[<Superscript>3</Superscript>H]LY334370, a novel radioligand for the 5-HT<Subscript>1F</Subscript> receptor. II. Autoradiographic localization in rat,guinea pig,monkey and human brain

LY334370 is a high affinity, selective agonist at the 5-HT_1F receptor. On this basis, the tritiated compound was examined for its utility in autoradiography to localize the 5-HT_1F receptor in rat and guinea pig brain regions. Specific 5-HT_1F receptor binding in rat brain was found in layers 4–5 of all cortical regions examined, as well as olfactory bulb and tubercle, nucleus accumbens, caudate putamen, parafascicular nucleus of the thalamus, medial mammillary nucleus, the CA3 region of the hippocampus, subiculum, and several amygdaloid nuclei. In guinea pig brain, the [³H]LY334370 binding sites were found at highest density in claustrum, but also in a layer of the cortex, caudate putamen, nucleus accumbens, thalamus, and medial mammillary nucleus. Some species differences in the distribution of the 5-HT_1F receptor were noted. Side by side comparison of rat brain autoradiography with [³H]LY334370 and [³H]sumatriptan showed labeling in the same brain regions. Preliminary binding studies in rhesus monkey and human brain sections showed [³H]LY334370 binding in cortical layers 4–5, subiculum (in the monkey), and the granule cell layer of the cerebellum. These findings suggest a discrete localization of the 5-HT_1F receptor in the rat, guinea pig, monkey and human brain, and confirms the utility of [³H]LY334370 as a potential tool to explore further the localization and possible functions of the 5-HT_1F receptor.     

Absolute configurations and pharmacological activities of the optical isomers of fluoxetine, a selective serotonin-uptake inhibitor

Fluoxetine is a potent and selective inhibitor of the neuronal serotonin-uptake carrier and is a clinically effective antidepressant. Although fluoxetine is used therapeutically as the racemate, there appears to be a small but demonstrable stereospecificity associated with its interactions with the serotonin-uptake carrier. The goals of this study were to determine the absolute configurations of the enantiomers of fluoxetine and to examine whether the actions of fluoxetine in behavioral tests were enantiospecific. (S)-Fluoxetine was synthesized from (S)-(-)-3-chloro-1-phenylpropanol by sequential reaction with sodium iodide, methylamine, sodium hydride, and 4-fluorobenzotrifluoride. (S)-Fluoxetine is dextrorotatory (+1.60) in methanol, but is levorotatory (-10.85) in water. Fluoxetine enantiomers were derivatized with (R)-1-(1-naphthyl)ethyl isocyanate, and the resulting ureas were assayed by 1H NMR or HPLC to determine optical purities of the fluoxetine samples. Both enantiomers antagonized writhing in mice; following sc administration of (R)- and (S)-fluoxetine, ED50 values were 15.3 and 25.7 mg/kg, respectively. Moreover, both enantiomers potentiated a subthreshold analgesic dose (0.25 mg/kg) of morphine, and ED50 values were 3.6 and 5.7 mg/kg, respectively. Following ip administration to mice, the two stereoisomers antagonized p-chloroamphetamine-induced depletion of whole brain serotonin concentrations. ED50 values for (S)- and (R)-fluoxetine were 1.2 and 2.1 mg/kg, respectively. The two enantiomers decreased palatability-induced ingestion following ip administration to rats; (R)- and (S)-fluoxetine reduced saccharin-induced drinking with ED50 values of 6.1 and 4.9 mg/kg, respectively. Thus, in all biochemical and pharmacological studies to date, the eudismic ratio for the fluoxetine enantiomers is near unity.     

THA After Acetabular Fracture Fixation: Is Frozen Section Necessary?

Background  

Infection is uncommon after THA performed for failed acetabular fracture repair, despite a high reported incidence of culture-positive fixation implants. The use of frozen section analysis at the time of THA after acetabular fracture fixation surgery is unknown.     

