Genome-Wide Association Study Identifies a Functional SIDT2 Variant Associated With HDL-C (High-Density Lipoprotein Cholesterol) Levels and Premature Coronary Artery Disease.

Objective: Low HDL-C (high-density lipoprotein cholesterol) is the most frequent dyslipidemia in Mexicans, but few studies have examined the underlying genetic basis. Our purpose was to identify genetic variants associated with HDL-C levels and cardiovascular risk in the Mexican population. Approach and Results: A genome-wide association studies for HDL-C levels in 2335 Mexicans, identified four loci associated with genome-wide significance: CETP, ABCA1, LIPC, and SIDT2. The SIDT2 missense Val636Ile variant was associated with HDL-C levels and was replicated in 3 independent cohorts (P=5.9×10−18 in the conjoint analysis). The SIDT2/Val636Ile variant is more frequent in Native American and derived populations than in other ethnic groups. This variant was also associated with increased ApoA1 and glycerophospholipid serum levels, decreased LDL-C (low-density lipoprotein cholesterol) and ApoB levels, and a lower risk of premature CAD. Because SIDT2 was previously identified as a protein involved in sterol transport, we tested whether the SIDT2/Ile636 protein affected this function using an in vitro site-directed mutagenesis approach. The SIDT2/Ile636 protein showed increased uptake of the cholesterol analog dehydroergosterol, suggesting this variant affects function. Finally, liver transcriptome data from humans and the Hybrid Mouse Diversity Panel are consistent with the involvement of SIDT2 in lipid and lipoprotein metabolism. Conclusions: This is the first genome-wide association study for HDL-C levels seeking associations with coronary artery disease in the Mexican population. Our findings provide new insight into the genetic architecture of HDL-C and highlight SIDT2 as a new player in cholesterol and lipoprotein metabolism in humans.

Anorectic interaction and safety of 5-hydroxytryptophan/carbidopa plus phentermine or diethylpropion in rat.

Drug combinations are being studied as potential therapies to increase the efficacy or improve the safety profile of weight loss medications. This study was designed to determine the anorectic interaction and safety profile of 5-hydroxytryptophan (5-HTP)/carbidopa + diethylpropion and 5-HTP/carbidopa + phentermine combinations in rats. The anorectic effect of individual drugs or in combination was evaluated by the sweetened milk test. Isobologram and interaction index were employed to determine the anorectic interaction between 5-HTP/carbidopa and diethylpropion or phentermine. Plasma serotonin (5-HT) was measured by ELISA. Safety of repeated doses of both combinations in rats was evaluated using the tail sphygmomanometer, cardiac ultrasound, hematic biometry and blood chemistry. A single oral 5-HTP, diethylpropion or phentermine dose increased the anorectic effect, in a dose-dependent fashion, in 12 h-fasted rats. A dose of carbidopa at 30 mg/kg reduced the 5-HTP-induced plasmatic serotonin concentration and augmented the 5-HTP-induced anorectic effect. Isobologram and interaction index indicated a potentiation interaction between 5-HTP/30 mg/kg carbidopa + diethylpropion and 5-HTP/30 mg/kg carbidopa + phentermine. Chronic administration of experimental ED40 of 5-HTP/30 mg/kg carbidopa + phentermine, but not 5-HTP/30 mg/kg carbidopa + diethylpropion, increased the mitral valve leaflets area. Moreover, there were no other significant changes in cardiovascular, hematic or blood parameters. Both combinations induced around 20% body weight loss after 3 months of oral administration. Results suggest that 5-HTP/30 mg/kg carbidopa potentiates the anorectic effect of diethylpropion and phentermine with an acceptable safety profile, but further clinical studies are necessary to establish their therapeutic potential in the obesity treatment.

Correction to: Superior silybin bioavailability of silybin-phosphatidylcholine complex in oily-medium soft-gel capsules versus conventional silymarin tablets in healthy volunteers.

AbstractFollowing publication of the original article [1], the author reported their given name have been erroneously tagged as their family names.

Superior silybin bioavailability of silybin-phosphatidylcholine complex in oily-medium soft-gel capsules versus conventional silymarin tablets in healthy volunteers.

