Secretion of acetylcholinesterase and butyrylcholinesterase from the guinea-pig isolated ileum

Lemon balm (Melissa officinalis L.) essential oil and citronellal modulate anxiety-related symptoms - In vitro and in vivo studies

ETHNOPHARMACOLOGICAL RELEVANCE

Besides psyche-related symptoms, patients with anxiety disorders can have a large number of somatic symptoms as well. Although the treatment of these disorders is mainly focused on resolving their mental component, one cannot neglect the need for the treatment of accompanying somatic symptoms. Melissa officinalis L. (lemon balm), in various formulations, has been extensively used as an ethnomedicinal remedy for the treatment of different psyche-related symptoms, and its use is considered relatively safe.

AIM OF THE STUDY

In the present study, the activity of M. officinalis (MO) essential oil was evaluated in several in vitro and in vivo models mimicking or involving anxiety-related somatic symptoms.

MATERIALS AND METHODS

To address the effect of MO essential oil on the gastrointestinal and heart-related symptoms accompanying anxiety disorders, in vitro models were utilized that follow the function of the isolated mouse ileum and atria tissues, respectively, after exposure to MO essential oil. Effects of MO essential oil on BALB/c mice motor activity was estimated using the open field, rota-rod, and horizontal wire tests. Additionally, the essential oil was assayed for its potential in inhibiting acetylcholinesterase activity.

RESULTS

The performance of mice treated with 25 mg/kg of the oil showed a statistically significant decrease in the motor impairment arising from acute anxiety (open field test), while there was a prolonged latency and a reduction of the frequency of falling from a rotating rod and/or a horizontal wire (signs of muscle weakness/spasms). Concentrations of the essential oil higher than 1 μg/mL were found to inhibit both spontaneous and induced ileum contractions. Moreover, the essential oil and citronellal were found to decrease isolated mouse atria contraction frequency, as well as contraction force. However, the oil was found to be a very weak acetylcholinesterase inhibitor.

CONCLUSION

The modulation of anxiety-related symptoms by the oil was found not to be mediated through the inhibition of the acetylcholinesterase, nonetheless, the mechanistic studies involving the ileum and cardiac tissues, revealed that the activity of MO and citronellal might be related to the modification of either voltage-gated Ca²⁺ channels or muscarinic receptors. Mice locomotion, balance, and muscle strength were not impacted by the essential oil; however, its main constituent, citronellal, was found to exert a certain degree of muscle function inhibition. All these results suggest that the activity of MO essential oil arises from synergistic and/or antagonistic interactions of its constituents, and is not completely dependent on the oil's main constituent.

Regulation of gastric electrical and mechanical activity by cholinesterases in mice

Background/Aims

Gastric peristalsis begins in the orad corpus and propagates to the pylorus. Directionality of peristalsis depends upon orderly generation and propagation of electrical slow waves and a frequency gradient between proximal and distal pacemakers. We sought to understand how chronotropic agonists affect coupling between corpus and antrum.

Methods

Electrophysiological and imaging techniques were used to investigate regulation of gastric slow wave frequency by muscarinic agonists in mice. We also investigated the expression and role of cholinesterases in regulating slow wave frequency and motor patterns in the stomach.

Results

Both acetycholinesterase (Ache) and butyrylcholine esterase (Bche) are expressed in gastric muscles and AChE is localized to varicose processes of motor neurons. Inhibition of AChE in the absence of stimulation increased slow wave frequency in corpus and throughout muscle strips containing corpus and antrum. CCh caused depolarization and increased slow wave frequency. Stimulation of cholinergic neurons increased slow wave frequency but did not cause depolarization. Neostigmine (1 μM) increased slow wave frequency, but uncoupling between corpus and antrum was not detected. Motility mapping of contractile activity in gastric muscles showed similar effects of enteric nerve stimulation on the frequency and propagation of slow waves, but neostigmine (> 1 μM) caused aberrant contractile frequency and propagation and ectopic pacemaking.

Conclusions

Our data show that slow wave uncoupling is difficult to assess with electrical recording from a single or double sites and suggest that efficient metabolism of ACh released from motor neurons is an extremely important regulator of slow wave frequency and propagation and gastric motility patterns.

