The localization of substance P in brain regions that coordinate stress responses and receive convergent monoaminergic innervation suggested that substance P antagonists might have psychotherapeutic properties. Like clinically used antidepressant and anxiolytic drugs, substance P antagonists suppressed isolation-induced vocalizations in guinea pigs. In a placebo-controlled trial in patients with moderate to severe major depression, robust antidepressant effects of the substance P antagonist MK-869 were consistently observed. In preclinical studies, substance P antagonists did not interact with monoamine systems in the manner seen with established antidepressant drugs. These findings suggest that substance P may play an important role in psychiatric disorders.

Sphingosine 1-phosphate (S1P) is a bioactive lysolipid with pleiotropic functions mediated through a family of G proteincoupled receptors, S1P 1,2,3,4,5 . Physiological effects of S1P receptor agonists include regulation of cardiovascular function and immunosuppression via redistribution of lymphocytes from blood to secondary lymphoid organs. The phosphorylated metabolite of the immunosuppressant agent FTY720 (2-amino-2-(2-[4-octylphenyl]ethyl)-1,3-propanediol) and other phosphonate analogs with differential receptor selectivity were investigated. No significant species differences in compound potency or rank order of activity on receptors cloned from human, murine, and rat sources were observed. All synthetic analogs were high-affinity agonists on S1P 1 , with IC 50 values for ligand binding between 0.3 and 14 nM. The correlation between S1P 1 receptor activation and the ED 50 for lymphocyte reduction was highly significant (p Ͻ 0.001) and lower for the other receptors. In contrast to S1P 1 -mediated effects on lymphocyte recirculation, three lines of evidence link S1P 3 receptor activity with acute toxicity and cardiovascular regulation: compound potency on S1P 3 correlated with toxicity and bradycardia; the shift in potency of phosphorylated-FTY720 for inducing lymphopenia versus bradycardia and hypertension was consistent with affinity for S1P 1 relative to S1P 3 ; and toxicity, bradycardia, and hypertension were absent in S1P 3 Ϫ/Ϫ mice. Blood pressure effects of agonists in anesthetized rats were complex, whereas hypertension was the predominant effect in conscious rats and mice. Immunolocalization of S1P 3 in rodent heart revealed abundant expression on myocytes and perivascular smooth muscle cells consistent with regulation of bradycardia and hypertension, whereas S1P 1 expression was restricted to the vascular endothelium.

OBJECTIVE— Acute activation of G protein–coupled receptor 40 (GPR40) by free fatty acids (FFAs) or synthetic GPR40 agonists enhances insulin secretion. However, it is still a matter of debate whether activation of GPR40 would be beneficial for the treatment of type 2 diabetes, since chronic exposure to FFAs impairs islet function. We sought to evaluate the specific role of GPR40 in islets and its potential as a therapeutic target using compounds that specifically activate GPR40. RESEARCH DESIGN AND METHODS— We developed a series of GPR40-selective small-molecule agonists and studied their acute and chronic effects on glucose-dependent insulin secretion (GDIS) in isolated islets, as well as effects on blood glucose levels during intraperitoneal glucose tolerance tests in wild-type and GPR40 knockout mice (GPR40 −/− ). RESULTS— Small-molecule GPR40 agonists significantly enhanced GDIS in isolated islets and improved glucose tolerance in wild-type mice but not in GPR40 −/− mice. While a 72-h exposure to FFAs in tissue culture significantly impaired GDIS in islets from both wild-type and GPR40 −/− mice, similar exposure to the GPR40 agonist did not impair GDIS in islets from wild-type mice. Furthermore, the GPR40 agonist enhanced insulin secretion in perfused pancreata from neonatal streptozotocin-induced diabetic rats and improved glucose levels in mice with high-fat diet–induced obesity acutely and chronically. CONCLUSIONS— GPR40 does not mediate the chronic toxic effects of FFAs on islet function. Pharmacological activation of GPR40 may potentiate GDIS in humans and be beneficial for overall glucose control in patients with type 2 diabetes.

Structural modifications requiring novel synthetic chemistry were made to the morpholine acetal human neurokinin-1 (hNK-1) receptor antagonist 4, and this resulted in the discovery of 2-(R)-(1-(R)-3, 5-bis(trifluoromethyl)phenylethoxy)-3-(S)-(4-fluoro)phenyl-4-(3-ox o-1 ,2,4-triazol-5-yl)methyl morpholine (17). This modified compound is a potent, long-acting hNK-1 receptor antagonist as evidenced by its ability to displace [125I]Substance P from hNK-1 receptors stably expressed in CHO cells (IC50 = 0.09 +/- 0.06 nM) and by the measurement of the rates of association (k1 = 2.8 +/- 1.1 x 10(8) M-1 min-1) and dissociation (k-1 = 0.0054 +/- 0.003 min-1) of 17 from hNK-1 expressed in Sf9 membranes which yields Kd = 19 +/- 12 pM and a t1/2 for receptor occupancy equal to 154 +/- 75 min. Inflammation in the guinea pig induced by a resiniferatoxin challenge (with NK-1 receptor activation mediating the subsequent increase in vascular permeability) is inhibited in a dose-dependent manner by the oral preadmininstration of 17 (IC50 (1 h) = 0.008 mg/kg; IC90 (24 h) = 1.8 mg/kg), indicating that this compound has good oral bioavailbility and peripheral duration of action. Central hNK-1 receptor stimulation is also inhibited by the systemic preadministration of 17 as shown by its ability to block an NK-1 agonist-induced foot tapping response in gerbils (IC50 (4 h) = 0.04 +/- 0.006 mg/kg; IC50 (24 h) = 0.33 +/- 0.017 mg/kg) and by its antiemetic actions in the ferret against cisplatin challenge. The activity of 17 at extended time points in these preclinical animal models sets it apart from earlier morpholine antagonists (such as 4), and the piperidine antagonists 2 and 3 and could prove to be an advantage in the treatment of chronic disorders related to the actions of Substance P. In part on the basis of these data, 17 has been identified as a potential clinical candidate for the treatment of peripheral pain, migraine, chemotherapy-induced emesis, and various psychiatric disorders.

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