Figure 2.

Effects of quinine on the firing activity of OT neurons and dye coupling in the SON of brain slices from lactating rats. (A) Firing activity: (Aa) an entire current-clamp recording of the firing activity of an OT neuron; (Ab) expanded episodes within the recording, during, and after treatment with quinine; (Ac) features of spikes at different time points within the expanded episodes. The dashed horizontal lines indicate the peak of the first spike (top line), the level of resting membrane potential (mid line), and the first spike AHP valley (bottom line). The vertical dual arrow indicates the spike amplitude. The horizontal dashed dual arrows (open heads) indicate the full width of AHP at half maximum amplitude (FWHM). Two horizontal arrows mark the FWHM of the action potential duration. (B) Dye coupling: representative images showing magnocellular neurons filled (directly or by coupling) with LY (left) and their immunohistochemical identification as OT neurons in control slices (a) and in slices treated with quinine (0.1 mM, 30 min; b). Merged LY and OT-NP images are shown on the right sides. Scale bar, 20 µm. The preincubation of slices with quinine significantly reduced the incidence of dye coupling between OT neurons when compared with control (n = 7 in each group; 3.43 ± 0.75 OT neurons in control, while 1.43 ± 0.43 when treated with quinine; p = .039 by Student’s t test). Other annotations refer to Figure 1.

OT-NP = oxytocin-neurophysin; LY = Lucifer yellow.