Total body skeletal muscle mass estimated by magnetic resonance imaging and creatine (methyl-d3 ) dilution in athletes

Creatine dilution (D₃ -cr) is a technique for estimating total skeletal muscle mass (SMM) with practical utility, but has not been applied in athletic populations where body composition may differ to that in the normal population. This study aimed to assess the agreement between SMM derived from both D₃ -cr and that obtained from whole-body magnetic resonance imaging (MRI) in 15 male and 5 female national level kayakers (stature: 182.0 ± 13.1 and 170.0 ± 9.0 cm; body mass: 80.6 ± 9.9 and 66.4 ± 6.0 kg; V̇O₂ peak: 56.5 ± 7.0 and 49.6 ± 4.4 mL kg^-1  min^-1 , mean ± SD). SMM was determined following 60 mg of dosed D₃ -cr and analysis of expelled urine collected on four subsequent days for creatine, creatinine, D₃ -cr, and D₃ -creatinine using liquid chromatography/mass spectroscopy. SMM was then estimated by assuming a creatine pool size of 4.3 g/kg. During the same time period, a whole-body MRI was undertaken to derive SMM from the analysis of multiple slices taken across the body. A strong positive correlation (F = 74.32; R = 0.90; P < .0001) between the two methods was observed, but the D₃ -cr SMM was found to be significantly higher (43.3 ± 6.8 kg) when compared with MRI (36.3 ± 5.8 kg, P < .0001). However, the difference between the methods was removed when a higher intramuscular creatine pool (5.1 g/kg) was assumed. These data show that D₃ -cr has potential utility in athletes, as referenced against MRI, but show that assumptions regarding creatine pool size need to be carefully considered.

Manometric evaluation of the motilin receptor agonist camicinal (GSK962040) in humans

BACKGROUND

The gut hormone motilin stimulates gastrointestinal motility by inducing gastric phase III of the migrating motor complex (MMC) and enhancing the rate of gastric emptying. Camicinal (GSK962040), a small molecule motilin receptor agonist, has been shown to increase gastrointestinal motility.

METHODS

In this proof of concept study the effects of camicinal on MMC activity, esophageal and gastric pH was evaluated in eight healthy volunteers as a secondary endpoint. Doses of 50 and 150 mg were compared to placebo for a period of 24 hours in a double-blinded randomized crossover trial.

KEY RESULTS

The 50 mg dose (n=4) of camicinal had no significant impact on gastroduodenal manometry or pH parameters. A single dose of 150 mg (n=4) induced a gastric phase III after 0:34 h (0:25-0:58), which was significantly faster compared to placebo (18:15 h (4:32-22:16); P=.03). Moreover, the high dose significantly increased the occurrence of gastric phase III contractions compared to placebo (12% vs 39%; P=.0003). This increase in gastric phase III contractions during a period of 24 hour was due to an increased occurrence of gastric phases III during the daytime (5% vs 50%; P=.0001). The same dose however did not affect small bowel manometry parameters or esophageal and gastric pH.

CONCLUSIONS AND INFERENCES

Considering its stimulating effect on the MMC and gastric emptying, camicinal is an attractive candidate for the treatment of gastroparesis and gastroesophageal reflux disease. This trial was registered at clinicaltrials.gov as NCT00562848.

A randomized, double-blind, placebo-controlled trial of camicinal in Parkinson's disease

Background: Delayed gastric emptying may impair l‐dopa absorption, contributing to motor fluctuations. We evaluated the effect of camicinal (GSK962040), a gastroprokinetic, on the absorption of l‐dopa and symptoms of PD.

Methods: Phase II, double‐blind, placebo‐controlled trial. Participants were randomized to receive camicinal 50 mg once‐daily (n = 38) or placebo (n = 20) for 7 to 9 days.

Results:l‐dopa exposure was similar with coadministration of camicinal compared to placebo. Median time to maximum l‐dopa concentration was reduced, indicating more rapid absorption of l‐dopa. Camicinal resulted in significant reduction in OFF time (–2.31 hours; 95% confidence interval: –3.71, –0.90), significant increase in ON time (+1.88 hours; 95% confidence interval: 0.28, 3.48) per day, and significant decrease in mean total MDS‐UPDRS score (–12.5; 95% confidence interval: –19.67, ‐5.29). Camicinal treatment was generally well tolerated.