Regional differences in neostigmine-induced contraction and relaxation of stomach from diabetic guinea pig

Delayed gastric emptying and autonomic neuropathy have been documented in patients with diabetes mellitus. Some medications used to treat delayed gastric emptying enhance release of acetylcholine from autonomic neurons to strengthen gastric contractions. Autonomic coordination among gastric regions may be altered in diabetes resulting in poor outcomes in response to prokinetic drugs. Fundus, antrum, and pylorus from STZ or control guinea pigs were treated with neostigmine to mimic release of acetylcholine from autonomic neurons by prokinetic agents. In diabetic animals, neostigmine-induced contractions were weaker in fundus and pylorus but similar in antrum. The muscarinic receptor antagonist 4-DAMP or the nicotinic receptor antagonist hexamethonium reduced neostigmine-induced contractions. Activation of presynaptic muscarinic receptors on nitrergic neurons was impaired in fundus and antrum from diabetic animals. Nerve-stimulated contractions and relaxations, number of nNOS myenteric neurons, and tissue choline content were reduced in fundus from diabetic animals. Despite reduced number of myenteric neurons, tissue choline content was increased in antrum from diabetic animals. Since cholinergic motility of each gastric region was affected differently by diabetes, prokinetic drugs that nondiscriminately enhance acetylcholine release from autonomic neurons may not effectively normalize delayed gastric emptying in patients with diabetes and more selective medications may be warranted.

Ion-channels on parasite muscle: pharmacology and physiology

Ion-channels are essential components of excitable cells. This fact has been exploited in the development of anthelmintic agents; the majority of which act on nematode ion channels. The purpose of this review is to describe the site of action of some frequently used anthelmintic compounds: nAChRs and levamisole/pyrantel; Glu-Cls and avermectins/mylbemycins; GABA receptors and piperazine. Also described is some of the physiological and pharmacological data on other nematode muscle ion-channels which may prove attractive targets for future anthelmintic development: Ca2+ activated Cl(-) channels; peptide gated chloride Cl(-) channels; Ca2+ channels and potassium channels. Emphasis is placed on the pharmacological and physiological data from parasite tissue. Information on the genes involved in ion-channel formation and modulation are reviewed in detail elsewhere in this issue.

In vitro Interactions Between the Oral Absorption Promoter, Sodium Caprate (C10) and S. typhimurium in Rat Intestinal Ileal Mucosae

PURPOSE

The medium chain fatty acid, sodium caprate (C(10)), is a promising oral drug delivery agent that may promote permeability of peptides through increasing paracellular permeability of the intestinal epithelium. One safety concern is that it may permit co-absorption of by-stander agents including pathogens. The purpose of this in vitro study was to examine the effects of C(10) on rat intestinal ileal mucosae in the presence of co-administered Salmonella typhimurium in a low volume vertical Ussing chamber.

METHODS

C(10) or S. typhimurium was added to rat ileal mucosae mounted in chambers and the flux of the paracellular flux of [(14)C]-mannitol examined. S. typhimurium adherence and uptake by ileal mucosae was also examined by counting. Bacterial growth curves were assessed in the presence of C(10). Minimum inhibitory- and bacteriocidal concentrations of C(10) were determined against a range of bacteria.

RESULTS

Apical addition of either C(10) or S. typhimurium to rat ileal mucosae mounted in modified diffusion chambers significantly increased the flux of [(14)C]-mannitol in a concentration-dependent fashion. Co-exposure with increasing concentrations of C(10) attenuated the Salmonella-induced increase in mannitol flux. Histological evaluation revealed that C(10) inhibited both adhesion and invasion of S. typhimurium to intestinal mucosae. Short term bacterial growth studies in the presence of C(10) showed evidence of concentration-dependent inhibition. C(10) was bacteriocidal in mM concentrations against S. typhimurium and selected gram positive and negative bacteria.

CONCLUSIONS

C(10) does not promote the permeation of a common bacterium across isolated intestinal tissue upon acute co-exposure. It prevents S. typhimurium attachment to epithelia and impedes growth of a range of different bacterial strains.

Parkinson's disease, Alzheimer's disease and motor neurone disease: identifying a common mechanism

Although Alzheimer's disease, Parkinson's disease, and motor neurone disease are distinct disorders, there could be a common neurodegenerative mechanism that characterises the death of selective neurone populations in each case. We propose that this mechanism could be an aberrantly activated, developmental process involving a non-classical, non-enzymatic action of acetylcholinesterase mediated via a short linear motif near the C-terminal end of the molecule. Since this motif has a highly conserved homology with part of the amyloid precursor protein, it may be particularly attractive as a target for novel therapeutic strategies in neurodegeneration.

