Cerebrospinal fluid-contacting neurones (CSFcNs) are located in the subependymal layer surrounding the central canal of the spinal cord, an area recently defined as an adult neurogenic niche (Hamilton et al., 2009). The close proximity of CSFcNs to the neural stem cells in this niche, combined with the increasing evidence that they are immature neurones (Marichal et al., 2009) suggests that CSFcNs could be a product and/or a regulator of neurogenesis within the adult spinal cord. To understand the role of CSFcNs, it is important to define which neurotransmitters they respond to and to characterise such responses. This work aims to determine whether 5HT and GABA can influence the activity of CSFcNs. To achieve this, spinal cord slices were obtained from Wistar rats (9 days old) and C57B6 mice (9-12 days old) for whole cell patch clamp recordings (Deuchars et al., 2001). Anaesthesia was produced by I.P administration of urethane (2g/kg) or sodium pentobarbitone (60mg/kg) for rats and mice, respectively. For current clamp recordings the drugs GABA (200 µM) and 5HT (10-20 µM), were bath applied to slices. Drug effects were determined using one-way ANOVAs to compare the input resistance and membrane potential measured before, during and after drug application. GABA significantly decreased the input resistance recorded from CSFcNs in both rats (n=7; p<0.01) and mice (n=3; p<0.05). At holding potentials of -45mV, GABA either depolarised (n=3) or hyperpolarised (n=4) rat CSFcNs. Both bicuculline and gabazine antagonised these responses. For immunohistochemistry, transgenic mice expressing GFP in cells under control of the promoter for glutamic acid decarboxylase 67 to label CSFcNs were used. Adult mice were anaesthetised by I.P administration of sodium pentobarbitone (60mg/kg) and perfused with 4% paraformaldehyde before removal and sectioning of the spinal cord. Rat anti-5HT (1:200; Chemicon) was used as the primary antibody. Immunohistochemistry revealed 5HT-containing terminals in close apposition to GFP positive CSFcNs, however 5HT had no effect on either the input resistance or membrane potential of CSFcNs in rats (n=3; p=0.997) and mice (n=4; p=0.982). These results are the first to demonstrate that mice CSFcNs express GABA receptors, and confirm previous reports of GABA receptors on rat CSFcNs (Marichal et al., 2009). This suggests that the ability of GABA to influence CSFcNs may be conserved throughout mammalian species. The discovery of 5HT-containing terminals apposing CSFcNs would imply that 5HT is endogenously released on to CSFcNs. The lack of response observed to single applications of 5HT will be further investigated to determine whether repeated applications of 5HT elicit a response or whether 5HT modulates the response of CSFcNs to other neurotransmitters.