Inhibition of ionotropic neurotransmitter receptors by antagonists: strategy to estimate the association and the dissociation rate constant of antagonists with very strong affinity to the receptors.

Since binding of an agonist to an ionotropic neurotransmitter receptor causes not only channel opening, but also desensitization of the receptor, inhibition of the receptor by the antagonist sometimes becomes very complicated. The transient state kinetics of ligand association and dissociation, and desensitization of the receptor were considered on the basis of the minimal model proposed by Hess' group, and the following possibilities were proposed. 1) When an agonist is simultaneously applied to the receptor with an antagonist whose affinity to the receptor is extremely strong and different from that of the agonist, it is usually impossible to estimate the real inhibition constant exactly from the responses because desensitization of the receptor proceeds before the equilibrium of the ligand binding. Simultaneous addition of the antagonist with strong affinity to the receptor may apparently accelerate inactivation (desensitization) of the receptor. The association rate constant of the antagonist can be estimated by analyses of the rate of the inactivation in the presence and the absence of the antagonist. 2) A preincubated antagonist with a slow dissociation rate constant, i.e., a very effective inhibitor, may cause apparent noncompetitive inhibition of the receptor, since the receptor is desensitized by an agonist as soon as the antagonist dissociates from the receptor and the dissociation of the antagonist from the receptor becomes the rate-determining step. A nicotinic acetylcholine receptor (nAChR) was expressed in Xenopus oocytes by injecting mRNA prepared from Electrophorus electricus electroplax and used for the experiments on inhibition by an antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Strychnos nux-vomica extract and its ultra-high dilution reduce voluntary ethanol intake in rats.

OBJECTIVES: To see whether Strychnos nux-vomica extract (mother tincture [MT]), its potency Nux 30c, and its principal alkaloid, strychnine, could reduce voluntary ethanol intake in rats. To analyze the solution structure of Nux MT, Nux 30c, 90% ethanol, and ethanol 30c by means of electronic (ES) and nuclear nuclear magnetic resonance (NMR) spectra. DESIGN: Potentially alcoholic rats were first given 20% ethanol and then kept on a two-choice bottle, one with 20% ethanol and another with tap water. These rats were given the following oral treatments for 15 days: group 1, control; group 2, strychnine at 0.36 mg/kg per day; group 3, ethanolic extract of S. nux-vomica seeds (Nux MT) at 3.6 mg/kg per day; and group 4, Nux 30c at 0.05 mL/d per rat. Nux 30c was prepared by successive dilution of Nux MT and 90% ethanol (1:100) and sonication at 20 kHz for 30 seconds in 30 steps. RESULTS: Both Nux MT and Nux 30c significantly reduced ethanol intake and increased water intake in rats. ES of two dilutions of Nux MT and Nux 30c showed intersections at more than one point suggesting existence of molecular complexes. ES of Nux MT in CCl4 showed a red shift when 90% ethanol was added indicating molecular complexation and charge transfer interaction between ethanol and Nux compounds. NMR spectra of Nux MT, 90% ethanol, ethanol 30c, and Nux 30c indicated a change in solution structure of the medium (90% ethanol) of Nux 30c. CONCLUSION: Nux MT and Nux 30c could reduce ethanol intake in rats. The altered solution structure of Nux 30c is thought to mimic Nux MT and produce ethanol aversion in rats.

Altered solution structure of alcoholic medium of potentized Nux vomica underlies its antialcoholic effect.

Nux vomica 30c, 200c and 1000c were administered orally to three batches of albino mice for three days. Six hours after the last dose on the third day the mice were injected i.p. with ethanol 4g/kg body wt. They lost their righting reflex and lay motionless apparently sleeping due to alcohol. Mice treated with three potencies of Nux vomica regained their righting reflex more quickly than the corresponding untreated controls. Each of the three batches of mice was tested twice for ethanol sedation, once with a potency of Nux vomica and another time with a placebo control. The time interval between drug treatment and control was 10 days. NMR spectra of Nux 30, Nux 200, Nux 1000, alcohol 30, alcohol 30 (unagitated) and 90% alcohol showed significant difference from each other with respect to the spin-lattice relaxation time (T1) of the deuterium nuclei. This gives a measurable physical basis of the effective high potencies of Nux vomica.

Reduction of alcohol induced sleep time in albino mice by potentized Nux vomica prepared with 90% ethanol.

