When recorded on olfactory bulb slices, mitral cells display a continuum of spiking patterns going from bursting to regular spiking (Angelo et al., 2011; Yu et al., 2015). Besides, Hyperpolarization-activated cationic current (Ih) expression is widely heterogeneous among mitral cells (Angelo et al., 2011; Angelo et al., 2012). Previous in vitro studies suggest that Ih expression in mitral cells is correlated with a regular spiking pattern and an increased intrinsic excitability (Angelo et al., 2011; Burton et al., 2014). However, the causal role of Ih on mitral cell spiking remains elusive and has not been explored in vivo. We explored this question by performing both in vitro and in vivo recordings of mitral cells using respectively patch clamp on OB slices and sharp electrodes intracellular recordings in young adults rats (P42-P70). We found a similar distribution of Ih expression in our in vivo and in vitro recordings. More importantly, we unveiled a positive covariation between Ih and spike afterhyperpolarization (AHP) both in vitro and in vivo. Consequently, Ih magnitude predicts intra-burst spiking frequency of mitral cells recorded in vitro. However, Ih blockade by ZD7288 has no effect on spike AHP charge. Therefore, Ih seems to be a good predictor of mitral cells firing properties but the mechanisms underlying this phenomenon remain elusive. Experiments: We used both in vivo intracellular recordings and in vitro patch clamp recordings in order to investigate the potential effect of Ih on mitral cells firing.