Dihydropyridazinone cardiotonics: the discovery and inotropic activity of 1,3-dihydro-3,3-dimethyl-5-(1,4,5,6-tetrahydro-6-oxo-3-pyridazinyl)-2H -indol-2- one

We discovered that 6 (N-[4-(1,4,5,6-tetrahydro-6-oxo-3-pyridazinyl)phenyl]acetamide) is a potent positive inotrope in dogs, and we have prepared several lactam analogues of this agent. These included 16 (1,3-dihydro-5-(1,4,5,6-tetrahydro-6-oxo-3-pyridazinyl)-2H-indol-2-one), 32 (the analogous quinolin-2-one), and 37 (the analogous benzazepin-2-one). The inotropic ED50's of these compounds were 24, 3.3, and 5.2 micrograms/kg, respectively, after iv administration to pentobarbital-anesthetized dogs. Compound 20 (LY195115, 1,3-dihydro-3,3-dimethyl-5-(1,4,5,6-tetrahydro-6-oxo-3-pyridazinyl)-2H-i ndol-2- one), the geminal dimethyl analogue of 16, was 3.5-fold more potent than 16 when administered iv (ED50 = 6.8 micrograms/kg). However, the most profound effect of the geminal alkyl substitution was on oral activity. The approximate ED50's of 20 and 16 after oral administration to conscious dogs were 25 and 400 micrograms/kg, respectively. The increase in contractility produced by 25 micrograms/kg of 20 was maximally sustained in excess of 8 h. Thus, 20 is one of the most potent and long-acting oral inotropes described to date.     

Esophageal injury from thoracic pedicle screw placement in a polytrauma patient: a case report and literature review

The authors present a case report illustrating a visceral complication that may occur as result of thoracic pedicle screw placement. The case describes the previously unreported occurrence of esophageal impingement secondary to anterior vertebral body perforation by a pedicle screw at the third thoracic vertebra. This case highlights the challenge of thoracic pedicle screw placement and the importance of preoperatively measuring the maximum anterior-posterior dimension of the vertebral body.     

Radiolabeling of a high potency cannabinoid subtype‐1 receptor ligand,N‐(4‐fluoro‐benzyl)‐4‐(3‐(piperidin‐1‐yl)‐indole‐1‐sulfonyl)benzamide (PipISB), with carbon‐11 or fluorine‐18

PipISB [N‐(4‐fluoro‐benzyl)‐4‐(3‐(piperidin‐1‐yl)‐indole‐1‐sulfonyl)benzamide, 9] was identified as a selective high potency CB₁ receptor ligand. Here we describe the labeling of 9 with positron‐emitters to provide candidate radioligands for imaging brain CB₁ receptors with positron emission tomography (PET). The radiolabeling of 9 was achieved by two methods, method A with carbon‐11 and method B with fluorine‐18. In method A, [¹¹C]9 was prepared in one step from [¹¹C]carbon monoxide, itself prepared from cyclotron‐produced [¹¹C]carbon dioxide. In method B, [¹⁸F]9 was prepared from cyclotron‐produced [¹⁸F]fluoride ion in a two‐stage, four‐step synthesis with [¹⁸F]4‐fluoro‐benzyl bromide as a labeling agent. The radiosynthesis time for method A was 44 min; decay‐corrected radiochemical yields (RCYs) from [¹¹C]carbon monoxide ranged from 3.1 to 11.6% and specific radioactivities ranged from 21 to 67 GBq/µmol. The radiosynthesis time for method B was 115 min; RCYs from [¹⁸F]fluoride ion ranged from 1.5 to 5.6% and specific radioactivities ranged from 200 to 348 GBq/µmol. With these methods, [¹¹C]9 and [¹⁸F]9 may be prepared in adequate activity and quality for future evaluation as PET radioligands. Copyright © 2008 John Wiley & Sons, Ltd.     

Imidazole-pyridine bioisosterism: comparison of the inotropic activities of pyridine- and imidazole-substituted 6-phenyldihydropyridazinone cardiotonics