UNLABELLED: Male adult albino mice were administered potentized Nux vomica 30 c (Nux v). The drug was mixed with sterile distilled water at 0.05 ml/2 ml water and given at 0.05 ml/individual. Control consisted of blank ethanol solution. Ethanolic extract from the seeds of Strychnos nuxvomica L was mixed with 90% ethanol 1:100 and sonicated for 30 s at 20 KHz. This was further diluted and sonicated in 30 steps to produce Nux v 30 c. Six hours after treatment, mice were given 25% ethanol i.p. at 4 g/kg body wt. The duration of sleep time starting from the loss of righting reflex until its restoration was recorded for each mouse. The duration of sleep time with ethanol was recorded in four sessions for the same group of mice with an interval of 10 d between sessions. TREATMENTS: session 1 with control solution, 2 with Nux v (oral), 3 with control solution and 4 with Nux v (i.p.). Nux v (oral) produced the shortest sleep time as compared to other treatments which did not differ from each other significantly with respect to sleep time. In another experiment Nux v 30 c was prepared with distilled water and pure absolute ethanol by the above process of successive dilution and sonication. These two preparations together with Nux v 30 c, prepared with 90% ethanol, were tested on mice for their effect on alcohol-induced sleep time. Only Nux v 30 c prepared with 90% ethanol was effective in reducing the sleep time in mice. It is concluded that the solution structure of ethanol/water mixture carries the specificity of the Nux v at ultra high dilution. It is further concluded that the effect is mediated through oral receptors.

Nux vomica 30 prepared with and without succession shows antialcoholic effect on toads and distinctive molecular association.

Adult toads, Bufo melanostictus, were administered Nux vomica (Nux v) 30 prepared with and without succussion on the tongue. The drug was mixed with sterile distilled water at the rate 0.05ml/ml water and given orally 0.05ml/individual. The control consisted of blank ethanol solution. Seeds of Strychnos nuxvomica were ground and extracted with 90% ethanol in the laboratory. Nux v 30 was prepared by successive dilution and succussion in 30 steps, Nux v 30 u was prepared by successive dilution only. Four hours after treatment, toads were given 25% ethanol i.p. at 8g/kg body weight. The duration of ethanol induced sleep time was recorded for each toad. Both Nux v 30 and Nux v 30 u significantly reduced ethanol induced sleep time in toads as compared to their respective controls. Electronic, infra red and nuclear magnetic resonance spectra of Nux v 30, Nux v 30 u and their diluent medium (90% ethanol) show marked differences from each other. These dilutions and ethanol 30 and ethanol 30 u show marked differences from each other with respect to spin-lattice relaxation time (T1) and chemical shift. The difference has been attributed to the variation in intra and inter-molecular association of ethanol and water.

Increase in brain prostaglandins during convulsions is due to increased neuronal activity and not to hypoxia.

The levels of prostaglandin D2 (PGD2) and prostaglandin F2 alpha (PGF2 alpha), being the major prostaglandins formed in mouse brain in vivo were determined using a radioimmunological technique. Under basal conditions, they were less than 8.49 ng/g for PGD2 and less than 3.76 ng/g for PGF2 alpha. During seizures, induced by the centrally acting convulsant pentylenetetrazol, cerebral concentrations of both prostaglandins were markedly enhanced as compared to basal conditions. The seizure evoked increase in brain prostaglandins could be attributed to the enhanced neuronal activity. If convulsions were induced with the spinal cord convulsant strychnine no increase in brain prostaglandins was seen although the occurring hypoxia was probably very similar. Therefore, hypoxia does not seem to play a significant role in the prostaglandin increase. The effect of pentylenetetrazol on cerebral prostaglandins was independent of the mechanical convulsions induced by the drug. Muscle relaxed mice showed the same increase in cerebral prostaglandins as convulsing mice. Muscle relaxation alone had no influence on prostaglandin formation in brain. These data indicate that the increased neuronal activity induced by centrally acting convulsants is likely to be the sole cause for the rise in cerebral prostaglandins. Brain hypoxia, another known stimulus of prostaglandin synthesis, does not seem to play an important role during convulsions.

Hipotese sobre o mecanismo de acao da homeopatia em funcao das recentes contribuicoes produzidas pela neurofisiologia / Hipothesys about the homeopathy action mode in view of the recent neurophysiology contributions

A evolucao das tecnicas de investigacoes biologicas permite apos alguns anos, a fisiologia, estudar as engrenagens mais delicadas celulares e sub-celulares. A este nivel, certos mecanismos de acao bem postos recentemente em evidencia pela neurofisiologia, permite entrever o mecanismo intimo de acao da homeopatia. Nos tomamos como exemplo a acao das doses homeopaticas do OPIUM e do STRYCHNINUM, comparando-as as recentes descobertas concernentes aos sistemas de neuromediacao endorfinica e glicinergica

Hipotese sobre o mecanismo de acao da homeopatia em funcao das recentes contribuicoes produzidas pela neurofisiologia / Hipothesys about the homeopathy action mode in view of the recent neurophysiology contributions

A evolucao das tecnicas de investigacoes biologicas permite apos alguns anos, a fisiologia, estudar as engrenagens mais delicadas celulares e sub-celulares. A este nivel, certos mecanismos de acao bem postos recentemente em evidencia pela neurofisiologia, permite entrever o mecanismo intimo de acao da homeopatia. Nos tomamos como exemplo a acao das doses homeopaticas do OPIUM e do STRYCHNINUM, comparando-as as recentes descobertas concernentes aos sistemas de neuromediacao endorfinica e glicinergica