Conclusions: PD symptom improvement with camicinal occurred in parallel with more rapid absorption of l‐dopa. This study provides evidence of an improvement of the motor response to l‐dopa in people with PD treated with camicinal 50 mg once‐daily compared with placebo, which will require further evaluation. © 2017 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

The effect of camicinal (GSK962040), a motilin agonist, on gastric emptying and glucose absorption in feed-intolerant critically ill patients: a randomized, blinded, placebo-controlled, clinical trial

Background

The promotility agents currently available to treat gastroparesis and feed intolerance in the critically ill are limited by adverse effects. The aim of this study was to assess the pharmacodynamic effects and pharmacokinetics of single doses of the novel gastric promotility agent motilin agonist camicinal (GSK962040) in critically ill feed-intolerant patients.

Methods

A prospective, randomized, double-blind, parallel-group, placebo-controlled, study was performed in mechanically ventilated feed-intolerant patients [median age 55 (19–84), 73 % male, APACHE II score 18 (5–37) with a gastric residual volume ≥200 mL]. Gastric emptying and glucose absorption were measured both pre- and post-treatment after intragastric administration of 50 mg (n = 15) camicinal and placebo (n = 8) using the ¹³C-octanoic acid breath test (BTt_1/2), acetaminophen concentrations, and 3-O-methyl glucose concentrations respectively.

Results

Following 50 mg enteral camicinal, there was a trend to accelerated gastric emptying [adjusted geometric means: pre-treatment BTt_1/2 117 minutes vs. post- treatment 76 minutes; 95 % confidence intervals (CI; 0.39, 1.08) and increased glucose absorption (AUC_240min pre-treatment: 28.63 mmol.min/L vs. post-treatment: 71.63 mmol.min/L; 95 % CI (1.68, 3.72)]. When two patients who did not have detectable plasma concentrations of camicinal were excluded from analysis, camicinal accelerated gastric emptying (adjusted geometric means: pre-treatment BTt_1/2 121 minutes vs. post-treatment 65 minutes 95 % CI (0.32, 0.91) and increased glucose absorption (AUC_240min pre-treatment: 33.04 mmol.min/L vs. post-treatment: 74.59 mmol.min/L; 95 % CI (1.478, 3.449). In those patients receiving placebo gastric emptying was similar pre- and post-treatment.

Conclusions

When absorbed, a single enteral dose of camicinal (50 mg) accelerates gastric emptying and increases glucose absorption in feed-intolerant critically ill patients.

Trial registration

The study protocol was registered with the US NIH clinicaltrials.gov on 23 December 2009 (Identifier NCT01039805).

The pharmacodynamics, safety and pharmacokinetics of single doses of the motilin agonist, camicinal, in type 1 diabetes mellitus with slow gastric emptying

BACKGROUND AND PURPOSE

Here we have investigated the pharmacokinetics, pharmacodynamics and safety of single doses of camicinal in type 1 diabetes mellitus (T1DM) patients with a history of slow gastric emptying with symptoms consistent with gastroparesis.

EXPERIMENTAL APPROACH

In a randomized, double-blind, placebo-controlled, incomplete block, three-period, two-centre crossover study, patients received oral administration of placebo and two of the three possible doses of camicinal (25, 50 or 125 mg). Gastric emptying ((13) C-octanoic acid breath test), pharmacokinetics and safety were primary outcomes.

KEY RESULTS

Nine of the 10 patients enrolled completed the study. Gastric half-emptying time decreased by -95 min (95% CI: -156.8, -34.2) after a single dose of camicinal 125 mg compared with placebo (52 vs. 147 min, P < 0.05), representing a 65% improvement. A decrease of the gastric half-emptying time compared with placebo (approximately 39 min) was observed with camicinal 25 and 50 mg, representing a 27% reduction for both doses (not statistically significant). A positive exposure-response relationship was demonstrated across all doses. The effects of camicinal on gastric half-emptying time were not influenced by fasting glucose levels. Single doses up to 125 mg were well tolerated. Camicinal was well absorbed, exhibiting linear and approximately dose-proportional pharmacokinetic characteristics and a clear exposure-response relationship with gastric emptying.

