Cellular Actions of Nesfatin-1 in the Subfornical Organ

Nesfatin-1, a centrally acting anorexigenic peptide, is produced in several brain areas involved in metabolic processes and has been implicated in the control of ingestive behaviours and cardiovascular functions. The present study aimed to determine whether the subfornical organ (SFO), a central nervous system (CNS) site that has been extensively implicated in the regulation of appetite and thirst, may represent a potential site for central actions of nesfatin-1. We first used the reverse transcriptase-polymerase chain reaction and were able to confirm the presence of mRNA for the nucleobindin-2 gene in the SFO. We then used whole-cell patch clamp recordings to investigate the influence of nesfatin-1 on the membrane potential of dissociated SFO neurones. A total of 80.3% (49 of 61) of neurones tested showed a response to nesfatin-1 (100nm, 10nm and 1nm). Of these, 47.5% depolarised, with a mean depolarisation of 8.2 +/- 0.9mV (n=29) and 32.8% hyperpolarised with a mean hyperpolarisation of -8.9 +/- 1.2mV (n=20). Peak magnitudes were seen at a concentration of 1nm nesfatin-1, whereas no effect was observed at 100pm nesftain-1 (n=3). Furthermore, voltage clamp ramp and step protocols revealed a nesfatin-1 induced activation of the delayed rectifier potassium conductance, I-K. Pharmacological blockade of this conductance greatly reduced the magnitude and occurrence of the observed hyperpolarisations. The present study thus demonstrates that nesfatin-1 has the ability to influence the membrane potential of SFO neurones, and thus identifies the SFO as a potential site at which nesfatin-1 may act to regulate ingestive behaviour and cardiovascular control.