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At least 163 records · Page 9Linked to original sources
PubMed1997

Effects of 3,3-dipyridylmethyl-1-phenyl-2-indolinone on gamma-aminobutyric acid elicited chloride current of snail central neuron.

The effects of (1) gamma-aminobutyric acid (GABA) on the excitable membrane and (2) DPMPI (3,3-dipyridylmethyl-1-phenyl-2-indolinone) on the microperfused GABA elicited currents were investigated on central LP5 neuron of giant African snail, Achatina fulica Ferussac, with conventional voltage-clamp technique. GABA elicited an inward current of LP5 neuron by a concentration and voltage dependent manner. Muscimol, GABAA receptor agonist, did, while baclofen, GABAB receptor agonist, did not, elicit the membrane current on the neuron. The GABA elicited currents in LP5 neuron were blocked by picrotoxin, a GABAA receptor ion channel complex antagonist while the currents were not blocked by phaclofen, a GABAB receptor antagonist. The results suggested that the GABA elicited current in LP5 neuron was mainly due to activation of GABAA receptor. DPMPI increased the frequency of the spontaneously generated action potential of the neuron. In the voltage clamped neuron, DPMPI decreased the GABA elicited responses by a concentration dependent manner. DPMPI altered neither the reversal potential of GABA elicited current, nor the membrane resistance of the excitable membrane of central LP5 neuron. The results concluded that DPMPI altered the GABAA activated receptor ionic channel complex of the LP5 neuron.

Action Potentials↗
PubMed1995

Mutation of an arginine residue in the human glycine receptor transforms beta-alanine and taurine from agonists into competitive antagonists.

Agonist binding to the inhibitory glycine receptor (GlyR) initiates the opening of a chloride-selective channel that modulates the neuronal membrane potential. Point mutations of the GlyR, substituting Arg-271 with either Leu or Gln, have been shown to underlie the inherited neurological disorder startle disease (hyperekplexia). We show that these substitutions result in the redistribution of GlyR single-channel conductances to lower conductance levels. Additionally, the binding of the glycinergic agonists beta-alanine and taurine to mutated GlyRs does not initiate a chloride current, but instead competitively antagonizes currents activated by glycine. These findings are consistent with mutations of Arg-271 resulting in the uncoupling of the agonist binding process from the channel activation mechanism of the receptor.

Arginine↗
PubMed1997

Allosteric modulation by single enantiomers of a C3-chiral 1,4-benzodiazepine of the gamma aminobutyric acid type A receptor channel expressed in Xenopus oocytes.

Xenopus laevis oocytes injected with Poly(A)(+)-RNA isolated from neuronal tissue express membrane proteins peculiar to the origin of mRNA. The translation of gamma aminobutyric acid type A (GABAA) receptors has been shown by dose/ response behavior of GABA and the reversible blockade of the GABA-induced current by picrotoxin. This current was analyzed quantitatively under two electrode voltage-clamp conditions. This methodology has been applied for the first time to study the functional properties of the receptor as a function of the stereochemistry of the ligands. The (+)-S and (-)-R enantiomers of a water-soluble benzodiazepine derivative, 7-chloro-1,3-dihydro-3-hemisuccinyloxy-5-phenyl-1,4-benzodiazep in-2-one (OXHEM), obtained by preparative high performance liquid chromatographic (HPLC) resolution on chiral stationary phase, act as agonists in the in vitro modulation of the chloride channel. The (+)-S-OXHEM enantiomer was the more active.

Animals↗
PubMed1988

Prolactin synthesis in cultured pituitary cells is chloride-dependent.

