<p>The characteristics of spontaneous and evoked neuronal activity are known to undergo changes over time. These changes are typically studied dynamically in acute and subacute experiments (drug-induced anesthesia, the sleep–waking cycle, etc.). Longer-term (weeks, months) recording of the activity of identified neurons is methodologically quite complex. Questions as to whether changes occur, what their nature is, and whether they affect the functional properties of neurons and neuronal populations therefore require further study. In particular, we are not aware that such studies have been conducted at the level of olfactory bulb (OB) neurons, including those related to the perception of odorants at ultra-low concentrations. The aim of the present work was to carry out a longitudinal study of the characteristics of spontaneous activity and activity evoked in identified mitral and tufted neurons (M/T cells) of the olfactory bulb by presentation of odorant vapor (sulcatone) at ultra-low concentrations (~1·10^-15 g/cm³). The activity of OB M/T neurons was periodically (no more than once a week) recorded in five rats for at least one month (maximum 121 days) under xylazine–tiletamine–zolazepam anesthesia. Analysis showed that the characteristics of both spontaneous and odorant-evoked activity of M/T neurons remained stable for quite long periods of time, which is important in terms of conducting research seeking to develop technologies for biohybrid sensory systems for the identification of target substances at ultra-low concentrations.</p>