CONCLUSIONS AND IMPLICATIONS

Camicinal significantly accelerated gastric emptying of solids in T1DM patients following administration of a single oral dose. Camicinal was well tolerated and exhibited similar pharmacokinetic characteristics in diabetic patients to those previously reported in healthy volunteers.

Relative Bioavailability of a Single Dose of Belimumab Administered Subcutaneously by Prefilled Syringe or Autoinjector in Healthy Subjects

Intravenous belimumab is approved for the treatment of systemic lupus erythematosus; subcutaneous self‐administration would enable greater patient access. This study assessed relative bioavailability, tolerability, and safety of 1 subcutaneous dose of self‐administered belimumab by healthy subjects using a single‐use autoinjector or prefilled syringe. Subjects (randomized 1:1:1:1) self‐administered belimumab 200 mg subcutaneously (abdomen or thigh) by prefilled syringe or autoinjector. Pharmacokinetics, adverse events (AEs), injection‐site pain, and administration errors were recorded. Of 81 subjects, 5 experienced administration errors and were excluded from pharmacokinetic analyses. Mean serum belimumab concentration profiles were similar for both devices, with a weak trend toward higher concentrations for thigh injection compared with abdominal injections. Maximum observed serum concentration was slightly higher with the autoinjector (27.0 vs 25.3 µg/mL) and area under the concentration–time curve slightly lower (701 vs 735 day · μg/mL), compared with the prefilled syringe. Incidence of AEs was 51% (41 of 81 subjects; headache was most common), with no serious or severe AEs. Median injection‐site pain scores were low (0 after 1 hour). Device handling was reported as acceptable by ≥95% of autoinjector users and ≥90% of prefilled syringe users for each characteristic assessed. These results support the use of either device for belimumab subcutaneous administration.

The effects of camicinal, a novel motilin agonist, on gastro-esophageal function in healthy humans-a randomized placebo controlled trial

BACKGROUND

A proportion of patients with foregut dysmotility fail to respond to standard interventions. Motilin agonists may be beneficial in this group. We aimed to determine the effect of camicinal, a novel motilin agonist, on gastrointestinal physiology in healthy volunteers.

METHODS

Healthy male subjects were randomly assigned to receive a single dose of 125 mg camicinal or placebo in a double-blind cross-over design. Esophageal function and reflux indices were assessed using high-resolution manometry (pre and 1.5-h post dose) and 24-h ambulatory multichannel intraluminal impedance/pH. After a standardized meal, subjects ingested a wireless motility capsule from which compartmental transit times and motility indices were derived. Subjects were restudied with the alternate intervention after 7 days.

KEY RESULTS

The study subjects (12 male, mean age 47.4 years, range 22-55) tolerated the drug well, except one who exhibited mild abdominal pain on both placebo and camicinal. In comparison to placebo, gastric emptying time (GET) was accelerated following camicinal (-115.4 min, 95% confidence interval -194.4, -36.4, p = 0.009). No effect was demonstrable on esophageal function, small bowel, colonic, or whole bowel transit times and motility indices. With camicinal, as part of a post hoc analysis, there was a trend association between the percentage reduction in GET and total number of acidic reflux events (r = 0.56, p = 0.09).

CONCLUSIONS & INFERENCES

Camicinal decreases GET and was generally well-tolerated. In health, the direct effects of camicinal are on accelerating GET with a potential secondary benefit of reducing reflux events, which warrant further exploration in patient cohorts.

Modulation of LPS-induced pulmonary neutrophil infiltration and cytokine production by the selective PPARbeta/delta ligand GW0742

OBJECTIVE

To define the anti-inflammatory effects of PPARbeta/delta activation by use of the selective PPARbeta/delta ligand (GW0742) in a model of lipopolysaccharide (LPS)-induced pulmonary inflammation.

METHODS

Male BALB/c mice were pretreated for three days with the PPARbeta/delta agonist, GW0742, prior to induction of LPS-mediated pulmonary inflammation. Bronchial alveolar lavage fluid (BALF) was analyzed for inflammatory cell influx and for levels of pro-inflammatory mediators. BALF-derived inflammatory cells were also collected for mRNA analysis.