Release of prolactin from both normal pituitary cells and rat pituitary tumor (GH) cells is an osmotic process that is dependent upon chloride. The long term growth rate of GH-cells in medium in which chloride was exchanged with isethionate was completely normal, but, by 48 h, isethionate substitution resulted in a 70% decrease in the concentration of internal and secreted prolactin. Isethionate caused a much smaller reduction in growth hormone production (less than 20%). These results suggest that exchange of chloride with isethionate is inhibiting the synthesis of prolactin. Reduction of intracellular levels of prolactin in cells grown in isethionate-containing medium was evident by 30 h, and the level of prolactin was reduced 92% at 96 h. This reduction in the internal concentrations of prolactin was reversed when the cells were returned to normal medium containing chloride with a t1/2 of 48 h. Addition of epidermal growth factor and the calcium channel agonist BAY K 8644 to cells in medium containing chloride increased internal prolactin by 400%, and isethionate exchange reduced the response by 85%. To confirm that isethionate exchange was inhibiting the synthesis of prolactin, mRNA concentrations for prolactin and actin were determined. Both basal and hormone-stimulated levels of prolactin mRNA were reduced 70 to 90% by isethionate exchange, while actin mRNA levels did not change. To determine whether the effect of isethionate was at the level of gene transcription, GH-cells were transfected with a prolactin-chloramphenicol acetyltransferase fusion gene and chloramphenicol acetyltransferase expression was assessed using cells in chloride and isethionate-containing media. Both basal and hormone-stimulated synthesis of chloramphenicol acetyltransferase driven by the prolactin promoter was inhibited by isethionate exchange. These studies demonstrate that exchange of medium chloride with isethionate inhibits the synthesis of prolactin at the level of transcription.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1995

Channel gating in the absence of agonist by a homo-oligomeric molluscan GABA receptor expressed in Xenopus oocytes from a cloned cDNA.

We have previously described the isolation of a complementary DNA (cDNA) from the freshwater mollusc Lymnaea stagnalis encoding a polypeptide that exhibits approximately 50% identity to the beta-subunits of vertebrate gamma-aminobutyric acid (GABA) type A (GABAA) receptor. When expressed in Xenopus laevis oocytes from in vitro-transcribed RNA, the snail subunit forms functional homo-oligomeric receptors possessing chloride-selective ion channels. In recordings from voltage-clamped oocytes held at -60 mV, GABA induced an inward current, whereas application of the chloride-channel blocker picrotoxin (in the absence of agonist) elicited an apparent outward current. Single channel recordings obtained from cell-attached patches have revealed a single population of approximately 20 pS channels, with an open probability greater than 90% (at a pipette potential of -100 mV) in the absence of GABA. The relationship between single channel current and pipette potential was linear over the studied range (-100 mV to +60 mV), but the open probability was less for hyperpolarizations than for depolarizations. The spontaneous channel openings were blocked by micromolar concentrations of picrotoxin. Functional hetero-oligomeric receptors were formed when the molluscan subunit was co-expressed in oocytes with the bovine GABAA receptor alpha 1-subunit, but the channels gated by these receptors did not open spontaneously.

Animals↗
PubMed1991

GABA accelerates excitotoxic cell death in cortical cultures: protection by blockers of GABA-gated chloride channels.

The effects of gamma-aminobutyric acid (GABA) and related agonists and antagonists on the excitatory cell death were examined in dispersed primary cultures of the rat cerebral cortex. The cytotoxic effects evoked by kainic acid, quisqualic acid and N-methyl-D-aspartic acid were evaluated by phase contrast microscopy and quantified by the measurement of lactic dehydrogenase release into the culture medium. GABA accelerated the cell death in a concentration-dependent fashion, but did not influence the amount of cells dying with 24 h after the treatment. This effect of GABA could be mimicked by GABAA rather than GABAB receptor agonists. Blockers acting at different sites of the GABAA receptor/chloride channel complex not only reduced the GABA-induced acceleration of cell death, but also showed a significant protection against the excitotoxic cell death in the absence of exogenous GABA. Blockers of chloride channels unrelated to GABA receptors produced similar protection. Our findings indicate that GABA-gated chloride channels may be effective in modulating excitotoxic vulnerability of cerebrocortical cells.

Animals↗
PubMed2000

Modification of a weak learning experience by memory retrieval in the day-old chick.

Activation of memory retrieval after weak learning (WL), during either the short- or intermediate-term stages of memory in day-old chickens, resulted in the strengthening of the memory to levels normally associated with strong learning. Administration of the calcium channel antagonist lanthanum chloride, the glutamate receptor agonist monosodium glutamate, or the N-methyl-D-aspartate glutamatergic receptor antagonist AP5 prevented strengthening of a WL memory by reminder-activated memory retrieval. The results of this study are discussed in light of our recent findings suggesting two phases of memory retrieval in the day-old chick. The results are consistent with the proposition that a memory undergoing the processes of formation may be modified to include information gleaned at the time of memory retrieval and that a second phase of memory retrieval may be responsible for such modification.

