As a basis for investigations on motoneuron properties in various transgenic mouse strains we have developed a mouse model for intracellular recording in the adult anaesthetised mouse in vivo. Using an anaesthetic regime of Hypnorm and Midazolam we demonstrate that it is possible to record post-synaptic potentials in motoneurons underlying basic identified circuits in the spinal cord. Forty-one motoneurons with antidromic spike potentials (> 50 mV) from the sciatic nerve were investigated. We recorded the intrinsic properties of the neurones including input resistance (mean 2.4±1.2 M[ohm] ), rheobase (mean 7.1±5.9 nA) and the duration of the afterhyperpolarization (mean 55.3±14 ms). We also measured the minimum firing frequencies (Fmin, mean 23.5 ±5.7 SD Hz), the maximum firing frequencies (Fmax) which could be > 300 Hz and the slope of the current/frequency relationship (f-I-slope) with increasing amounts of current injected (mean 13±5.7 Hz/nA.). Using this anaesthesia signs of activation of persistent inward currents (PICs) were seen, such as accelerations of firing frequency or jumps in the membrane potential with increasing amounts of injected current. This makes this particular preparation an attractive one in which to investigate changes in PICs in transgenic mice. One other aim of the present study was to evaluate the extent to which the properties controlling the firing frequency are tailored to the characteristics of the mouse muscle contraction properties. The present data demonstrates that mouse spinal motoneurons share many of the same properties that have been demonstrated previously for cat, rat and human motoneurons. The shorter AHP duration, steeper f-I slopes and higher Fmin and Fmax are likely to be adaptations to ensure optimal force gradation of muscle unit twitches with contraction times as short as <= 10 ms in the mouse.