In the elderly, involuntary passing of urine or incontinence is a common and distressing problem. The external urethral sphincter of the bladder acts as the muscle of continence, and is controlled by the pudendal nerve which carries signals from motoneurones in the Onuf’s nucleus in spinal cord. We hypothesised that in ageing, alteration in the balance between excitatory and inhibitory influence to the motoneurons affects the sphincteric control, especially since there is evidence that the urethral sphincter architecture and volume is unaltered in ageing (Russell et. al., 1996). In this study, we investigated the Onuf’s nucleus homologue known as the dorsolateral nucleus (DLN) in young 3 month old mice, as well as the types and numbers of presynaptic terminals to the DLN motoneurones. Nine wild type female C57BL/6 mice (3 month) were used. In 3 mice, motoneurones innervating the external urethral sphincter were first identified by injection of cholera-toxin B chain (2µl of 1% in saline) under Fluothane anaesthesia. Following 3-5 days recovery animals were anaesthetised with 80mg/kg pentobarbitone IP and perfused with 4% paraformaldehyde (PFA), spinal cord sectioned at 50µm using a vibrating microtome and processed for anti-cholera toxin B chain immunohistochemistry. The location of neurones projecting to the external urethral sphincter was verified using retrograde tracing with cholera-toxin B chain as the DLN in the ventral horn. Six mice were anaesthetised and perfused as above. The sections from 3 mice were stained using choline acetyl transferase (ChAT) and processed for peroxidase immunohistochemistry. The location of ChAT immunoreactive motoneurones was sufficient to distinguish the DLN in the ventral horn, at the level of the sixth lumbar to the first sacral segments of the spinal cord. The mean length of the nucleus was 0.65 ± 0.2 mm, and the mean number of dorsolateral motoneurones was 38.5 ± 1.5 per spinal cord. Spinal cords from 3 mice were processed for triple labelling immunofluorescence for ChAT, glutamic acid decarboxylase (GAD67) and glycine transporter 2 (GlyT2). Quantitative analysis of the immunofluorescence staining by confocal microscopy (Chang and Martin, 2009) revealed that there were 2.0 (± 0.7), 4.4 (± 0.6) and 3.2 ± (0.8) of ChAT-, GAD67- and GlyT2-immunopositive boutons respectively per 100 µm membrane perimeter of motoneurones in the DLN. These initial results will be compared with the findings in aged mice to determine if there are age-related changes on the presynaptic inputs to dorsolateral motoneurones.