BACKGROUND: Fibrosis is a response to chronic liver disease that results in excessive accumulation of extracellular matrix proteins and formation of scar tissue. Fibrosis represents a clinical challenge of worldwide significance. Several studies have demonstrated that many natural products and herbal medicines have activity against liver fibrosis, and extracts of milk thistle such as silymarin and silybin are the natural compounds most commonly prescribed for liver diseases. Therefore, we sought to assess and compare the pharmacokinetic properties and bioavailability of silybin-phosphatidylcholine complex in oily-medium soft-gel capsules and conventional silymarin tablets in healthy Mexican volunteers. METHODS: We enrolled 23 healthy volunteers to participate in a prospective, balanced, blind, single-dose, two-way crossover study with a one-week washout period. Fasting participants received either 45 mg silybin-phosphatidylcholine complex or 70 mg silymarin to assess which formulation provided better bioavailability of silybin. Plasma was obtained and analysed for silybin concentration using a validated ultra-performance liquid chromatography-tandem mass spectroscopy method. Pharmacokinetic parameters were obtained by non-compartmental analysis and values were compared by analysis of variance for a crossover design. Ratios of maximum plasma drug concentration and area under the curve (AUC) were obtained and 90% confidence intervals were calculated. RESULTS: The 23 healthy subjects (11 women, 12 men) who participated in the study were aged 22-31 years old (average: 28), average weight 64.8 kg, height 1.65 m and body mass index 23.5 kg/m2. Plasma levels of silybin were higher after the administration of silybin-phosphatidylcholine complex capsules compared with that after conventional silymarin tablets (P <  0.0001). CONCLUSIONS: The silybin-phosphatidylcholine complex in oily-medium soft-gel capsules seems to provide superior bioavailability. However, clinical studies must be performed to demonstrate its clinical relevance in the treatment of liver diseases. TRIAL REGISTRATION: NCT03440164 ; registered on November 11, 2016.

Genetic contributors to serum uric acid levels in Mexicans and their effect on premature coronary artery disease.

BACKGROUND: Serum uric acid (SUA) is a heritable trait associated with cardiovascular risk factors and coronary artery disease (CAD). Genome wide association studies (GWAS) have identified several genes associated with SUA, mainly in European populations. However, to date there are few GWAS in Latino populations, and the role of SUA-associated single nucleotide polymorphisms (SNPs) in cardiovascular disease has not been studied in the Mexican population. METHODS: We performed genome-wide SUA association study in 2153 Mexican children and adults, evaluated whether genetic effects were modified by sex and obesity, and used a Mendelian randomization approach in an independent cohort to study the role of SUA modifying genetic variants in premature CAD. RESULTS: Only two loci were associated with SUA levels: SLC2A9 (ß = -0.47 mg/dl, P = 1.57 × 10-42 for lead SNP rs7678287) and ABCG2 (ß = 0.23 mg/dl, P = 2.42 × 10-10 for lead SNP rs2231142). No significant interaction between SLC2A9 rs7678287 and ABCG2 rs2231142 genotypes and obesity was observed. However, a significant ABCG2 rs2231142 genotype*sex interaction (P = 0.001) was observed in adults but not in children. Although SUA levels were associated with premature CAD, metabolic syndrome and decreased glomerular filtration rate (eGFR), only ABCG2 rs2231142 was associated with decreased eGFR in the premature CAD group. CONCLUSIONS: SUA elevation was independently associated with premature CAD, metabolic syndrome and decreased eGFR in the Mexican population. However, a Mendelian randomization approach using the lead SUA-associated SNPs (SLC2A9 and ABCG2) did not support a causal role of elevated SUA levels for premature CAD.

Antinociceptive effect of (-)-epicatechin in inflammatory and neuropathic pain in rats.

