John Dale Mcdermed

Chapter 1. Biochemical Models for Serotonin Receptors

Publisher Summary This chapter discusses the specificity of ligands used for the characterization of these sites, the distribution of the sites in the brain tissue, the activities of a variety of pharmaca at the sites and correlations with in vitro and in vivo pharmacological activities, some structure–activity relationships, the in vivo regulation of the sites, and their hypothesized involvement in human diseases. The specificity of the ligands and occurrence of the serotonin receptor sites—the enzyme activity of serotonin-stimulated adenylate cyclase—is best detectable in Colliculli of young animals, because the activity is found to decrease rapidly with age. The enzyme was reported to be present in glial cell preparations from horse brain striatumand in a particulate fraction of the central nervous system (CNS) of the snail Helix Pomatia . The S 1 binding sites are labeled with affinity by 3H-serotonin. For specific binding of the 3 H-serotonin, defined by inhibition with 10 μIM unlabelled serotonin assayed at 37 o C, K D -values of 1.4nM14 to 8nM are reported. The labeling of S 2 -receptor binding sites are discussed in this chapter. The binding affinity of drugs for the putative serotonin receptor sites and relationship with pharmacological activity has been explained in the chapter. The S 1 -binding sites and the serotonin-stimulated adenylate dyclase being unrelated a supposed coupling between the two systems was refuted. S 1 -binding data indicates that the sites are to be considered as mere binding sites until further proof for a receptor function is furnished. Correlation between the activities of compounds in biochemical models and in pharmacological models for serotonin receptors S 2 -receptor-binding sites mediate various actions of serotonin and that the binding affinities of serotonin, serotonin-like compounds, and serotonin antagonists are completely compatible with the anticipated features of a serotonin neurotransmitter receptor. A description of the structure–activity relationships at the S 2 -receptor-binding sites and a role for S 2 -receptor alterations in several disease states has been discussed in the chapter.

BW2258U89 : A GRP RECEPTOR ANTAGONIST WHICH INHIBITS SMALL CELL LUNG CANCER GROWTH

The ability of reduced peptide bond analogues of gastrin releasing peptide (GRP) to antagonize small cell lung cancer (SCLC) GRP receptors was investigated. BW462U89, BW1023U90, BW2123U89 and BW2258U89 inhibited binding of (125I-Tyr4) BN to NCI-H345 cells with IC50 values of 5, 6, 140 and 10 nM respectively. The GRP analogues had no effect on basal cytosolic Ca2+ but inhibited the increase caused by 10 nM BN. BW462U89 reversibly blocked the increase in cytosolic Ca2+ caused by BN. The GRP analogues (1 microM) inhibited NCI-H345 colony formation in the absence or presence of 10 nM BN. Also, BW2258U89 (0.4 mg/kg, s.c. daily) inhibited xenograft growth in nude mice. These data indicate that BW2258U89 inhibits SCLC growth in vitro and in vivo.

ENANTIOSELECTIVITY IN THE BINDING OF (+)- AND (−)-2-AMINO-6,7-DIHYDROXY-1,2,3,4-TETRAHYDRONAPHTHALENE AND RELATED AGONISTS TO DOPAMINE RECEPTORS

ABSTRACT The potent DA agonist 5 was resolved into enantiomers. The absolute configurations of the enantiomers of 3 and 5 were determined by chemical degradation. These compounds were tested as inhibitors of 3H-DA binding to membrane fragments from rat striatum. It was found that the configuration of the more potent enantiomer of 5 is opposite to that of 3 and APO. This is relevant to the mode of binding of such agonists to DA receptors.

A novel bombesin receptor antagonist selectively blocks the satiety action of peripherally administered bombesin.

To investigate the effect of a new, specific antagonist for bombesin receptors on the satiating action of exogenous bombesin, adult male rats were adapted to a nondeprivation test regimen with daily access to a palatable liquid food. In a prefeeding paradigm, rats received intraperitoneal injections of the bombesin receptor antagonist, BW2258U89 (6.25, 25, 50, or 100 micrograms kg-1) or vehicle 20 min before, and then a second injection of either bombesin (4 micrograms kg-1), gastrin-releasing peptide (GRP; 16 micrograms kg-1), the C-terminal octapeptide of cholecystokinin (CCK-8; 4 micrograms kg-1), or vehicle 5 min before a 2-h feeding test. BW2258U89 pretreatment antagonized the satiating actions of bombesin and GRP18-27 in a very potent, dose-related manner, but did not antagonize the satiating action of CCK-8. These differential results with BW2258U89 are consistent with prior results showing the potency of this antagonist for bombesin receptor-mediated effects in visceral systems; in addition, they demonstrate the selectivity of the compound for the satiating actions of peripherally administered bombesin and bombesin-like peptides.

