Figure 2.

Oxytocin (OXT)-induced Ca²⁺ signaling in oscillating hypothalamic primary neurons is mediated by the plasma membrane ion channels. OXT effects on intracellular Ca²⁺ concentration ([Ca²⁺]_i) of an oscillating (a) and a non-oscillating (b) neuron. Stimulation with 100 nM OXT evokes a [Ca²⁺]_i response in the oscillating, but not in the non-oscillating cell. (c) OXT increases basal [Ca²⁺]_i, increases amplitudes (ampl), and decreases frequency (freq) of oscillations. Data are presented as mean+SEM. *P<0.05 compared with control (100%). (d and e) Under extracellular Ca²⁺-free conditions (EGTA, 25 mM), Ca²⁺ oscillations disappear and OXT (100 nM) has no further effect on [Ca²⁺]_i. (d) Representative trace. (e) Quantification of [Ca²⁺]_i, oscillation amplitude, and frequency in response to chelating of extracellular Ca²⁺ and OXT application in eight cells. Data are expressed relative to pre-drug, basal levels (basal, 100%), and presented as mean+SEM. *P<0.05. (f) La³⁺-sensitive Ca²⁺channels mediate the Ca²⁺oscillations and the action of OXT on [Ca²⁺]_i. Extracellular application of La³⁺ (100 μM) decreases [Ca²⁺]_i, and oscillation amplitude and frequency. There is no further effect of OXT (100 nM) on these parameters. Each line represents a single neuron.