The aim of this study was to investigate the antinociceptive potential of (-)-epicatechin and the possible mechanisms of action involved in its antinociceptive effect. The carrageenan and formalin tests were used as inflammatory pain models. A plethysmometer was used to measure inflammation and L5/L6 spinal nerve ligation as a neuropathic pain model. Oral (-)-epicatechin reduced carrageenan-induced inflammation and nociception by about 59 and 73%, respectively, and reduced formalin- induced and nerve injury-induced nociception by about 86 and 43%, respectively. (-)-Epicatechin-induced antinociception in the formalin test was prevented by the intraperitoneal administration of antagonists: methiothepin (5-HT1/5 receptor), WAY-100635 (5-HT1A receptor), SB-224289 (5-HT1B receptor), BRL-15572 (5-HT1D receptor), SB-699551 (5-HT5A receptor), naloxone (opioid receptor), CTAP (µ opioid receptor), nor-binaltorphimine (κ opioid receptor), and 7-benzylidenenaltrexone (δ1 opioid receptor). The effect of (-)-epicatechin was also prevented by the intraperitoneal administration of L-NAME [nitric oxide (NO) synthase inhibitor], 7-nitroindazole (neuronal NO synthase inhibitor), ODQ (guanylyl cyclase inhibitor), glibenclamide (ATP-sensitive K channel blocker), 4-aminopyridine (voltage-dependent K channel blocker), and iberiotoxin (large-conductance Ca-activated K channel blocker), but not by amiloride (acid sensing ion channel blocker). The data suggest that (-)-epicatechin exerts its antinociceptive effects by activation of the NO-cyclic GMP-K channels pathway, 5-HT1A/1B/1D/5A serotonergic receptors, and µ/κ/δ opioid receptors.

Low doses of tizanidine synergize the anti-nociceptive and anti-inflammatory effects of ketorolac or naproxen while reducing of side effects.

The aim of the present study was to determine whether tizanidine, an alpha2-adrenoceptor agonist, is able to increase the anti-inflammatory and anti-nociceptive effects of naproxen and ketorolac with a low incidence of gastric injury and spontaneous activity in rats. The anti-inflammatory effect was assayed in a carrageenan test, and oral administration of tizanidine (ED40 =0.94±0.2mg/kg), naproxen (ED40=3.18±0.4mg/kg), and ketorolac (ED40=16.4±1.9mg/kg) showed a dose-dependent effect on inflammation. The anti-nociceptive effect was assayed in the formalin test, and administration of tizanidine (ED40=0.39±0.06mg/kg, p.o.), naproxen (ED40=33.9±3.9mg/kg, p.o.) or ketorolac (ED40=6.49±1mg/kg, p.o.) each showed a dose-dependent anti-nociceptive effect. The effects of combinations of tizanidine/naproxen and tizanidine/ketorolac were determined considering their ED40 at a rate of 1:1. Additionally, the tizanidine/naproxen and tizanidine/ketorolac combinations showed anti-inflammatory and anti-nociceptive effects. The tizanidine/ketorolac combination was more potent than tizanidine/naproxen, in both inflammatory (interaction index=0.03 tizanidine/ketorolac and 0.07 tizanidine/naproxen) and nociceptive (interaction index=0.005 tizanidine/ketorolac and 0.01 tizanidine/naproxen) processes. In both cases, tizanidine improved naproxen and ketorolac gastrointestinal tolerability by 50%. Furthermore, co-administration of tizanidine with naproxen or ketorolac did not modify the spontaneous activity in the same way as individual tizanidine administration. Considering that tizanidine increases the anti-inflammatory and anti-nociceptive effects of naproxen or ketorolac, with an increase in gastric tolerability, tizanidine could provide therapeutic advantages in the clinical treatment of inflammation and pain.

Proglumide enhances the antinociceptive effect of cyclooxygenase inhibitors in diabetic rats in the formalin test.

The purpose of this study was to assess the effect of the non-selective cholecystokinin receptor antagonist proglumide on the antinociceptive activity of ketorolac and meloxicam in non-diabetic and diabetic rats. Streptozotocin (60 mg/kg) injection caused hyperglycemia which was maintained for 2 weeks. Formalin-evoked flinching was increased in diabetic rats as compared to non-diabetic rats. Local peripheral ipsilateral, but not contralateral, administration of ketorolac and meloxicam produced antinociception in non-diabetic and diabetic rats. However, the antinociceptive effect of both drugs was significantly reduced in diabetic animals. Proglumide was ineffective by itself and it did not affect the antinociception induced by the cyclooxygenase inhibitors in non-diabetic rats. Contrariwise, proglumide reduced formalin-induced nociception and it increased ketorolac- or meloxicam-induced antinociception in diabetic rats. These results suggest that peripheral cholecystokinin plays an important role in diabetes-induced sensitization as well as in the reduction of the antinociceptive effects of ketorolac and meloxicam in diabetic rats. The combination of cholecystokinin receptor antagonists and ketorolac or meloxicam may be a useful strategy to reduce nociception in diabetic patients.