RESULTS

Pretreatment with GW0742 resulted in a significant decrease in leukocyte recruitment into the pulmonary space. Protein and mRNA levels of the pro-inflammatory cytokines IL-6, IL-1beta and TNFalpha in BALF were found to be significantly decreased in GW0742-treated animals (30 mg/kg). A significant decrease in granulocyte macrophage-colony stimulating factor (GM-CSF), a major regulator of neutrophil chemotaxis (via its downstream actions on TNFalpha and other cytokines/chemokines), activation and survival, was also noted in the BALF levels of GW0742-treated animals.

CONCLUSIONS

The present study demonstrates that activation of PPARbeta/delta attenuates the degree of inflammation in a model of LPS-induced pulmonary inflammation and may therefore represent a novel therapeutic approach for the treatment of inflammation-mediated pathologies.

Inhibition of Phosphodiesterase Type 4 Decreases Stress-Induced Defecation in Rats and Mice

BACKGROUND/AIMS

Phosphodiesterase type 4 (PDE4) has been previously shown to regulate colonic contractile activity in vitro. In this study, the effects of PDE4 inhibition were assessed in a model of stress-induced defecation previously demonstrated to be due to increased colonic transit/evacuation.

METHODS

Rats were individually placed in a mild restraint cage and placed into a 12 degrees C environment (cold-restraint stress) for 60 min. Mice received restraint (only) stress at room temperature for 30 min. Loperamide (positive control compound) or two different PDE4 inhibitors (rolipram and roflumilast) were administered orally at several doses to the rodents 1 h before stress began. Vehicle alone was administered for comparison. The number of fecal pellets expelled during stress (fecal pellet output), total fecal pellet wet weight and total fecal water content were measured.

RESULTS

Loperamide produced a dose-related decrease (ID(50)s in mg/kg) in fecal pellet output (rat = 7.4, mouse = 0.7) and significantly decreased fecal wet weight (72.9%) and decreased fecal percent water content (9.4%). The two PDE4 inhibitors produced a similar dose-related inhibition of fecal pellet output. Rolipram exhibited ID(50)s in rat and mouse of 14.1 and 27.1, respectively. Rolipram significantly decreased fecal wet weight (58.8%) but increased fecal percent water content (15.0%). For roflumilast, ID(50)s were 24.2 mg/kg and 12.4 in the rat and mouse, respectively. Although roflumilast also significantly (p < 0.05) decreased fecal wet weight (47.2%), it did not significantly increase fecal percent water content.

CONCLUSIONS

These data indicate that PDE4 inhibition is effective in reducing rodent stress-induced defecation, provides the first functional data on a potential role for PDE4 activity in the colonic evacuation response to stress, and indicates the potential utility of PDE4 inhibitors in functional bowel disease such as irritable bowel syndrome requires further evaluation.

Constitutive deletion of the serotonin-7 (5-HT7) receptor decreases electrical and chemical seizure thresholds

The localization of serotonin-7 (5-HT(7)) receptors and the biological activity of ligands have suggested that 5-HT(7) receptors might be involved in pain, migraine, epilepsy, anxiety, depression, memory, and sleep. In the present study, the potential involvement of 5-HT(7) receptors in epilepsy and other seizure disorders was assessed by comparing the seizures produced by three types of electrical stimulation and three chemical convulsants in 5-HT(7) receptor-deficient (knockout, KO) mice to those seizures observed in wild-type (WT) mice. Thresholds for producing electroshock-induced clonic seizures did not differ between KO versus WT mice. However, thresholds for producing electroshock-induced tonic seizures were significantly lower in KO than in WT mice. Seizures produced by pentylenetetrazole (PTZ, a GABA(A) receptor antagonist), N-methyl-d-aspartate (NMDA, an agonist at NMDA-type glutamate receptors), and cocaine (an inhibitor of monoamine uptake) were also studied. PTZ was more potent in inducing seizures in 5-HT(7) KO mice than in wild-type mice. Likewise, cocaine was more potent in inducing seizures in 5-HT(7) KO than in WT mice; moreover, death resulted from cocaine administration in 5-HT(7) KO mice but not in WT mice. There was a similar trend for NMDA that did not reach statistical significance. The present findings point to the potential for a generalized reduction in seizure threshold with constitutive deletion of the 5-HT(7) receptor gene. Since seizures have not been reported with pharmacological blockade of the receptor, the findings suggest that adaptive changes may play a role in the low seizure thresholds in these mice. In addition, the data suggest that the lower thresholds for seizures produced by diverse mechanisms should be taken into account when interpreting other aspects of the phenotype and behavioral pharmacology of this mouse.

