BEHAVIORAL NEUROSCIENCE The paraventricular nucleus of the hypothalamus is a neuroanatomical substrate for the inhibition of palatable food intake by neuropeptide S Amalia Fedeli, 1 Simone Braconi, 1 Daina Economidou, 1 Nazzareno Cannella, 1 Marsida Kallupi, 1 Remo Guerrini, 2 Girolamo Calo `, 3 Carlo Cifani, 1 Maurizio Massi 1 and Roberto Ciccocioppo 1 1 Department of Experimental Medicine and Public Heath, University of Camerino, Via Scalzino 3, 62032, Camerino, Italy 2 Department of Pharmaceutical Sciences and Biotechnology Center, Section of Pharmacology, University of Ferrara, Ferrara, Italy 3 Department of Experimental and Clinical Medicine, Section of Pharmacology and Neuroscience Center, University of Ferrara and National Institute of Neuroscience, Italy Keywords: CRF, hypothalamus, neuropeptide S, palatable food, rat Abstract Neuropeptide S (NPS) is a recently discovered neurotransmitter that binds to its cognate G-protein coupled receptor, NPSR. Previous studies have shown that central administration of this peptide induces anxiolytic-like effects, promotes arousal and inhibits feeding in the same dose range. In the present study, we sought to investigate further the unique physiopharmacological profile of the NPS system by characterizing its effects on palatable food consumption in rats and comparing it with the effect of the classical anxiolytic benzodiazepine midazolam. The results demonstrated that midazolam (5.0 or 10.0 mg ⁄ kg) increases palatable food consumption, while intracerebroventricular (ICV) administration of NPS markedly reduces it. The anorectic effect of NPS (0.1– 1.0 nmol per rat, ICV) was prevented by ICV pretreatment with the NPSR antagonist [d-Cys(tBU) 5 ]NPS (20.0–60.0 nmol per rat). Pretreatment with the nonselective corticotrophin-releasing factor receptor (CRF) antagonist alpha-helical CRF 9–41 (6.25 and 12.5 nmol per rat) completely reversed the hypophagic action of CRF (0.4 nmol per rat, ICV) but did not prevent the anorectic effect of ICV NPS (1.0 nmol per rat). Brain site-specific microinjection experiments revealed that NPS markedly inhibits palatable food intake if administered into the paraventricular nucleus of the hypothalamus (PVN). A similar but smaller and shorter lasting reduction of feeding was observed following intra-lateral hypothalamus administration, whereas no effect was observed following injection into the central amygdala. The present study demonstrates that NPS evokes a potent inhibition of palatable food consumption and that the PVN is an important site of action for its effect. Introduction Neuropeptide S (NPS), a 20-amino-acid peptide, has been recently identified, through a reverse pharmacology approach, as the endog- enous ligand of the orphan G-protein coupled receptor GPR154, now referred to as NPS receptor (NPSR) (Sato et al., 2002; Xu et al., 2004). The primary structure of NPS is highly conserved across species; its name is related to the N-terminal serine that is present in all species analysed thus far (Sato et al., 2002; Xu et al., 2004). Brain in situ hybridization has shown that the NPS mRNA is expressed mostly in two brain areas, a group of previously undescribed neurons located between the locus ceruleus (LC) and the Barrington nucleus, and in the parabrachial nuclei. In the area between the LC and the Barrington nucleus, NPS mRNA is predominantly expressed in glutamatergic cells, whereas in the parabrachial area, expression overlapping with corticotrophin-releas- ing factor (CRF)-positive neurones has been documented (Xu et al., 2004, 2007). NPSR mRNA is expressed throughout the central nervous system, with the highest concentration found in olfactory structures, in the amygdaloid complex, the subiculum, the lateral, dorsomedial and ventromedial hypothalamus, and in the paraventric- ular hypothalamic nucleus (Xu et al., 2004, 2007). NPS binds the NPSR at nanomolar concentrations (K d = 0.3 nm) and activation of this receptor results in a transient increase in intracellular free Ca 2+ , indicating that this neuropeptide may behave as an excitatory neurotransmitter in vivo (Xu et al., 2004). Consistent with this, central administration of NPS has been shown to produce long-lasting arousal, by increasing wakefulness, and to stimulate locomotor activity in both naı ¨ve and habituated mice in the open field test (Xu et al., 2004; Reinscheid et al., 2005). Interestingly, after central injection, NPS stimulated locomotion and produced an anxiolytic-like effect at the same doses in a variety of experimental paradigms such as the light–dark box, the elevated plus maze, the open field and the marble burying tests (Xu et al., 2004; Leonard et al., 2008; Vitale et al., 2008). Recently, it has been demonstrated that intracranial Correspondence: Dr R. Ciccocioppo, as above. E-mail: roberto.ciccocioppo@unicam.it Received 31 March 2009, accepted 18 August 2009 European Journal of Neuroscience, Vol. 30, pp. 1594–1602, 2009 doi:10.1111/j.1460-9568.2009.06948.x ª The Authors (2009). Journal Compilation ª Federation of European Neuroscience Societies and Blackwell Publishing Ltd European Journal of Neuroscience