Cholinoceptive neurons without acetylcholinesterase activity and enzyme-positive neurons without cholinergic synaptic innervation are present in the main olfactory bulb of adult rat

Light and electron microscopic histochemistry revealed acetylcholinesterase-positive and acetylcholinesterase-negative neurons in the main olfactory bulb of adult rat. Their distribution patterns on various neuron types have been analysed in detail. (1) No acetylcholinesterase staining could be demonstrated in the granule cells which receive a large number of the cholinergic synapses. (2) In contrast, enzyme activity was present in the soma and dendrites in most of the non-cholinergic and non-cholinoceptive relay cells (mitral cells and tufted cells) and in a subset of short-axon interneurons, where cholinergic synapses could not be detected. (3) Within the neuropil of glomeruli, two compartments were present, one of which was free of acetylcholinesterase-positive structures, while many enzyme-positive neuronal elements were seen in the other. (4) Characteristically, cholinergic and non-cholinergic neuronal structures showed triadic arrangements. (5) The axonal release of acetylcholinesterase from cholinergic axons is probable. It is suggested that, in the olfactory bulb, acetylcholinesterase is release by cholinergic afferent axons, and it is the cholinergic synapses that determine which postsynaptic neurons are cholinoceptive rather than the intraneuronal presence of acetylcholinesterase. In the main olfactory bulb, the acetylcholinesterase present in the relay cells therefore appears to have functions other than the hydrolysis of acetylcholine.

SCH 23390 equivalently, but YM-09151-2 differentially reduces the stimulant effects of methamphetamine, MK-801 and ketamine: assessment by discrete shuttle avoidance in mice

The inhibitory actions of the selective dopamine D1-and D2-antagonists SCH 23390 and YM-09151-2, respectively, on the mouse's discrete shuttle avoidance were almost equipotent at doses ranging from 0.01-0.1 mg/kg. SCH 23390 reduced the stimulant action of methamphetamine (0.5 mg/kg), MK-801 (0.1 mg/kg) and ketamine (10 mg/kg) with a similar potency. YM-09151-2 also antagonized the actions of these drugs, with the following order of effectiveness: ketamine > MK-801 > methamphetamine. The present results indicate that methamphetamine, MK-801 and ketamine have different characteristics of CNS stimulant action through dopamine D2-receptors.

Degradation of acetylcholine in human airways: role of butyrylcholinesterase

1. Neostigmine and BW284C51 induced concentration-dependent contractions in human isolated bronchial preparations whereas tetraisopropylpyrophosphoramide (iso-OMPA) was inactive on airway resting tone. 2. Neostigmine (0.1 microM) or iso-OMPA (100 microM) increased acetylcholine sensitivity in human isolated bronchial preparations but did not alter methacholine or carbachol concentration-effect curves. 3. In the presence of iso-OMPA (10 microM) the bronchial rings were more sensitive to neostigmine. The pD2 values were, control: 6.05 +/- 0.15 and treated: 6.91 +/- 0.14. 4. Neostigmine or iso-OMPA retarded the degradation of acetylcholine when this substrate was exogenously added to human isolated airways. A marked reduction of acetylcholine degradation was observed in the presence of both inhibitors. Exogenous butyrylcholine degradation was prevented by iso-OMPA (10 microM) but not by neostigmine (0.1 microM). 5. These results suggest the presence of butyrylcholinesterase activity in human bronchial muscle and this enzyme may co-regulate the degradation of acetylcholine in this tissue.

Presence of a soluble form of acetylcholinesterase in human ocular fluids

Samples of ocular fluid obtained from normal persons at necropsy and during eye surgery have been assayed for the presence of acetylcholinesterase. Measurable levels could be detected in all samples examined, but levels of acetylcholinesterase in vitreous humour were consistently higher than those in aqueous humour, indicating a possible retinal origin. Polyacrylamide gel electrophoresis revealed that the enzyme of ocular fluid had the same mobility as that of acetylcholinesterase from cerebrospinal fluid. It is probable that acetylcholinesterase is secreted from neuronal structures in the retina into the ocular fluid in an analogous manner to the secretion of acetylcholinesterase from brain neurones into cerebrospinal fluid.

Ratio of immunochemically determined amniotic fluid acetylcholinesterase to butyrylcholinesterase in the differential diagnosis of fetal abnormalities

A total of 111 amniotic fluid samples, clear or blood stained, with elevated levels of alpha-fetoprotein and acetylcholinesterase was analysed by immunoassays specific for acetylcholinesterase and butyrylcholinesterase and the acetylcholinesterase/butyrylcholinesterase-ratios determined. Samples from 40 pregnancies associated with anencephaly, 47 pregnancies associated with open spina bifida or encephalocele and six pregnancies with fetal intrauterine death or miscarriage all had ratios of greater than 0.14. All 11 pregnancies with fetal ventral wall defects had ratios less than 0.14 as had four pregnancies with normal outcome and elevated levels of alpha-fetoprotein and acetylcholinesterase. Three fetuses with both open spina bifida and ventral wall defects were associated with ratios above 0.14. These results suggest that immunochemical determination of acetylcholinesterase and butyrylcholinesterase can be used to distinguish pregnancies complicated by anencephaly, open spina bifida, encephalocele and miscarriage from those with ventral wall defects and samples with false positive elevated levels of alpha-fetoprotein and acetylcholinesterase. The procedure is accurate and simple to carry out and well suited to routine use in a clinical chemistry laboratory.