The seizure-related phenotype of brain-derived neurotrophic factor knockdown mice

The present investigation focused on the seizure-related phenotype of mice lacking one allele of brain-derived neurotrophic factor. Thresholds for producing seizures in brain-derived neurotrophic factor wild-type and brain-derived neurotrophic factor heterozygous mice were compared in several seizure models, including thresholds for electrically-induced clonic, tonic-clonic and 6 Hz limbic seizures, as well as seizures induced chemically by kainate, pilocarpine and pentylenetetrazol. In addition, the rate of amygdala kindling, as well as pre- and post-kindling seizure thresholds was determined. Seizure thresholds for clonic and tonic-clonic electrically induced seizures did not differ between brain-derived neurotrophic factor wild-type and heterozygous mice. However, heterozygous mice had higher thresholds for 6 Hz limbic seizures compared with wild-type mice. Heterozygous mice also required larger doses of kainate to produce limbic seizures. Somewhat surprisingly, heterozygous mice required significantly lower doses of pilocarpine to produce limbic seizures. However, heterozygous mice required a higher dose of pentylenetetrazol to induce twitches, but not clonic seizures, compared with wild-type mice. In addition, heterozygous mice required more current to elicit focal afterdischarges in the amygdala both pre- and post-kindling than did wild-type mice, and, heterozygous mice kindled more slowly than wild-type mice. The present findings provide additional support for the hypothesis that brain-derived neurotrophic factor is involved not only in normal excitability, but may also be involved in abnormal excitability such as occurs in seizure disorders and epileptogenesis.

The antihyperalgesic effects of the T-type calcium channel blockers ethosuximide, trimethadione, and mibefradil

The purpose of the present study was to explore the analgesic effects of the low voltage-activated T-type Ca2+ channel blockers ethosuximide, trimethadione, and mibefradil in persistent and acute nociceptive tests. The anticonvulsant effects of the compounds were also determined in the intravenous pentylenetetrazol seizure model. Following intraperitoneal administration, ethosuximide and trimethadione dose-dependently reversed capsaicin-induced mechanical hyperalgesia. Similarly, the highest dose of mibefradil tested (30 microg, intracisternal) reversed capsaicin-induced mechanical hyperalgesia. Ethosuximide and mibefradil produced statistically significant analgesic effects in both early and late phase formalin-induced behaviors and trimethadione reduced late phase behaviors. Additionally, ethosuximide and trimethadione produced antinociceptive effects in the rat-tail flick reflex test. In contrast, following intracisternal administration, mibefradil had no effect in the tail flick reflex test. In addition, the anticonvulsants ethosuximide and trimethadione increased the doses of pentylenetetrazol required to produce both first twitch and clonic seizures. In contrast however, mibefradil had no anticonvulsant effect. The present results demonstrate that the clinically used anticonvulsants ethosuximide and trimethadione provide analgesic effects at doses, which are anticonvulsant. Furthermore, the data further supports the idea that T-type Ca2+ channels may be important targets for treating persistent pain syndromes.

