-95,531 + CGP-55,845 + strychnine, which block GABAA, GABAB and glycine receptors, respectively). (B) Histograms from a population of cells recorded in which there were significant changes in the (B1) polarity of the evoked membrane current responses to α-synM in presence of TTX, low calcium solution or GABA and glycine receptor antagonists when compared to control responses (Fisher’s Exact test). (B2) The amplitude of the current evoked by α-synM in control conditions and under conditions of synaptic blockade and inhibitory receptor antagonists is shown revealing the change in polarity of the α-synM induced current. (B2, Inset) Graphs of holding currents before and after application of α-synM to LDTF showed that in presence of TTX, low calcium solution, and GABAA, GABAB, and glycine receptor antagonists, holding currents became significantly more negative after application of α-synM, which reflected the α-synM-mediated induction of inward currents. (C) The decrease in intracellular calcium in LDTF is mediated, at least in part, by inhibitory receptors as illustrated in this histogram showing data from the population of LDTF cells recorded that showed a significantly smaller decrease in the amplitude of intracellular calcium induced by α-synM in presence of SR-95,531, CGP-55,845 and strychnine when compared to control conditions (Control: n = 52, GABA/Gly antagonists: n = 49; p = 0.0001; Paired T-test). LDTF: Laterodorsal tegmental nucleus of female. * Indicates p < 0.05, ** Indicates p < 0.01, *** Indicates p < 0.001