We previously reported the structure-activity relationships (SAR), molecular structure, pharmacology, and molecular pharmacology of indolidan (LY195115), a potent and long-acting dihydropyridazinone cardiotonic. Our 6-phenyldihydropyridazinone SAR studies revealed the critical nature of the substituent at the para position of the phenyl ring. An acetamido substituent provided potent cardiotonic activity and we hypothesized that this may relate to the ability of the acetamide carbonyl to function as a hydrogen-bond acceptor. To further address this question, we prepared 15 (4,5-dihydro-6-[4-(3-pyridinyl)phenyl]-3(2H)-pyridazinone), the 3-pyridyl analogue of imazodan. As is the case with imazodan, this (pyridylphenyl)dihydropyridazinone possesses a nitrogen three atoms removed from the phenyl ring, but the molecular framework through which it is attached to the phenyldihydropyridazinone moiety is altered. After iv administration to pentobarbital-anesthetized dogs, inotropic ED50 values of 15, imazodan, and the parent compound, 4,5-dihydro-6-phenyl-3(2H)-pyridazinone, were 19.4, 50.1, and 6330 micrograms/kg, respectively. Thus, 15 is over 2-fold more potent than imazodan and 326-fold more potent than the parent, unsubstituted compound. These data, as well as data obtained with other congeners, are consistent with the hypothesis that a suitably oriented hydrogen-bond-acceptor site contributes to the high degree of inotropic potency observed with these dihydropyridazinone cardiotonics.     

Structure-activity relationships of (arylalkyl)imidazole anticonvulsants: comparison of the (fluorenylalkyl)imidazoles with nafimidone and denzimol

A recently discovered and structurally distinct class of antiepileptic drugs is the (arylalkyl)imidazoles. Two independently discovered representatives of this class, denzimol (alpha-[4-(2-phenylethyl)phenyl]-1H-imidazole-1-ethanol) and nafimidone (2-(1H-imidazol-1-yl)-1-(2-naphthalenyl)ethanone), are undergoing clinical evaluation. Our structure-activity relationship (SAR) studies revealed that in addition to the naphthalenyl and phenethylphenyl aryl moieties of nafimidone and denzimol, respectively, fluorenyl, benzo[b]thienyl, and benzofuranyl aryl groups provided several highly active (arylalkyl)imidazole anticonvulsants. These structurally diverse aryl moieties, and comparable anticonvulsant activities, lend credence to the hypothesis that the pharmacophore of this class of anticonvulsants is the alkylimidazole portion of the molecule, with the lipophilic aryl portion enabling penetration of the blood-brain barrier. We focused our SAR studies on the (fluorenylalkyl)imidazole series. A representative compound from this series is 1-(9H-fluoren-2-yl)-2-(1H-imidazol-1-yl)ethanone. This agent was twice as potent as nafimidone in inhibiting maximal electroshock seizures in mice (po ED50's = 25 and 56 mg/kg, respectively) and considerably less toxic in the rat (po LD50's = 4550 and 504 mg/kg, respectively). The tertiary alcohol alpha-(9H-fluoren-2-yl)-alpha-methyl-1H-imidazole-1-ethanol was as potent as denzimol in mice (po ED50's = 10 and 12 mg/kg, respectively). This series of imidazole anticonvulsants was highly selective; while many compounds displayed potent antielectroshock activity, little or not activity was observed against pentylenetetrazole-induced clonic seizures or in the horizontal screen test for ataxia. All active compounds that we tested in this series, as well as denzimol and nafimidone, potentiated hexobarbital-induced sleeping time in mice, probably by imidazole-mediated inhibition of cytochrome P-450. The SAR's for the anticonvulsant activity and the sleeping time potentiation were similar. The propensity of these (arylalkyl)imidazole anticonvulsants to interact strongly with cytochrome P-450 and thereby impair the metabolism of other antiepileptic drugs may severely limit their clinical utility as anticonvulsants.     

Distal biceps tendon rupture: biomechanical analysis of repair strength of the Bio-Tenodesis screw versus suture anchors

The purpose of this study was to compare the strength and stiffness of distal biceps tendon ruptures repaired with either a Bio-Tenodesis screw or suture anchor technique in a cadaveric model. Ten matched pairs of cadaveric arms underwent simulated distal biceps tendon ruptures and were repaired with either a Bio-Tenodesis screw or suture anchor technique. We analyzed pullout strength, stiffness, and mode of failure for each construct. The mean pullout strength of the repair with a Bio-Tenodesis screw was significantly higher (192 N [SD, 42.5 N] vs 147 N [SD, 29.5 N], P < .013). Use of the Bio-Tenodesis screw is an effective means of repairing distal biceps tendon ruptures. It provides significantly more initial pullout strength compared with suture anchors. This could potentially allow more aggressive rehabilitation and faster return to function.