New CCK2 agonists confirming the heterogeneity of CCK2 receptors: characterisation of BBL454.

Pharmacological studies were undertaken with a new series of cholecystokinin(2) CCK(2) agonists in order to assign to them a CCK(2A) or CCK(2B) pharmacological profile. The open-field test was chosen as the discrimination test of CCK(2B) agonists. The most interesting agonist, BBL454 (0.03-300 microg/kg) induced hyperactivity which was blocked by a CCK(2) antagonist, the D1 antagonist SCH23390, the delta-opioid antagonist naltrindole, but not a CCK(1) antagonist. All compounds active in the open-field test are characterised by a common structural feature, -COCH(2)CO-Trp-NMeNle-Asp-Phe-NH(2), whereas inactive compounds do not possess such a motive. Therefore, this feature can be considered crucial for CCK(2B) activity. BBL454 (0.03-3 microg/kg) improved memory in a two-trial memory test while it was very weakly active on the peripheral CCK(2) receptor, and did not evoke anxiogenic effects in the plus-maze test. The synthesis of BBL454 is simple, its minimal active dose is 30 ng/kg and no "bell-shaped" responses were observed. These results suggest that BBL454 could be considered to be the new CCK(2B) reference agonist.

Alpha-lactalbumin-enriched diets enhance serotonin release and induce anxiolytic and rewarding effects in the rat.

Among food proteins, alpha-lactalbumin (LAC) has the highest ratio of tryptophan (Trp) over its competitor amino acids. Consequently, contrary to casein (CAS), LAC ingestion increases Trp access to the brain leading to enhanced serotonin (5-HT) synthesis. As an index of serotonergic activity, we assessed extracellular 5-HT in response to LAC ingestion, using microdialysis, and performed behavioural tests in rats in order to characterise the suggested improvements of mood observed in humans after ingestion of this protein. Rats were fed with diets enriched either in LAC or CAS as control, acutely (30 min meals) or chronically (3 and 6 days). A 30 min LAC meal significantly increased 5-HT release in the medial hypothalamus. This effect disappeared after 3 and 6 days of diet. The basal premeal 5-HT levels were increasingly enhanced by the LAC diet. Compared to a CAS meal, LAC increased the percentage of time spent on the open arms of the elevated plus maze and the number of visits to the centre of the open field, suggesting an anxiolytic-like effect. A single LAC meal decreased sucrose consumption, while 3 or 6 days diets enhanced it, reflecting an appetitive and/or rewarding action. In conclusion, LAC ingestion induces anxiolytic-like and rewarding effects possibly related to serotonergic activation. Shifting transiently, the commonly consumed CAS-enriched to LAC-enriched diets may induce beneficial effects on mood.

N-[2-(Indan-1-yl)-3-mercapto-propionyl] amino acids as highly potent inhibitors of the three vasopeptidases (NEP, ACE, ECE): In vitro and In vivo activities.

We have previously reported the design of a lead compound 1a for the joint inhibition of neprilysin (NEP, EC 3.4.24.11), angiotensin converting enzyme (ACE, EC 3.4.15.1) and endothelin converting enzyme (ECE-1, EC 3.4.24.71), three metallopeptidases which are implicated in the regulation of fluid homeostasis and vascular tone. We report here the synthesis and biological activities of analogues derived from this lead with inhibitory potencies in the nanomolar range for the three enzymes. Compounds 8b and 15c are the most potent triple inhibitors described to date.

Deletion of CCK2 receptor in mice results in an upregulation of the endogenous opioid system.

Stimulation of the brain CCK2 receptor by the C-terminal octapeptide CCK8 of cholecystokinin (CCK) negatively modulates opioid responses. This suggests the existence of physiologically relevant interactions between endogenous CCK and opioid peptides, opening new perspectives particularly in the treatment of pain or drug addiction. CCK2 receptor-deficient mice were used to analyze the incidence of this gene invalidation on opioid system. Compared with wild-type mice, mutants exhibited the following: (1) a hypersensitivity to the locomotor activity induced by inhibitors of enkephalin catabolism or by morphine; (2) a spontaneous hyperalgesia to thermal nociceptive stimulus, which was reversed by previous administration of the NMDA antagonist MK-801 [(+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine maleate], and a large reduction in analgesic effects of endogenous or exogenous opioids; and (3) a more severe withdrawal syndrome after chronic morphine treatment. As expected, stimulation of mu, delta, and D2 receptors on brain tissue of wild-type animals induced a dose-dependent decrease in adenylate cyclase activity, whereas a striking mirror effect was observed in mutants. All of these results suggest that the absence, in knock-out mice, of the negative feedback control on the opioid system, normally performed out by CCK2 receptor stimulation, results in an upregulation of this system. These biochemical and pharmacological results demonstrate the critical role played by CCK2 receptors in opioid-dependent responses.

Inhibición mixta de la endopeptidasa neutra y de la enzima convertidora por el compuesto S21402 (RB105) en un modelo experimental de infarto de miocardio / Inhibition of both angiotensin converting enzyme and neutral endopeptidase by S21402 in rats with experimental myocardial infarction

El vaso constrictor, angiotensina II y el péptido natriurético auricular (PNA) tienen funciones opuestas en el desarrollo de la insuficiencia cardíaca congestiva realizada en un modelo de insuficiencia cardíaca (ICC) en ratas. Este modelo de insuficiencia cardíaaca se caracteriza por una retención de sal a pesar del aumento de la concentración plasmática de PNA, indicando la ausencia de respuestas renales al PNA. S21402 (RB105), N-2S, 3R-(2-mercaptomethyl-1-oxo-3-phenyl butyl)L-alanine]}, es un inhibidor mixto que inhibe la enzima convertidora de angiotensina (ECA; Ki=4,2ñ0,5nM) y la endopeptidasa neutra (NEP;Ki=1,7ñ0,3nM). La inhibición de la NEP potencializa el PNA endógeno, y la inhibición de la ECA bloquea la producción de angiotensina II. La inhibición de las dos peptidasas permite una potencialización más completa de la bradicinina (BK). La inducción de la insuficiencia cardíaca en ratas por ligadura de las coronarias produjo el aumento de las concentraciones plasmáticas basales de PNA, de cGMP y de la renina, las cuales están relacionadas con el tamaño del infarto (moderados y severos). El PNA, el cGMP y la BK urinarias aumentan en las ratas con ICC en relación al tamaño del infarto. El S21402 (RB105) (25 mg.kg-1 i.v.) indujo un descenso de la presión arterial y un aumento de la natriuresis en función de la severidad del infarto. El compuesto S21402 (RB105) indujo un aumento de la renina plasmática a pesar del nivel basal elevado de la renina en los animales con ICC. El inhibidor mixto no produjo aumento detectable del PNA plasmático. Sin embargo, el cGMP plasmático fue aumentado por el compuesto S21402 (RB105) en función de la severidad del infarto. Las excreciones urinarias del PNA, del cGMP y de la BK fueron también aumentadas por el inhibidor mixto en función de la severidad del infarto. Independientemente del tamaño del infarto, el S21402 (RB105) es capaz de inducir natriuresis en un modelo caracterizado por la desensibilidad a la acción del PNA. La inhibición de ambas peptidasas (MEP,ECA) bloquea también la producción de angiotensina II. Esta combinación de efectos renales y vasculares podría tener un interés terapéutico de la insuficiencia cardíaca congestiva