Effects of a cyclooxygenase-2 preferential inhibitor in young healthy dogs exposed to air pollution: a pilot study.

Residency in cities with high air pollution is associated with neuroinflammation and neurodegeneration in healthy children, young adults, and dogs. Nonsteroidal anti-inflammatory drugs may offer neuroprotection. The authors measured the plasma concentrations of 3-nitrotyrosine and the cerebro-spinal-fluid concentrations of prostaglandin E2 metabolite and the oligomeric form of amyloid derived diffusible ligand; measured the mRNA expression of cyclooxygenase-2, interleukin 1beta, CD14, and Aquaporin-4 in target brain areas; and evaluated brain MRI, cognition, and neuropathology in 8 dogs treated with a preferential cyclooxygenase-2 inhibitor (Nimesulide) versus 7 untreated litter-matched Mexico City dogs. Nimesulide significantly decreased nitrotyrosine in plasma (p < .0001), frontal gray IL1beta (p = .03), and heart IL1beta (p = .02). No effect was seen in mRNA COX2, amyloid, and PGE2 in CSF or the MRI white matter lesions. All exposed dogs exhibited olfactory bulb and frontal accumulation of Abeta(42) in neurons and blood vessels and frontal vascular subcortical pathology. White matter hyperintense MRI frontal lesions were seen in 4/6 non-treated and 6/8 treated dogs. Nonsteroidal anti-inflammatory drugs may offer limited neuroprotection in the setting of severe air pollution exposures. The search for potentially beneficial drugs useful to ameliorate the brain effects of pollution represents an enormous clinical challenge.

Comparative bioavailability of two oral formulations of omeprazole.

Omeprazole is a very widely used proton-pump inhibitor. Currently, there are several branches available in Mexico, however, limited information about their bioavailabilities is available. The purpose of this study was to compare the bioavailability of two of them, Losec and Omelcid. Twenty-eight healthy volunteers were enrolled in this study that was carried out following the recommendations of the Declaration of Helsinki. Subjects read the protocol that was approved by the institutional research and ethics committees and gave written consent for participation. After an overnight fast, volunteers received an oral dose of 20 mg omeprazole (formulation A or B) and blood samples were obtained at selected times during 8 hours. Plasma was obtained by centrifugation and stored frozen until analyzed by a validated HPLC method. Pharmacokinetic parameters were obtained by non-compartmental analysis and values (+/- s.e.m.) obtained were as follows: Cmax 354.28 +/- 51.57 and 308.95 +/- 44.42 ng/ml, t(max) 2.26 +/- 0.22 and 2.63 +/- 0.24 h and AUC(8h) 701.01 +/- 109.34 and 774.13 +/- 132.84 ngh/ml for formulations A and B respectively. Log transformed Cmax and AUC(8h) were compared by analysis of variance and 90% confidence limits of the parameters ratios (B/A) were 72.73-106.34% and 90.32-124.96%, for Cmax and AUC(8h) respectively. As confidence intervals did not exceed the 70-142.9% limits for Cmax and 80-125% for AUC(8h), it is concluded that the formulations tested are bioequivalent.

The influence of malnutrition on the oral pharmacokinetics of nimesulide in rats.

Malnutrition is a health problem in Mexico. It has been established that malnutrition may produce important changes in the pharmacological response to drugs, since changes in the pharmacodynamics and pharmacokinetics may occur. It has been described that a reduction of plasma proteins and in hepatic enzymes may occur. Due to these changes, absorption, distribution and elimination of drugs can be modified. Nimesulide is a non-steroidal anti-inflammatory agent that is widely used. This drug is importantly bound to plasma proteins and is metabolized through cytochrome P-450, two systems that are altered in malnutrition. In order to establish if malnutrition can modify the pharmacokinetics of nimesulide, a comparison of pharmacokinetic parameters obtained in control and protein-calorie malnourished rats was carried out. Two groups of 7 rats were employed in this study. At 45 days of age, group 1 received a standard balanced diet for 4 weeks, whereas, group 2 received a low protein diet for the same period. Then, rats received an oral dose of 10 mg/kg nimesulide and blood samples were drawn at selected times for 12 hr. Nimesulide whole blood levels were determined by HPLC and the pharmacokinetic parameters; Cmax 1.18 +/- 0.13 and 1.03 +/- 0.10 microg/ml, tmax 5.25 +/- 1.03 and 7.48 +/- 1.09 h and AUC12h 8.64 +/- 1.19 and 8.27 +/- 0.85 microg x h/ml were obtained. We conclude that malnutrition does not modify the oral pharmacokinetics of nimesulide.