A novel water-soluble dopamine-2 antagonist with anticholinesterase activity in gastrointestinal motor activity. Comparison with domperidone and neostigmine

A novel water-soluble dopamine-2 antagonist, N-[4-[2-(dimethylamino) ethoxy]benzyl]-3,4-dimethoxybenzamide hydrochloride (HSR-803) was synthesized and assayed for its gastrointestinal smooth muscle stimulating activity in vivo and in vitro. In the in vivo study, gastrointestinal contractile activity was measured by means of chronically implanted force transducers in conscious dogs; it was found that HSR-803 at 3.0 mg/kg IV probably stimulated gastric contractile force twice during the digestive state and significantly antagonized dopamine-(1.0 mg/kg per hour) inhibited gastric contractions in doses of 0.3, 1, and 3 mg/kg IV. With a background IV infusion of HSR-803 at 3 mg/kg per hour, the contraction-stimulating activity of acetylcholine (0.05 mg/kg per minute) was greatly enhanced while the response to bethanechol was not changed. As a result, HSR-803 was found to have a strong anticholinesterase activity besides the antidopamine-2 activity; i.e., the anticholinesterase activity of HSR-803 at 3 mg/kg per hour was equivalent to that of neostigmine at 10 micrograms/kg per hour, and dopamine-2 antagonistic activity of HSR-803 was similar to that of domperidone on a weight basis. No symptom suggesting actions on the central nervous system was noticed in HSR-803 up to 10 mg/kg IV in conscious dogs. In the in vitro study, HSR-803 inhibited cholinesterase dose-dependently, and IC50 was 2.9 x 10(-6) mol/L, while those of neostigmine and domperidone were 2.3 x 10(-8) mol/L and 1.7 x 10(-5) mol/L, respectively. In conclusion, HSR-803 stimulates endogenous acetylcholine release by antagonizing the dopamine-2 receptor on the postsynaptic cholinergic neurons, and the anticholinesterase activity of HSR-803 may cause the released acetylcholine to accumulate at cholinergic receptor sites. Thus, HSR-803 is potentially capable of enhancing cholinergic activity in the gastrointestinal region.

GABA receptors on the somatic muscle cells of the parasitic nematode, Ascaris suum: stereoselectivity indicates similarity to a GABAA-type agonist recognition site

1. The gamma-aminobutyric acid (GABA) receptors on the somatic muscle cells of Ascaris, which mediate muscle cell hyperpolarization and relaxation, have been characterized by use of intracellular recording techniques. 2. These receptors are like mammalian GABAA-receptors in that the response is mediated by an increase conductance to chloride ions. The GABAA-mimetic, muscimol, has a relative potency of 0.40 +/- 0.02 (n = 3) compared to GABA. 3. The stereoselectivity of the GABA receptor on Ascaris is identical to that for the mammalian GABAA-receptor, as determined from the relative potency of three pairs of enantiomers of structural analogues of GABA. 4. The most potent agonist is (S)-(+)-dihydromuscimol which is 7.53 +/- 0.98 (n = 5) times more potent than GABA. 5. The Ascaris GABA receptor is not significantly blocked, at concentrations below 100 microM by the potent, competitive GABAA-receptor antagonist, SR95531. 6. The Ascaris GABA receptor does not recognise agents that are known to block the GABA gated chloride channel in mammalian preparations such as t-butylbicyclophosphorothionate (TBPS, 10 microM, n = 2) or the insecticide dieldrin (100 microM, n = 3). 7. GABAergic responses in Ascaris are not potentiated by pentobarbitone (100 microM, n = 3) or flurazepam (100 microM, n = 3). 8. The potencies of various GABA-mimetics in the Ascaris preparation have been compared with their potency at displacing GABAA-receptor binding in mammalian brain. Excluding the sulphonic acid derivatives of GABA, the correlation coefficient (r) between the potencies of compounds in the two systems is 0.74 (P less than 0.01). The significance of this correlation is discussed. 9. The pharmacology of the Ascaris GABA receptor is discussed in relation to other invertebrate systems and the mammalian subclassification of GABA receptors.