The regulatory role of central neuropeptide-S in locomotion.

Central exogenous Neuropeptide-S (NPS) was demonstrated to increase locomotor activity (LMA) in rodent studies. NPS receptor (NPSR) is produced in locomotion-related brain regions including basal ganglia while NPS mediates dopaminergic neurotransmission suggesting that endogenous brain NPS is involved in the regulation of locomotion. Aim of the study was to elucidate whether antagonism of NPSR impairs locomotion and to determine the neurochemical profile of NPSR-expressing cells in basal ganglia network. In the rats received intracerebroventricular injection of selective non-peptide NPSR antagonist ML154 (20 nmol/5 µL) or vehicle, in addition to measurement of catalepsy, motor performance, and motor coordination were evaluated by assessment of LMA and RR test, respectively. The immunoreactivities for NPSR, tyrosine hydroxylase (TH), glutamate decarboxylase 67 (GAD67), and choline acetyltransferase (ChAT) were detected by immunofluorescence in frozen sections. Compared to the control rats, total LMA was significantly declined following ML154 administration. The ML154-injected rats were more prone to fall in rotarod (RR) test, while they exhibited remarkably high catalepsy time. The most robust immunoreactivity for NPSR was detected in globus pallidus externa (GPe), while moderate levels of NPSR expression were observed in substantia nigra pars compacta (SNpc) and ventral tegmental area (VTA), but not in striatum. The NPSR-ir cell bodies were found to express GAD67 in GPe and TH in SNpc and VTA, respectively. NPSR expression was detected in SNpc-projecting pallidal cells. The present findings indicate the regulatory role of central endogenous NPS in the control of locomotion. NPSR may be a potential therapeutic target for the treatment of movement disorders.