2-Amino-5-phosphonovalerate↗
PubMed1996

The differential antagonism by bicuculline and SR95531 of pentobarbitone-induced currents in cultured hippocampal neurons.

In voltage clamped cultured hippocampal neurons, application of gamma-aminobutyric acid (GABA) or pentobarbitone induced chloride current in a dose-dependent manner. The dose dependence of these agonists were well described by ED50 and Hill coefficients of 14.7 +/- 7 microM and 1.2 +/- 0.5, and 299 +/- 17.3 microM and 1.6 +/- 0.1, for GABA and pentobarbitone, respectively. The effects of two GABAA receptor antagonists, bicuculline and 2-(3-carboxypropyl)-3-amino-6-methoxyphenyl-pyridazinium bromide (SR95531) were evaluated by co-application of increasing concentrations of the antagonists with a fixed equipotent (approximately ED30) dose of GABA or pentobarbitone. Both bicuculline and SR95531 blocked the GABA induced current with ID50 and Hill coefficients of 0.74 +/- 0.07 microM and 0.96 +/- 0.07, and 0.44 +/- 0.02 microM and 1.22 +/- 0.06, respectively. Bicuculline similarly blocked the pentobarbitone induced current with a ID50 and Hill coefficient of 0.69 +/- 0.04 microM and 1.2 +/- 0.1. However, pentobarbitone induced current was poorly blocked by SR95531 retaining 86.5% of current amplitude at a concentration of SR95531, 200 times the IC50 for GABA induced current. Current induced by etomidate, another intravenous general anesthetic with GABAA receptor agonistic property, is likewise resistant to SR95531 blockade. Three-dimensional modeling of bicuculline and SR95531 with alignment of the molecules along the suggested GABA-receptor binding moiety indicates that these two antagonist molecules have distinct steric properties. We suggest that GABA and pentobarbitone act at nearby but non-identical sites on the hippocampal GABAA receptor to open the chloride ionophore, and that these sites can be distinguished by bicuculline and SR95531. This is the first demonstration that the prototypic GABAA site antagonists bicuculline and SR95531 have different effects on currents induced by GABA and pentobarbitone.

Anesthetics, General↗
PubMed2000

Role of Ca2+- and swelling-activated Cl- channels in alpha1-adrenoceptor-mediated tone in pressurized rabbit mesenteric arterioles.

BACKGROUND: Ca2+-activated (I(Cl(Ca))) and swelling-induced (I(Cl(swell))) Cl- channels have, respectively, been postulated to participate in the membrane depolarization and contraction mediated by activation of alpha1-adrenoceptors and vascular wall distension during pressurization. Their respective function in generating active force in pressurized arterioles during alpha1-adrenoceptor stimulation remains unsettled. OBJECTIVES: Experimental protocols were designed to: (1) assess the relative contribution of I(Cl(Ca)) to the pressure-dependence of lumen diameter of mesenteric arterioles at different states of activation of the alpha1-adrenoceptor, and (2) investigate the potential role of I(Cl(swell)) in spontaneous and agonist-mediated myogenic reactivity. METHODS: Segments of endothelium-denuded rabbit mesenteric arterioles with a lumen diameter of approximately 70 microm were cannulated at both ends and studied under isobaric conditions at 36 degrees C. Steady-state lumen diameter at each pressure step investigated (0-100 mmHg, in 20-mmHg increments) was measured by a video-microscopy edge-detection technique. RESULTS: Under control conditions, 23% of the arterioles developed nifedipine-sensitive spontaneous myogenic tone. In the presence of 1 mM tetraethylammonium chloride (TEA) to inhibit Ca2+-dependent K+ channels, the alpha1-agonist phenylephrine (PE) contracted the vessels in a concentration-dependent manner (0.1-10 microM) and potentiated myogenic reactivity. The contraction mediated by 1 microM PE/TEA was abolished by 1 microM nifedipine, indicating that Ca2+ entry through voltage-gated Ca2+ channels was a necessary step in the cascade leading to contraction. Niflumic acid (NfA, 100 microM), a relatively selective inhibitor of I(Cl(Ca)), had no effect on myogenic tone but reversed the PE-induced contraction, varying with the concentration of PE and transmural pressure. For PE concentrations between 0.1 and 1 microM, but not for 10 microM PE, the relaxing efficacy of NfA decreased as applied pressure was raised from 0 to 100 mmHg. At all pressure steps, the NfA-induced relaxation was inversely related to the concentration of PE. DIDS (200 microM), another Cl- channel blocker, inhibited spontaneous myogenic tone, and partially suppressed a component of contraction at elevated transmural pressures in arterioles incubated in 1 microM PE/1 mM TEA/100 microM NfA. CONCLUSIONS: Our data indicate that under low to moderate stimulation of the alpha1-adrenoceptor signaling pathway, I(Cl(Ca)) channels play an important role in the sustained contraction produced. Their declining contribution to contraction with increasing transmural pressure may be explained, at least in part, by a progressive enhancement of stretch-induced ionic conductances, possibly volume-sensitive Cl- channels.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1995

