a, Representative trace of an LHb neuron transformed from bursting to tonic-firing mode with a ramp-like current injection, showing bursting at more hyperpolarized potentials and tonic firing at more depolarized potentials. Spikes in bursting and tonic-firing mode are shown in blue and black, respectively. b–d, Correlations of membrane potential with intra-burst frequency (b), burst duration (c) and intra-burst spike number (d) generated by current ramps. n = 104 neurons, 14 rats. e, f, Example traces of a spontaneously tonic-firing neuron transformed to burst-firing mode by hyperpolarization (e), and a spontaneously bursting neuron transformed to tonic-firing mode by depolarization (f). g–k, Example traces (left) and statistics (right) showing effects of ketamine (g), AP5 (h), mibefradil (i), ZD7288 (j) and fluoxetine (k) on rebound bursts induced by a transient hyperpolarizing current step. Current injection steps are illustrated under the bottom of the trace. n = 9 neurons, 2 rats (g); n = 12 neurons, 5 rats (h); n = 14 neurons, 2 rats (i); n = 8 neurons, 3 rats (j); n = 6 neurons, 2 rats (k). Data are mean ± s.e.m.; *P < 0.05, ****P < 0.0001, n.s., not significant. Two-tailed paired t-test.