CP-96,345 [(2S, 3S)-cis-2-(diphenylmethyl)-N-[(2-methoxyphenyl)- methyl]-1-azabicyclo[2.2.2]octan-3-amine] is a potent nonpeptide antagonist of the substance P (NK1) receptor. CP-96,345 inhibited 3H-labeled substance P binding and was a classical competitive antagonist in the NK1 monoreceptor dog carotid artery preparation. CP-96,345 inhibited substance P-induced salivation in the rat, a classical in vivo bioassay, but did not inhibit NK2, NK3, or numerous other receptors; it is thus a selective NK1 antagonist. This compound may prove to be a powerful tool for investigation of the physiological properties of substance P and exploration of its role in diseases.

Treatment with the atypical antipsychotics olanzapine and clozapine has been associated with an increased risk for deterioration of glucose homeostasis, leading to hyperglycemia, ketoacidosis, and diabetes, in some cases independent of weight gain. Because these events may be a consequence of their ability to directly alter insulin secretion from pancreatic ␤-cells, we determined the effects of several antipsychotics on cholinergic-and glucose-stimulated insulin secretion from isolated rat islets. At concentrations encompassing therapeutically relevant levels, olanzapine and clozapine reduced insulin secretion stimulated by 10 mol/l carbachol plus 7 mmol/l glucose. This inhibition of insulin secretion was paralleled by significant reductions in carbachol-potentiated inositol phosphate accumulation. In contrast, risperidone or ziprasidone had no adverse effect on cholinergic-induced insulin secretion or inositol phosphate accumulation. None of the compounds tested impaired the islet secretory responses to 8 mmol/l glucose alone. Finally, in vitro binding and functional data show that olanzapine and clozapine (unlike risperidone, ziprasidone, and haloperidol) are potent muscarinic M 3 antagonists. These findings demonstrate that low concentrations of olanzapine and clozapine can markedly and selectively impair cholinergicstimulated insulin secretion by blocking muscarinic M 3 receptors, which could be one of the contributing factors to their higher risk for producing hyperglycemia and diabetes in humans. Diabetes 54:1552-1558, 2005 R ecent reviews of clinical databases have revealed that olanzapine and clozapine carry a higher risk for producing hyperglycemia, ketoacidosis, and new-onset type 2 diabetes than other second-generation antipsychotics (SGAs) or haloperidol, a first-generation antipsychotic (1-6). The use of olanzapine and clozapine is often associated with notable weight gain and dyslipidemia, which are known risk factors in the development of diabetes. However, several reports have described cases of hyperglycemia following olanzapine and clozapine treatment that were not associated with weight gain (7,8). Furthermore, cases exist where switching to other SGAs, such as ziprasidone or risperidone, resulted in the reversal of olanzapine-or clozapine-associated hyperglycemia, suggesting that fundamental differences exist among the SGAs (9 -11).The mechanisms responsible for the increased diabetes risk of olanzapine and clozapine are not known, but in contrast to other SGAs, both compounds are potent muscarinic receptor antagonists (12). This led us to consider the possibility that disruption of the cholinergic processes regulating insulin secretion is one of the underlying mechanisms for impaired glucose regulation. Therefore, we investigated the effects of several antipsychotics on cholinergic-stimulated insulin secretion and the activation of phospholipase C using isolated rat pancreatic islets. Since the cholinergic activation of insulin release is mediated through muscarinic M 3 receptors on ␤-cells ...

No abstract

In pithed dogs pressor responses to phenylephrine were completely inhibited 1 h after phenoxybenzamine 20 mg/kg i.v., but those to norepinephrine were only partially inhibited. The pressor effects of norepinephrine in phenoxybenzamine-treated animals were inhibited by yohimbine, 2.0 mg/kg i.v., but not by prazosin, 0.5 mg/kg i.v. In animals treated with phenoxybenzamine, 20 mg/kg i.v., plus propranolol, 5.0 mg/kg i.v., the partially restored pressor response to epinephrine, and the responses to norepinephrine, were completely inhibited by yohimbine, 2.0 mg/kg i.v., partially inhibited by corynanthine, 5.0 mg/kg i.v., but not affected by prazosin, 0.5 mg/kg i.v. In additional animals treated with phenoxybenzamine plus propranolol, yohimbine, 10, 50, 200 and 500 microgram/kg i.v., caused dose-related inhibition of both the partially restored pressor response to epinephrine, and the pressor responses to norepinephrine. It is concluded that: 1) phenoxybenzamine completely blocks alpha 1, but not alpha 2 vascular receptors; 2) the pressor effect of norepinephrine in phenoxybenzamine-treated animals, and the partially restored pressor effect of epinephrine in phenoxybenzamine-propranolol-treated animals, are both mediated by alpha 2 vascular receptors which are resistant to blockade by phenoxybenzamine.

The effects of substance P, neurokinin A, neurokinin B, [Sar9, Met(O2)11]-substance P, [Nle10]-neurokinin A (4-10) and senktide (succinyl-[Asp6, MePhe8]-substance P (6-11)) on blood pressure and heart rate were studied in anesthetized dogs. Dose-dependent decreases in blood pressure and increases in heart rate were caused by each peptide except senktide. The latter elicited weak hypotensive or hypertensive responses at high doses. The order or potency was as follows: [Sar9, Met(O2)11]-substance P greater than or equal to substance P greater than neurokinin A greater than neurokinin B greater than [Nle10]-neurokinin A (4-10) much greater than senktide. CP-96,345, [(2S,3S)-cis-2-(diphenylmethyl)-N-[(2-methoxyphenyl)-methyl]-1- azabicyclo[2.2.2]octan-3-amine] a selective NK-1 tachykinin receptor blocker, inhibited substance P-induced hypotension in a dose-related manner. Responses to each of the other peptides were inhibited by CP-96,345, 1.0 mg/kg (excluding senktide against which CP-96,345 was not tested). CP-96,344 (1.0 mg/kg i.v.) the 2R-3R enantiomer of CP-96,345 which does not block NK-1 receptors, had no effect on substance P-induced hypotension. We conclude that tachykinin-induced hypotension in dogs is mediated by NK-1 tachykinin receptors.