The low efficacy gamma-aminobutyric acid type A agonist 5-(4-piperidyl)isoxazol-3-ol opens brief Cl- channels in embryonic rat olfactory bulb neurons.

4-PIOL is a structural analog of GABA that has low efficacy at GABAA receptor CI- channels and activates a nondesensitizing CI- conductance in central neurons. We investigated the biophysical mechanisms of its low efficacy in embryonic olfactory bulb neurons, which express a limited number of GABAA receptor subunit transcripts. Spectral analysis of GABA- and 4-PIOL-induced current fluctuations evoked in whole-cell recordings showed that three components with mean durations of approximately 0.7, 5, and 50 msec adequately describe the kinetics of the responses induced by both ligands. The contribution of the longest-lasting component was approximately 60% in the spectra of GABA-evoked responses but < 3% in the spectra of 4-PIOL-evoked responses. This is interpreted as a low incidence of long-lasting bursts in 4-PIOL-evoked responses. No difference was evident between the average inferred unitary conductances for 4-PIOL- and GABA-induced channels. These results at the level of the whole cell were confirmed and extended in outside-out single channel recordings. Taken together, the results indicate that the mechanism responsible for the low efficacy of 4-PIOL is the inability to produce frequent bursts of long duration.

Animals↗
PubMed1996

An amino acid substitution in the pore region of a glutamate-gated chloride channel enables the coupling of ligand binding to channel gating.

Many of the subunits of ligand-gated ion channels respond poorly, if at all, when expressed as homomeric channels in Xenopus oocytes. This lack of a ligand response has been thought to result from poor surface expression, poor assembly, or lack of an agonist binding domain. The Caenorhabditis elegans glutamate-gated chloride channel subunit GluClbeta responds to glutamate as a homomeric channel while the GluClalpha subunit is insensitive. A chimera between GluClalpha and GluClbeta was used to suggest that major determinants for glutamate binding are present on the GluClalpha N terminus. Amino acid substitutions in the presumed pore of GluClalpha conferred direct glutamate gating indicating that GluClalpha is deficient in coupling of ligand binding to channel gating. Heteromeric channels of GluClalpha+beta may differ from the prototypic muscle nicotinic acetylcholine receptor in that they have the potential to bind ligand to all of the subunits forming the channel.

Amino Acid Sequence↗
PubMed2001

The biochemical basis of anthelmintic action and resistance.

The most commonly used modern anthelmintics include the benzimidazoles, the nicotinic agonists. praziquantel, triclabendazole and the macrocyclic lactones. These drugs interfere with target sites that are either unique to the parasite or differ in their structural features from those of the homologous counterpart present in the vertebrate host. The benzimidazoles exert their effect by binding selectively and with high affinity to the beta-subunit of helminth microtubule protein. The target site of the nicotinic agonists (e.g. levamisole, tetrahydropyrimidines) is a pharmacologically distinct nicotinic acetylcholine receptor channel in nematodes. The macrocyclic lactones (e.g. ivermectin, moxidectin) act as agonists of a family of invertebrate-specific inhibitory chloride channels that are activated by glutamic acid. The primary mode of action of other important anthelmintics (e.g. praziquantel, triclabendazole) is unknown. Anthelmintic resistance is wide-spread and a serious threat to effective control of helminth infections, especially in the veterinary area. The biochemical and genetic mechanisms underlying anthelmintic resistance are not well understood, but appear to be complex and vary among different helminth species and even isolates. The major mechanisms helminths use to acquire drug resistance appear to be through receptor loss or decrease of the target site affinity for the drug. Knowledge on the mechanisms of drug action and resistance may be exploitable for the development of new drugs and may provide information on ways to overcome parasite resistance, respectively.