BW1023U90: A new GRP receptor antagonist for small-cell lung cancer cells

Abstract Gastrin-releasing peptide (GRP) receptor antagonists were synthesized and their ability to interact with small-cell lung cancer (SCLC) cells determined. [125I]BW1023U90, bound with high affinity (Kd = 2 nM) to a single class of sites (Bmax = 55 fmol/mg protein) using SCLC cell line NCI-H345. [125I]BW1023U90 binding was time dependent and reversible even at 37°C as the ligand was minimally internalized. Specific [125I]BW1023U90 binding was inhibited with high affinity by GRP as well as bombesin (BB) but not neuromedin B (NMB). BW1023U90 inhibited the ability of BB to elevate cytosolic Ca2+ and increase the growth of SCLC cells. A BW1023U90 analogue, BW2258U89 (10 μg/day, SC) slowed SCLC xenograft formation in nude mice and [125I]BW1023U90 localized to SCLC tumors 1 h after injection into nude mice. BW2258U89 (4% by weight) was placed in microspheres and slowly released over a 3-week period in nude mice bearing SCLC xenografts. The microspheres containing BW2258U89 strongly inhibited SCLC growth in vivo. A radioimmunoassay was developed for the GRP receptor antagonists and the rabbit antiserum cross-reacted totally with BW2258U89 or BW1023U90. BW2258U89 immunoreactivity (5 nM) was detected in the plasma of nude mice containing the microspheres after 1 week. These data suggest that GRP receptor antagonists bind to receptors on SCLC tumors.

Synthesis of the carbonic acid benzotriazol-1-yl-ester-(2-biotinylamino)-9h-fluoren-9-ylmethyl ester: A convenient transient-biotinylation reagent for use in affinity chromatography

Abstract Stepwise synthesis of hydrophobic peptides frequently yields deletion products, which often require extensive purification and identification. We synthesized a new transient-biotinylation reagent 9 , which was conveniently used in affinity Chromatography of crude products ( exemplified by 11-I and 11-II ), to afford pure peptides ( 15-I and 15-II , respectively). Unlike conventional affinity Chromatography, reagent 9 leads to free N-terminal peptides, which are thus amenable to further chemical manipulations.

Chapter 2. Antipsychotic Agents and Dopamine Agonists

Publisher Summary This chapter summarizes the effective results of neuroleptic (antipsychotic) drugs in symptomatic treatment of schizophrenia, whose etiologies are unknown and may not be identical. This review begins with the recent discoveries about dopamine (DA) receptors. From the identification of DA receptors at the biochemical level, it has become clear that heterogeneity of DA receptors exists. Kainic acid injection into the striatum destroys striatal neurons, on which postsynaptic DA receptors are located while sparing axons that pass through this region and terminals that end within it. The bovine parathyroid gland is a tissue with a relatively homogeneous population of D-1 (cyclase-linked) receptors. In this tissue, DA stimulates the accumulation of cyclic adenosine monophosphate (c-AMP) and this event is followed by the release of parathyroid hormone from the gland. Apomorphine (APO) acts as a pure antagonist in this system. It appears that haloperidol and the other classical neuroleptics block both types of DA receptors. It is a corollary of the DA hypothesis of schizophrenia that pharmacological screening methods for antipsychotics are usually designed to discover DA blocking agents. Neuroleptics typically increase DA turnover, elevate prolactin levels, compete with DA receptor ligands for membrane binding sites, induce catalepsy, and block conditioned avoidance responding (CAR) in trained animals. Amoxapine that was previously known as a clinically effective antidepressant has now been shown by a Lederle group to have significant neuroleptic activity in a number of animal models. Nomifensin is an antidepressant that produces significant DA-mimetic motor effects in animal models. The ergot alkaloids have generally complex pharmacological profiles, but some with DA agonist properties are therapeutically useful.

Chapter 6. Analgesics, Opioids, and Opioid Receptors

Publisher Summary The search for superior analgesics with improved side-effect profiles continues in the clinic through additional evaluations of nonsteroidal anti-inflammatory peripheral analgesics and through continued study of oral administration of centrally acting analgesics. Non-steroidal anti-inflammatory drugs (NSAIDs) evaluated as oral analgesics for postoperative pain includes: fenoprofen, etodolac, isoxepac, zomepirac, and diflunisal. For relief of pain following outpatient surgery, oral fenoprofen (200 mg) compares favorably with parenteral morphine (8 mg) after an initial two hour period during that morphine is more effective. Diflunisal (dolobid) appears to be a well-tolerated NSAID. Diflunisal is an efficacious and long-acting (up to 12 hours) analgesic for oral surgery patients and is effective against pain encountered in general practice. In the treatment of chronic back pain, diflunisal (500 mg twice daily) appears superior to paracetamol (1000 mg four times a day) although less effective than naproxen sodium (550 mg twice a day). Studies with diflunisal, flurbiprofen, ibuprofen, naproxen sodium, and zomepirac sodium provide additional evidence of the effectiveness of oral NSAIDs for the treatment of the symptoms of primary dysmenorrhea. In the treatment of renal colic, intramuscular injection of the NSAID diclofenac (50 mg) is more effective than the injection of a narcotic–spasmolytic combination drug.

Stereochemistry of Dopamine Receptor Agonists

In order to help understand the mode of binding of dopamine agonists to their receptors, four agonists of the 2-aminotetralin series were resolved into (+)- and (−)-enantiomers, their absolute configurations were determined, and their receptor affinities were evaluated in binding assays. The most important result seen was an inversion of stereochemical requirement which is governed by the location of hydroxyl groups in the aromatic ring. Thus, 5- and 5,6-dihydroxyl compounds require the 2S configuration while 7- and 6,7-dihydroxyl compounds must be 2R. This implies a specific orientation of such ligands to the receptor, for which a model is proposed.

A Convenient Synthesis of the Orthogonally-Protected Benzodiazepine-2,5-Dione Scaffold

Abstract We have identified the benzodiazepine-2,5-dione 4 as a convenient, orthogonally-protected template, suitable for parallel solid-phase chemistry. Scaffold 4 offers superior stability, compared to other, analogous benzodiazepine-2,5-diones, such as A. We describe a gram-scale synthesis of 4 in six steps and in 25% yield.