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. 2020 Apr 15;40(16):3203–3216. doi: 10.1523/JNEUROSCI.1553-18.2020

Figure 7.

Figure 7.

An increase in h-current contributes to increased TIDA oscillation frequency during lactation. Aa, Whole-cell current-clamp in vitro recording of a DAT-GCaMP3 neuron in the dmArc from a lactating dam; negative current step injected to reveal depolarizing sag indicative of h-current (Ih; magenta trace). Superimposed gray trace represents the same cell recorded in the presence of the Ih-blocker, ZD7288 (50 μm). Sag abolished after pharmacological blockade. Ab, The voltage difference between the sag and the steady state of a hyperpolarizing step is significantly larger in TIDA neurons from lactating dams compared with nulliparous females. ***p < 0.001 (unpaired Student's t test). Ac, The blockage of Ih by ZD7288 decreased the nadir potential in lactating dams (Lac) but not in nulliparous females (Nulli). *p < 0.001 (paired t test). Ba, Representative trace from a whole-cell voltage-clamp recording from DAT-tdTomato neuron in the dmArc from a lactating dam (in the presence of TTX, 500 nm) before (magenta) and during (gray) ZD7288 application (50 μm). Bb, Application of ZD7288 decreased the sag amplitude of Ih in both nulliparous and lactating dam TIDA neurons. *p < 0.05 (paired Student's t test). Bc, I-V curves from nulliparous and lactating dams in the presence or absence of ZD7288. Bd, The comparison of the slope obtained by linear fitting of the I-V curves reveals a difference in lactating dams with respect to nulliparous, which is abolished during Ih blockade by ZD7288. *p < 0.05 (two-way ANOVA with Sidak's multiple comparison as post hoc test). C, Representative traces of Ca2+ fluctuations in a DAT-GCaMP3 neuron before and during ZD7288 application in nulliparous and lactating dam. Box plot represents the effect of bath-applied ZD7288 (50 μm) on the frequency of Ca2+ oscillations in DAT-GCaMP3 neurons from nulliparous and lactating females. In nulliparous, the frequency remains unchanged during pharmacological blockade of Ih (p = 0.77, paired Student's t test); whereas in lactating females, the frequency decreased during ZD7288 application (p = 0.01, paired Student's t test) **p = 0.01. The frequency was significantly different between control conditions without ZD7288 (p = 0.03, unpaired t test).