Behavioral and convulsant effects of the (S) enantiomer of the group I metabotropic glutamate receptor agonist 3,5-DHPG in mice

The purpose of the present studies was to investigate the behavioral and convulsant effects produced by the group I metabotropic glutamate receptor agonist (S)-3,5-dihydroxyphenylglycine (DHPG). Administered i.c.v. to mice, (S)-3,5-DHPG produced a behavioral syndrome consisting of scratching and/or facial grooming, tremors, slow forelimb clonus, rearing, and falling that increased over the dose range of 10-400 nmol. The full syndrome, produced by 400 nmol of (S)-3,5-DHPG, was antagonized by the selective mGlu1 receptor antagonist LY456236 but not by the mGlu5 receptor antagonist MPEP or the mGlu2/3 receptor antagonist LY341495. The behaviors induced by the 400 nmol dose were not blocked by the NMDA receptor antagonist MK-801, but were attenuated by the non-NMDA receptor antagonists GYKI 52466 and NBQX, and the Ca2+ mobilization inhibitor dantrolene, but at motor-impairing doses. The scratching behaviors produced by 30 nmol of (S)-3,5-DHPG were antagonized by LY456236 but not by MPEP, LY341495 or MK-801. GYKI 52466 and dantrolene, but not NBQX, inhibited scratching at motor-impairing doses. Both 400 and 30 nmol of (S)-3,5-DHPG produced a generalized seizure as recorded by surface EEG electrodes. LY456236 blocked the seizures produced by 30 nmol but not by 400 nmol; dantrolene was ineffective in blocking seizures produced by either dose. The present findings suggest that (S)-3,5-DHPG produces an increase in excitation that is mediated by mGlu1 and non-NMDA receptors.

Comparison of the effect of glutamate receptor modulators in the 6 Hz and maximal electroshock seizure models

Glutamatergic ionotropic and metabotropic receptor modulators have been shown to produce anticonvulsant activity in a number of animal seizure models, e.g. maximal electroshock (MES) and DBA/2 sensory-induced seizures. The 6 Hz model of partial seizures is an alternative low frequency, long duration stimulation paradigm resulting in a seizure characterized by jaw and forelimb clonus, immobility, and an elevated tail (Straub-tail). A unique aspect of this model is that it is the only acute electrically-induced seizure model in which levetiracetam has displayed anticonvulsant activity, suggesting that the 6 Hz seizure model may be useful in identifying compounds with unique anticonvulsant profiles. The purpose of the present study was to examine the role of glutamate receptors in the MES and 6 Hz seizure models using a number of NMDA, AMPA/KA, and mGlu receptor modulators. The pharmacological profile of the 6 Hz seizure model was compared to that of the MES model using eight ionotropic glutamate receptor antagonists and eight mGlu receptor modulators. The ionotropic receptor antagonists MK-801, LY235959, NBQX, LY293558, GYKI 52466, LY300168, and LY377770 produced complete protection from tonic extension in the MES model. Furthermore, the noncompetitive mGlu1 (LY456236) and mGlu5 (MPEP) metabotropic receptor antagonists and the mGlu8 metabotropic receptor agonist (PPG) were also effective in the MES model whereas the competitive mGlu1 (LY367385) receptor antagonist, the mGlu2/3 (LY379268 and LY389795) and Group III (L-AP4) metabotropic receptor agonists were ineffective. In contrast, all of the compounds tested, produced dose-dependent protection in the 6 Hz model with an increase in potency as compared to the MES model. The largest protective indices (P.I.=TD50/ED50) observed were associated with the iGlu5 antagonist LY382884 and the mGlu2/3 receptor agonists LY379268 and LY389795 (P.I.=>14, 14, and 4.9, respectively) in the 6 Hz model. The results from the present study support the continued search for glutamate receptor modulators as potential antiepileptic agents. Furthermore these results illustrate the importance of using several different animal seizure models in the search for novel AEDs and the potential utility of the 6 Hz seizure model in identifying novel AEDs.

The effect of CGX-1007 and CI-1041, novel NMDA receptor antagonists, on NMDA receptor-mediated EPSCs