Comparison of suspension composition on the pharmacokinetics of nimesulide in rats.

Nimesulide is a non-steroidal anti-inflammatory agent that is widely used in the treatment of inflammatory pain. The drug belongs to the class II of Biopharmaceutical Classification System (low solubility, high permeability) and therefore, absorption of this drug is limited by its dissolution. It has been established that complex formation of insoluble substances with cyclodextrins may increase their oral bioavailability since solubility is improved. In order to provide test this hypothesis, a comparison on the oral pharmacokinetics of two suspensions of nimesulide in rats was carried out. Two groups of 7 rats were employed. One group received an oral dose of 10 mg/kg of a suspension prepared with 0.5% carboxymethylcellulose solution in water, whereas the other group received a commercially available formulation containing the complex of nimesulde-beta cyclodextrins (Eskaflam). Blood samples were obtained at selected times for a period of 12 hours and analyzed by an HPLC method. Pharmacokinetic parameters obtained were as follows: Cmax 1.18 +/- 0.16 and 1.93 +/- 0.12 microg/ml, tmax 5.25 +/- 1.03 and 3.21 +/- 0.91 h and AUC 8.65 +/- 1.19 and 13.74 +/- 0.70 microg hr/ml for carboxy-methylcellulose and Eskaflam, respectively. Values for Cmax and AUC12hr were increased and a reduction of tmax was observed indicating improved absorption of nimesulide in the formulation containing beta-cyclodextrins.

Comparison of the oral pharmacokinetics of fluconazole and itraconazole in Mexicans.

Fluconazole and itraconazole are antimycotics widely used in Mexico. However, limited information about their pharmacokinetics is available. It has been reported that physicochemical characteristics of these compounds are disparate, leading to different pharmacokinetic profiles. Moreover, it has been suggested that pharmacokinetics of some drugs may vary in Mexicans when compared with Caucasians due to reduced metabolism by CYP3A4. Based on these distinctions, it is important to carry out local studies in order to establish dosage regimens according the characteristics of each population. The purpose of this study was to compare the oral pharmacokinetics of fluconazole and itraconazole in Mexicans and to compare our results with those reported in other populations. Two groups of 16 subjects volunteered for this study that was approved by the Institutional Research and Ethics Committees. All subjects gave written informed consent for participation. After an overnight fast, volunteers received an oral dose of 100 mg fluconazole or itraconazole and blood samples were obtained at selected times over 96 hr. Plasma was obtained and analyzed by HPLC and pharmacokinetic parameters were obtained. As expected, fluconazole plasma levels were higher than itraconazole due to a lower volume of distribution. Additionally, less variability was observed for fluconazole. When data obtained in Mexicans was compared with those obtained in other populations, no differences were observed, suggesting that there are not interethnic differences in the pharmacokinetics of fluconazole and itraconazole.

Gender differences in the oral pharmacokinetics of fluconazole.

