A potent nonpeptide antagonist of the substance P (NK1) receptor.

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.

Calcium-independent phosphodiesterase inhibitors as putative antidepressants: [3-(bicycloalkyloxy)-4-methoxyphenyl]-2-imidazolidinones.

The synthesis and biological properties of a novel series of selective calcium-independent phosphodiesterase inhibitors are described. These compounds also inhibit the specific binding of [3H]rolipram to rat brain membranes and exhibit efficacy in preclinical models of antidepressant activity in mice, such as reducing immobility in the forced-swim test and reversing reserpine-induced hypothermia. Imidazolidinones 4 and 16 were found to be the most potent compounds studied.

Nicotinamide ethers: novel inhibitors of calcium-independent phosphodiesterase and [3H]rolipram binding.

The synthesis and biological properties of a series of nicotinamide ethers are described. These compounds, structurally novel calcium-independent phosphodiesterase inhibitors, also inhibit the binding of [3H]rolipram to rat brain membranes and reverse reserpine-induced hypothermia in the mouse. Several compounds exhibited potent in vivo activity comparable to the standard agent, rolipram.

Discriminative stimulus properties of phencyclidine (PCP)-related compounds: correlations with 3H-PCP binding potency measured autoradiographically.

Several PCP analogs, the putative PCP agonist MDP, and the sigma receptor agonists SKF-10,047 and dexoxadrol were tested for their ability to substitute for PCP in animals trained to discriminate PCP from saline. The potencies of these compounds in substituting for PCP in the behavioral task correlated with their abilities to inhibit the specific binding of 3H-PCP to rat hippocampal sections measured autoradiographically, which occurred at a single class of sites with an affinity of 85 nM and a capacity of 2646 fmol/mg protein. In addition to this specific binding, an additional nonspecific but displaceable fraction of total 3H-PCP binding was present. These results suggest that the specific 3H-PCP binding site measured in the hippocampus may be the type of binding site which mediates the behavioral effects of PCP and related compounds. Therefore, measurement of the inhibition of 3H-PCP binding at this site might aid in the search for PCP antagonists.

Experimental evolution of penicillin G acylases from Escherichia coli and Proteus rettgeri.

Proteus rettgeri and Escherichia coli W were shown to express structurally different penicillin G acylases. The enzymes had similar substrate specificity but differed in molecular weight, isoelectric point, and electrophoretic mobility in polyacrylamide gels and did not antigenically cross-react. When the organisms were subjected to environmental conditions which made expression of this enzyme essential for growth, spontaneous mutants were isolated that used different amides as the only source of nitrogen. These mutants acquired the ability to use amides for growth by deregulating the penicillin G acylase and by their evolution to novel substrate specificities. The enzymes expressed by mutants isolated from each genus appeared to have evolved in parallel since each acylase attained similar new substrate specificities when the organisms were subjected to identical selection pressure.

Slow tight-binding inhibition of prolyl endopeptidase by benzyloxycarbonyl-prolyl-prolinal.

Prolyl endopeptidase is a serine proteinase that specifically cleaves peptides on the carboxy side of proline residues. Wilk & Orlowski [(1983) J. Neurochem. 41, 69-75] have shown that benzyloxycarbonyl-prolyl-prolinal (Z-prolyl-prolinal) is a potent inhibitor of prolyl endopeptidase. We show that Z-prolyl-prolinal is a slow-binding inhibitor of mouse brain prolyl endopeptidase with Ki 0.35 +/- 0.05 nM. Kinetic analysis indicates that the mechanism is a simple, but slow, reversible equilibrium between free and bound enzyme (E + I in equilibrium EI) with rate constants for association (kon) and dissociation (koff) of 1.6 X 10(5) M-1.s-1 and approx. 4 X 10(-5) s-1 respectively. Slow-binding inhibition is dependent on the presence of the aldehyde group since the alcohol (Z-prolyl-prolinol) is a rapid and 50,000-fold poorer inhibitor (Ki 19 microM). Prolyl endopeptidase from human brain is also inhibited by Z-prolyl-prolinal with kinetics similar to those of the mouse brain enzyme.