Animals↗
PubMed2004

Comparison of taurine- and glycine-induced conformational changes in the M2-M3 domain of the glycine receptor.

In the ionotropic glutamate receptor, the global conformational changes induced by partial agonists are smaller than those induced by full agonists. However, in the pentameric ligand-gated ion channel receptor family, the structural basis of partial agonism is not understood. This study investigated whether full and partial agonists induce different conformation changes in the glycine receptor chloride channel (GlyR). A substituted cysteine accessibility analysis demonstrated previously that glycine binding induced an increase in surface accessibility of all residues from Arg(271) to Lys(276) in the M2-M3 domain of the homomeric alpha1 GlyR. Here we compare the surface accessibility changes induced by the full agonist, glycine, and the partial agonist, taurine. In GlyRs incorporating the A272C, S273C, L274C, or P275C mutation, the reaction rate of the cysteine-specific compound, methanethiosulfonate ethyltrimethylammonium, depended on how strongly the receptors were activated but was agonist-independent. Reaction rates could not be compared in the R271C and K276C mutant GlyRs because methanethiosulfonate ethyltrimethylammonium did not modify the extremely small currents induced by saturating taurine or equivalent low glycine concentrations. The results indicate that bound taurine and glycine molecules impose identical conformational changes to the M2-M3 domain. We therefore conclude that the higher efficacy of glycine is due to an increased ability to stabilize a common activated configuration.

Arginine↗
PubMed1995

Ion transport in primary cultures from human sweat gland coils studied with X-ray microanalysis.

Chloride secretion in primary cultures of cells originating from the secretory coil of human sweat glands was investigated by electron probe X-ray microanalysis. The total intracellular Cl concentration was lowered by muscarinic agonists (carbachol and acetylcholine), as well as by the calcium ionophore A23187. The muscarinic agonists also lowered the cellular K concentration. Cl- secretion induced by these agonists could be inhibited by the chloride channel blocker NPPB. After cAMP stimulation, the frequency distribution of the Cl concentration changed from Gaussian to bimodal, indicating that cAMP induces Cl- secretion only from a subpopulation of the cells. Also ATP stimulated Cl- secretion, indicating the presence of purinergic receptors. The results suggest that some of the cells in addition to Ca(2+)-regulated Cl- channels also possess cAMP-activated Cl- channels. Hence, the primary cultures still possess the Cl- transport mechanisms known to be present in intact glands. It can, however, not be excluded that some coil cells have acquired ductal characteristics during culture.

Adenosine Triphosphate↗
PubMed1987

Proconflict and electrocorticographic effects of drugs modulating GABAergic neurotransmission.

Proconflict and electrocorticographic effects of drugs acting on the benzodiazepine (BDZ)/GABA/chloride-ionophore receptor complex were studied in rats in an attempt to correlate their anxiogenic and epileptogenic activities. Evidence for proconflict activity was assessed by means of an operant conflict procedure based on the simultaneous reward and punishment of a conditioned task, while epileptogenic properties were assessed by monitoring the electrocorticogram (ECoG) of free-moving rats. Pentylenetetrazole and picrotoxin, which act through a site on the chloride channel, and the benzodiazepine (BDZ) inverse agonist FG 7142 showed epileptogenic alterations in the ECoG at doses, respectively, 8, 2 and 3 times higher than those eliciting a significant proconflict effect. For the partial inverse agonist CGS 8216, a ratio of about 60 was found while the BDZ antagonist Ro 15-1788 showed neither epileptogenic nor proconflict activity, except at the highest tested dose for the latter effect (40 mg X kg-1 PO). Inhibition of GABA transmission may mediate both anxiogenic and epileptogenic actions, and a link between these properties may exist as a continuous spectrum of negative intrinsic efficacy at the central BDZ/GABA/chloride-ionophore receptor complex.