The N-methyl-D-aspartate (NMDA) receptor-gated ion channel is comprised of at least one NR1 subunit and any of four NR2 subunits (NR2A-D). The NR2 subunit confers different pharmacological and kinetic properties to the receptor. CGX-1007 (Conantokin G), a 17-amino acid polypeptide isolated from the venom of Conus geographus, is a novel NMDA receptor antagonist that is thought to be selective for the NR2B subunit. CGX-1007 has been reported to have highly potent, broad-spectrum anticonvulsant activity in animal seizure models. CI-1041 is an investigational compound, which also possesses anticonvulsant activity and has been shown to be highly selective for NR2B containing NMDA receptors. Although both CI-1041 and CGX-1007 are reportedly NR2B specific antagonists, they differ in their ability to block amygdala-kindled seizures, suggesting that the mechanism of action of these compounds differs. The present study was designed to test the hypothesis that CI-1041 and CGX-1007 would differentially modulate the function of NMDA receptors at excitatory synapses. Using the whole cell patch clamp technique, CGX-1007 and CI-1041 were found to block CA1 pyramidal cell, NMDA receptor-mediated excitatory postsynaptic currents (N-EPSCs) in a concentration-dependent manner in hippocampal slices from P4-P6 animals. In contrast, only CGX-1007 decreased NMDA receptor-mediated EPSC peak amplitude in slices from adult animals. The CGX-1007 block of peak amplitude was accompanied by a similar concentration-dependent decrease in decay kinetics of NMDA receptor-mediated EPSCs. These results suggest that while CI-1041 may be selective for NMDA receptors containing the NR2B subunit, CGX-1007 appears to be less selective than previously reported.

The effect of CGX-1007 and CI-1041, novel NMDA receptor antagonists, on kindling acquisition and expression

CGX-1007, a 17-amino acid polypeptide isolated from the venom of Conus geographus, is a novel NMDA receptor antagonist that is selective for the NR2B subunit. CI-1041 (PD 196860; Co 200461) is a novel, orally available NR2B selective antagonist. Both compounds possess anticonvulsant activity in a variety of well-established animal seizure models. The present study was designed to assess the effects of CGX-1007 and CI-1041 on the acquisition and expression of kindled seizures. In the corneal kindled rat, CGX-1007 [Epilepsia 36 (1998) 39] and CI-1041, administered p.o., 2h prior to the kindling stimulation displayed time- and dose-dependent block of fully expressed corneal kindled seizures (ED50 = 300 pmol and 2.5mg/kg for CGX-1007 and CI-1041, respectively). In amygdala kindled rats, acute treatment with CGX-1007 blocked the secondarily generalized kindled seizure in a dose-dependent manner. Complete protection against the secondarily generalized seizure was only observed at a dose that produced behavioral impairment (4 nmol). Acute treatment with CI-1041 did not provide any notable protection against secondarily generalized seizures. Neither compound provided protection against the focal kindled seizure. Chronic i.c.v. infusion of CGX-1007 or chronic oral administration of CI-1041 did not delay the acquisition of amygdala kindling. The results from these studies suggest that NMDA receptors containing the NR2B subunit may contribute to the expression of fully kindled secondarily generalized seizures; however, they appear less important for the development of kindling. The differential results obtained with CGX-1007 and CI-1041 suggest that several classes of mechanistically distinct NR2B antagonists may exist and that CGX-1007 may be less specific as a NR2B receptor antagonist than initially reported.

Anticonvulsant profile and teratogenicity of N-methyl-tetramethylcyclopropyl carboxamide: a new antiepileptic drug

PURPOSE

The studies presented here represent our efforts to investigate the anticonvulsant activity of N-methyl-tetramethylcyclopropyl carboxamide (M-TMCD) and its metabolite tetramethylcyclopropyl carboxamide (TMCD) in various animal (rodent) models of human epilepsy, and to evaluate their ability to induce neural tube defects (NTDs) and neurotoxicity.

METHODS

The anticonvulsant activity of M-TMCD and TMCD was determined after intraperitoneal (i.p.) administration to CF#1 mice, and either oral or i.p. administration to Sprague-Dawley rats. The ability of M-TMCD and TMCD to block electrical-, chemical-, or sensory-induced seizures was examined in eight animal models of epilepsy. The plasma and brain concentrations of M-TMCD and TMCD were determined in the CF#1 mice after i.p. administration. The induction of NTDs by M-TMCD and TMCD was evaluated after a single i.p. administration at day 8.5 of gestation in a highly inbred mouse strain (SWV) that is susceptible to valproic acid-induced neural tube defects.

