Fig. 6.

Effect of R-type blocker SNX-482 (0.3 μM) on afterhyperpolarizations (AHPs) and their corresponding Ca²⁺ transients in oxytocin (OT) (n = 5) (A–D) and vasopressin (VP) (n = 5) (E–H) neurons. 4-Aminopyridine (4-AP) was preapplied to block Kv4 channels and isolate the effect of SNX482 on R-type Ca²⁺ channels. A: example AHP after a 20-Hz, 20-spike train from an OT neuron and its corresponding somatic Ca²⁺ signal. B: example AHP after a 20-Hz, 5-spike train from an OT neuron and its corresponding somatic Ca²⁺ signal. C: summary data for OT neuron AHP measurements at the 20-spike peak amplitude (medium and slow AHP, mAHP + sAHP), at 1 s after the (sAHP), and 5-spike AHPs at the peak amplitude (mAHP). Red points are individual cells, and black points are group averages. After 20 spikes, 4-AP significantly increased the AHP at peak (*P < 0.05) and 1 s (****P < 0.0001) in 20-spike AHPs. Subsequent application of SNX-482 did not significantly reduce the AHP compared with 4-AP. 5-spike AHPs were unaffected. D: summary data for OT neuron peak Ca²⁺ transients during AHP stimulation in 20-spike AHPs and in 5-spike AHPs. 4-AP increased Ca²⁺ transients significantly in 20-spike and 5-spike trains (*P < 0.05), and successive SNX-482 significantly inhibited the Ca²⁺ signal compared with 4-AP after both 20 and 5 spikes (*P < 0.05). E: example AHP after a 20-spike train from a VP neuron and its corresponding somatic Ca²⁺ signal. F: example AHP after a 5-spike train from a VP neuron and its corresponding somatic Ca²⁺ signal. G: summary data for VP neuron AHP measurements at the 20-spike peak amplitude (mAHP + sAHP), at 1 s after the train (sAHP), and 5-spike AHPs at the peak amplitude (mAHP). Green points are individual cells, and black points are group averages. 4-AP significantly increased the 20-spike AHP at 1 s (***P < 0.001). Subsequent SNX-482 significantly reduced the 20-spike peak and 1-s AHP compared with 4-AP alone (**P < 0.01). 5-spike AHPs were unaffected. H: summary data for VP neuron peak Ca²⁺ transients in 20-spike AHPs and 5-spike AHPs. 4-AP significantly increased Ca²⁺ in the 20-spike (*P < 0.05) and 5-spike (**P < 0.01) protocol. Subsequent SNX-482 significantly decreased Ca²⁺ transients in both 20- (**P < 0.01) and 5-spike AHPs (***P < 0.001). All data were evaluated with a 2-way repeated-measures ANOVA with the exception of the 20-spike Ca²⁺ imaging data. For this data, we used a Friedman’s test because this data did not present a normal distribution.