BACKGROUND AND OBJECTIVE: Fluconazole is a triazole derivative widely used for the treatment of mycoses. It has been established that several factors are able to modify its pharmacokinetics, including the bodyweight of the patient; however, there is controversy about the influence of gender on the pharmacokinetics of fluconazole. In order to clarify this controversy we decided to evaluate the pharmacokinetics of fluconazole in males and females. METHODS: Fifty-nine subjects (26 males and 33 females) were enrolled in this study. Volunteers received an oral dose of fluconazole 100mg under fasting conditions and blood samples were collected at selected times over a period of 96 hours. Plasma was obtained and analysed by a high-performance liquid chromatography method. RESULTS: The plasma fluconazole concentrations obtained in women were higher than those obtained in men. This was reflected in differences in most pharmacokinetic parameters. However, when parameters were normalised according to the bodyweight of subjects, differences were reduced, indicating that this factor plays a role in the differences observed. Notwithstanding, differences in other parameters, such as normalised maximum plasma concentration, time to reach maximum plasma concentration, volume of distribution and half-life, remained. CONCLUSION: Fluconazole pharmacokinetics are influenced by both bodyweight and gender, most likely because of differences in total body water between males and females. Although the clinical impact on efficacy and safety of the pharmacokinetic differences observed in this study was not established, it is desirable that fluconazole dosage regimens take into account both the gender and the bodyweight of the patient.

Peripheral participation of cholecystokinin in the morphine-induced peripheral antinociceptive effect in non-diabetic and diabetic rats.

The effects of cholecystokinin (CCK-8) and the CCK receptor antagonist proglumide, on antinociception induced by local peripheral (subcutaneous) injected morphine in non-diabetic (ND) and streptozotocin-induced diabetic (D) rats, were examined by means of the formalin test. Morphine induced dose-dependent antinociception both in ND and D rats. However, in D rats, antinociceptive morphine potency was about twofold less than in ND rats. Pre-treatment with CCK-8 abolished the antinociceptive effect of morphine in a dose-dependent manner in both groups of rats. Additionally, proglumide enhanced the antinociceptive effect induced by all doses of morphine tested. Both CCK-8 and proglumide had no effect on flinching behaviour when given alone to ND rats. Unlike ND rats, in D rats proglumide produced dose-dependent antinociception and CCK-8 enhanced formalin-evoked flinches, as observed during the second phase of the test. In conclusion, our data show a decrease in peripheral antinociceptive potency of morphine when diabetes was present. Additionally, peripheral CCK plays an antagonic role to the peripheral antinociceptive effect of morphine, additional to the well known CCK/morphine interaction at spinal and supraspinal level.

Bioequivalence of two oral formulations of glyburide (glibenclamide).

Glyburide (glibenclamide) is a sulfonylurea derivative that is very widely used in the treatment of type II diabetes mellitus. Currently, there are several pharmaceutical formulations available in Mexico containing this drug, however, very limited information about their bioavailabilities is known. The purpose of this study was to compare the bioavailability of two formulations of glyburide used in Mexico, Daonil and Gen-Glybe. Twenty-four Mexican healthy volunteers participated in this study that was carried out following the recommendations of the Declaration of Helsinki. Subjects received a dose of 10 mg of glyburide (two tablets of 5 mg) under fasting conditions in two separate sessions using a randomized crossover design with a one week washout period. Plasma samples were obtained at selected times over 24 hours and stored frozen until analyzed. Pharmacokinetic parameters were obtained and values (mean +/- S.E.M.) were as follows: Cmax 273.32 +/- 25.84 versus 294.83 +/- 27.12 ng/ml; tmax 3.03 +/- 0.23 versus 2.87 +/- 0.24 h; and AUC24h 1396.66 +/- 130.18 versus 1557.99 +/- 140.24 ng x h/ml, for Daonil and Gen-Glybe tablets, respectively. Pharmacokinetic parameters were compared using analysis of variance for a cross-over design and ratios of AUC24h and Cmax and 90% confidence intervals were obtained. As confidence intervals did not exceed the limits of acceptance (80--125%) for Cmax and AUC24h, it is concluded that the formulations tested are bioequivalent.

Kainic acid does not modify the oral pharmacokinetics of carbamazepine in rats.