RESULTS

In mice, M-TMCD afforded protection against maximal electroshock (MES)-induced, pentylenetetrazol (Metrazol)-induced, and bicuculline-induced seizures, as well as against 6-Hz "psychomotor" seizures and sound-induced seizures with ED50 values of 99, 39, 81, 51, and 10 mg/kg, respectively. In rats, M-TMCD effectively prevented MES- and Metrazol-induced seizures and secondarily generalized seizures in hippocampal kindled rats (ED50 values of 82, 45, and 39 mg/kg, respectively). Unlike M-TMCD, TMCD was active only against Metrazol-induced seizures in mice and rats (ED50 values of 57 and 52 mg/kg, respectively). Neither M-TMCD nor TMCD was found to induce NTDs in SWV mice.

CONCLUSIONS

The results obtained in this study show that M-TMCD is a broad-spectrum anticonvulsant drug that does not induce NTDs and support additional studies to evaluate its full therapeutic potential.

Pharmacological characterization of the 6 Hz psychomotor seizure model of partial epilepsy

Originally described as a model of 'psychomotor seizures' (J. Pharmacol. Exp. Ther. (1953) 107-273), the 6 Hz corneal stimulation model was abandoned shortly after its description because of its lack of sensitivity to phenytoin. This observation is the basis for the present study designed to validate the 6 Hz seizure as a model of therapy-resistant epilepsy. The pharmacological profile of the 6 Hz seizure was determined at varying current intensities using seven established AEDs (phenytoin, carbamazepine, clonazepam, phenobarbital, ethosuximide, trimethadione, valproic acid) and five second-generation AEDs (lamotrigine, levetiracetam, felbamate, tiagabine, topiramate). The immediate early gene c-Fos was used as a marker of seizure-induced neuronal activation to help define those brain structures that were activated by 6 Hz corneal stimulation. At the current intensity required to produce a seizure in 97% of the population (CC97=22 mA), the 6 Hz seizure did not discriminate between clinical classes of AEDs tested. Increasing the current intensity by 50% (i.e. 32 mA) decreased the sensitivity of the 6 Hz seizure to phenytoin and lamotrigine. At a current intensity of 2 x CC97 (i.e. 44 mA), only two AEDs, levetiracetam and valproic acid, displayed complete protection against the 6 Hz seizure, though the efficacy of these drugs was reduced when compared to the lower stimulation intensities. Intense c-Fos staining from 6 Hz seizures induced by 22 and 32 mA stimulus intensities remained localized to the amygdala and piriform cortex. Increasing the stimulus intensity to 44 mA resulted in additional heavy staining of the dentate gyrus. This recruitment of the dentate gyrus may account for the decrease in potency of levetiracetam and valproic acid at 44 mA. The pharmacological results combined with the c-Fos immunohistochemistry suggest that the 6 Hz stimulation may provide a useful model of therapy-resistant limbic seizures.

Conversational patterns of two-year-old twins in mother-twin-twin triads

This study investigated the general nature of conversational interaction in mother-twin-twin triads. Four sets of firstborn twins (2;3) were videotaped during 15 minutes of free play with their mothers. Analyses revealed that triadic conversations were approximately five times longer, and elicited more turns from all speakers, than dyadic conversations between mother and a single twin. Twins also responded as often to comments and requests made to another person as to those directed to themselves, but responded more often to questions directly to them than to others, indicating reliable monitoring of language not addressed to them. These results largely parallel those reported for mother-infant-sibling triads and indicate the unique effects of triadic exchanges are not due to the relative linguistic levels of the child partners.

Intermittent vertical supranuclear ophthalmoplegia and ataxia

A 6-year-old girl is described with a history of episodes of severe ataxia precipitated by fever since the age of 11 months and in whom mental and physical development was otherwise normal. The ataxia was associated with a complete vertical supranuclear ophthalmoplegia and normal horizontal eye movements. After resolution of the attack she had no abnormal movement of her limbs or clinical evidence of ophthalmoplegia, though electro-oculograms showed a persistent mild deficit of vertical saccades. In between the attacks hyperglycinuria, an elevated plasma glycine level (687 mumol L(-1], and negative screening for organic aciduria suggest that she may have nonketotic hyperglycinaemia. To our knowledge, intermittent vertical supranuclear ophthalmoplegia and ataxia in a normally developing child has not been reported previously.

Arrhinencephaly associated with a deficiency involving chromosome 18

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