Substance P exerts its various biochemical effects mainly via interactions through neurokinin-1 receptors (NK1). Recently, the NK1 receptor has attracted considerable interest for its possible role in a variety of psychiatric disorders including depression and anxiety. However, little is known regarding the anatomical distribution of NK1 in the human central nervous system (CNS). Riboprobe in situ hybridization, quantitative PCR and in vitro autoradiography were performed. Highest NK1 mRNA levels were localized in the locus coeruleus and ventral striatum, while moderate hybridization signals were observed in the cerebral cortex (most abundant in the visual cortex), hippocampus and different amygdaloid nuclei. Very low levels of the NK1 mRNA were detected in the cerebellum and thalamus. In view of the existence of a long and short isoform of the NK1 receptor, it was of interest to assess whether there was a differential distribution of the two splice variants in the human CNS and peripheral tissues. A quantitative TaqMan PCR analysis showed that the long NK1 isoform was the most prevalent throughout the human brain, while in peripheral tissues the truncated form was the most represented. 3H-Substance P autoradiography revealed a good correlation between receptor binding sites and NK1 mRNA expression throughout the brain, with the highest levels of binding in the locus coeruleus. These results provide the anatomical evidence that the NK1 receptors have a strong association with neuronal systems relevant to mood regulation and stress in the human brain, but do not suggest a region-specific role of the two isoforms in the CNS.

Pharmacological results suggest that this model, in addition to face validity as an isomorphic model of human binge eating, is endowed with good predictive validity.

3 Following a constant rate iv infusion to steady state in rats, SB-656104 had a blood clearance (CL b ) of 5876 ml min À1 kg À1 and was CNS penetrant with a steady-state brain : blood ratio of 0.9 : 1. Following i.p. administration to rats (10 mg kg À1 ), the compound displayed a t 1/2 of 1.4 h with mean brain and blood concentrations (at 1 h after dosing) of 0.80 and 1.0 mM, respectively. 4 SB-656104-A produced a significant reversal of the 5-CT-induced hypothermic effect in guinea pigs, a pharmacodynamic model of 5-HT 7 receptor interaction in vivo (ED 50 2 mg kg À1 ). 5 SB-656104-A, administered to rats at the beginning of the sleep period (CT 0), significantly increased the latency to onset of rapid eye movement (REM) sleep at 30 mg kg À1 i.p. (+93%) and reduced the total amount of REM sleep at 10 and 30 mg kg À1 i.p. with no significant effect on the latency to, or amount of, non-REM sleep. SB-269970-A produced qualitatively similar effects in the same study. 6 In summary, SB-656104-A is a novel 5-HT 7 receptor antagonist which has been utilised in the present study to provide further evidence for a role for 5-HT 7 receptors in the modulation of REM sleep.

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Ghrelin is a 28-amino-acid polypeptide expressed in the stomach and hypothalamus that stimulates GH secretion, increases food intake (FI) and promotes body weight (BW) gain most likely via activation of the growth hormone secretagogue receptor type 1a (GHSR1a). GSK1614343 is a novel selective and potent GHSR antagonist with no partial agonist properties, recently characterized as GH secretion inhibitor by Sabbatini et al. [Chem Med Chem 2010;5:1450–1455]. In the present study, GSK1614343 (10 mg/kg) was not able to antagonize ghrelin-induced food consumption in rat, but unexpectedly stimulated FI and BW gain in both rats and dogs, a profile associated with decreased ghrelin plasma level. Interestingly, GSK1614343 selectively reduced the pro-opiomelanocortin mRNA levels in rat hypothalami chronically treated with the compound. To better understand the observed effects, we administered GSK1614343 (30 mg/kg) to Ghsr null mice and measured body mass components (fat, lean and free fluid) by using a NMR spectrometer. The increases of FI and BW were abolished in Ghsr null mice, while fat and lean masses increased in wild-type mice. Taken together, these results indicate that the orexigenic effect of GSK1614343 is mediated by GHSR1a and that the weight gain could be attributed to the increase of both adiposity and muscle mass, but not to fluid retention. The observed dissociation between effects on GH secretion and effects on FI/BW is inconsistent with a simple hormone-receptor model, suggesting unknown underlying regulations of the ghrelin system whose understanding require further investigation.