Carbamazepine (CBZ) is a widely used antiepileptic agent that frequently interacts with other drugs. Recently, it has been reported that CBZ is able to modify the disturbed sleep patterns induced by kainic acid in epileptics. As a pharmacokinetic-pharmacodynamic characterization in the same animal is not possible due to the stress induced by blood sampling, it is important to establish if kainic acid is able to modify the pharmacokinetics of CBZ. Two groups of seven rats were used in this study. Animals received an oral dose of 50 mg/kg of CBZ alone or with 10 mg/kg of kainic acid. Blood samples (0.1 mL) were obtained at selected times for 12 hr and stored frozen until analyzed by HPLC. Pharmacokinetic parameters were: Cmax 6.51 +/- 1.32 and 6.63 +/- 0.95 microg/mL, tmax 3.55 +/- 0.98 and 1.82 +/- 0.59 hr, AUC 66.61 +/- 28.16 and 73.54 +/- 15.35 microg x h/mL and t1/2 7.16 +/- 2.55 and 5.80 +/- 1.37 hr. No statistically significant difference was observed in any parameter indicating that kainic acid is not able to modify oral pharmacokinetics of CBZ and pharmacokinetic-pharmacodynamic studies may be carried out using two groups of animals, one for the pharmacodynamics and another for the pharmacokinetic evaluation.

Involvement of cholecystokinin in peripheral nociceptive sensitization during diabetes in rats as revealed by the formalin response.

The possible pronociceptive role of peripheral cholecystokinin (CCK-8) as well as CCK(A) and CCK(B) receptors in diabetic rats was assessed. Subcutaneous injection of 0.5% formalin induced a greater nociceptive behavior in diabetic than in non-diabetic rats. Moreover, local peripheral injection of CCK-8 (0.1-100 microg) significantly increased 0.5% formalin-induced nociceptive activity in diabetic, but not in non-diabetic, rats. This effect was restricted to the formalin-injected paw as administration of CCK-8 into the contralateral paw was ineffective. Local peripheral administration of CCK-8, in the absence of formalin injection, produced a low level of, but significant increase in, flinching behavior in diabetic compared to non-diabetic rats. In addition, local peripheral administration of the non-selective CCK receptor antagonist proglumide (1-100 microg), CCK(A) receptor antagonist lorglumide (0.1-100 microg) or CCK(B) receptor antagonist CR-2945 (0.1-100 microg), but not vehicle or contralateral administration of CCK receptor antagonists, significantly reduced 0.5% formalin-induced flinching in diabetic rats. CR-2945 was the most effective drug in this condition. These effects were not observed in non-diabetic rats. The local peripheral pronociceptive effect of CCK-8 (100 microg) was significantly reduced by proglumide (100 microg), lorglumide (100 microg), and CR-2945 (100 microg). Results suggest that diabetes-induced peripheral sensitization could be due to a local peripheral release of CCK-8, which in turn would act on CCK(B), mainly but also in CCK(A), receptors located on the primary afferent neurons.

The nitric oxide-cyclic GMP-protein kinase G-K+ channel pathway participates in the antiallodynic effect of spinal gabapentin.

The possible participation of the nitric oxide (NO)-cyclic GMP-protein kinase G (PKG) pathway on gabapentin-induced spinal antiallodynic activity was assessed in spinal nerve injured rats. Intrathecal gabapentin, diazoxide or pinacidil reduced tactile allodynia in a dose-dependent manner. Pretreatment with NG-L-nitro-arginine methyl ester (L-NAME, non-specific inhibitor of NO synthase NOS), 7-nitroindazole (neuronal NO synthase inhibitor), 1H-[1,2,4] -oxadiazolo [4,3-a] quinoxalin-1-one (ODQ, guanylyl cyclase inhibitor) or (9S, 10R, 12R)-2,3,9,10,11,12-hexahydro-10-methoxy-2,9-dimethyl-1-oxo-9,12-epoxy-1H-diindolo-[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylic acid methyl ester (KT-5823, specific PKG inhibitor), but not NG-D-nitro-arginine methyl ester (D-NAME) or okadaic acid (protein phosphatase 1 and 2 inhibitor) prevented gabapentin-induced antiallodynia. Pinacidil activity was not blocked by L-NAME, D-NAME, 7-nitroindazole, ODQ, KT-5823 or okadaic acid. Moreover, KT-5823, glibenclamide (ATP-sensitive K+ channel blocker), apamin and charybdotoxin (small- and large-conductance Ca2+-activated K+ channel blockers, respectively), but not margatoxin (voltage-gated K+ channel blocker), L-NAME, 7-nitroindazole, ODQ or okadaic acid, reduced diazoxide-induced antiallodynia. Data suggest that gabapentin-induced spinal antiallodynia could be due to activation of the NO-cyclic GMP-PKG-K+ channel pathway.