Apelin-13 depolarizes POMC neurons in the ARC.

<p><b>(A)</b> Representative recording sample of the whole-cell membrane potential before, during and after treatment with apelin-13 after having blocked ionotropic glutamate and GABA receptors (left panel). Treatment with apelin-13 (100 nM) induced a depolarization and increased the firing rate of POMC neuron (right panel; mean change in membrane potential: +4.8 ± 0.7 mV, n = 14 neurons, p < 0.05). Scale bar: 20 mV, 2 min. <b>(B)</b> Pooled data of membrane potential and firing rate of POMC neurons with apelin-13 (A-13) (mean membrane potential: before -53.1 ± 2.2 mV vs. after -48.3 ± 1.9 mV, n = 14 neurons, p < 0.05; mean firing rate: before 1.8 ± 0.5 Hz vs. after 2.1 ± 0.6 Hz, n = 9 neurons, p < 0.05). <b>(C)</b> Apelin-13 causes a concentration-dependent depolarization of POMC cells. Depolarization by apelin-13 was determined at 1, 5, 20 and 100 nM in 6, 9, 6 and 14 neurons, respectively. <b>(D).</b> Representative whole-cell recording sample of the electrophysiological effect of apelin-13 in the presence of the APJ receptor antagonist ML221 (20 μM; left panel). Under these experimental conditions, POMC neurons did not respond to apelin-13 (middle and right panels; n = 11 neurons, p > 0.05). Scale bar: 20 mV, 2 min.