Animals↗
PubMed1999

Effects of the chlorotriazine herbicide, cyanazine, on GABA(A) receptors in cortical tissue from rat brain.

Chlorotriazine herbicides disrupt luteinizing hormone (LH) release in female rats following in vivo exposure. Although the mechanism of action is unknown, significant evidence suggests that inhibition of LH release by chlorotriazines may be mediated by effects in the central nervous system. GABA(A) receptors are important for neuronal regulation of gonadotropin releasing hormone and LH release. The ability of chlorotriazine herbicides to interact with GABA(A) receptors was examined by measuring their effects on [3H]muscimol, [3H]Ro15-4513 and [35S]tert-butylbicyclophosphorothionate (TBPS) binding to rat cortical membranes. Cyanazine (1-400 microM) inhibited [3H]Ro15-4513 binding with an IC50 of approximately 105 microM (n=4). Atrazine (1-400 microM) also inhibited [3H]Ro15-4513 binding, but was less potent than cyanazine (IC50 = 305 microM). However, the chlorotriazine metabolites diaminochlorotriazine, 2-amino-4-chloro-6-ethylamino-s-triazine and 2-amino-4-chloro-6-isopropylamino-s-triazine were without significant effect on [3H]Ro15-4513 binding. Cyanazine and the other chlorotriazines were without effect on [3H]muscimol or [35S]TBPS binding. To examine whether cyanazine altered GABA(A) receptor function, GABA-stimulated 36Cl- flux into synaptoneurosomes was examined. Cyanazine (50-100 microM) alone did not significantly decrease GABA-stimulated 36Cl- flux. Diazepam (10 microM) and pentobarbital (100 microM) potentiated GABA-stimulated 36Cl- flux to 126 and 166% of control, respectively. At concentrations of 50 and 100 microM, cyanazine decreased potentiation by diazepam to 112 and 97% of control, respectively, and decreased potentiation by pentobarbital to 158 and 137% of control (n = 6). Interestingly, at lower concentrations (5 microM), cyanazine shifted the EC50 for GABA-stimulated 36Cl- flux into synaptoneurosomes from 28.9 to 19.4 microM, respectively (n = 5). These results suggest that cyanazine modulates benzodiazepine, but not the muscimol (GABA receptor site) or TBPS (Cl- channel), binding sites on GABA(A) receptors. Furthermore, at low concentrations, cyanazine may slightly enhance function of GABA(A) receptors, but at higher concentrations, cyanazine antagonizes GABA(A) receptor function and in particular antagonizes the positive modulatory effects of diazepam and pentobarbital.

Animals↗
PubMed2000

Anthelmintic actions on homomer-forming nicotinic acetylcholine receptor subunits: chicken alpha7 and ACR-16 from the nematode Caenorhabditis elegans.

Two homomer-forming nicotinic acetylcholine receptor subunits with 47% identity in their amino acid sequences were employed to compare the actions of cholinergic anthelmintics and ivermectin on expressed vertebrate and nematode nicotinic receptors of known molecular composition. Voltage-clamp electrophysiology was used to study recombinant nicotinic receptors expressed in Xenopus laevis oocytes following nuclear injection of cDNA encoding either chicken alpha7 or Caenorhabditis elegans ACR-16 (Ce21) subunits. Butamisole, morantel and metyridine were without agonist actions on either alpha7 or ACR-16 nicotinic receptors in the range 10nM-1mM. However, butamisole (pIC(50)=4.9 for both alpha7 and ACR-16) and morantel (pIC(50)=5.6 for alpha7 and 5.7 for ACR-16) antagonized responses of both alpha7 and ACR-16 receptors to acetylcholine. Metyridine (1mM) did not affect responses to acetylcholine of either receptor. Oxantel was without agonist actions on ACR-16, but was an acetylcholine antagonist (pIC(50)=5.4). In contrast, it was found to have low efficacy agonist action (pEC(50)=4.4) on alpha7 at concentrations in the range 10-300microM. In agreement with a previous study, ivermectin (30microM), an agonist of L-glutamate-gated chloride channels, enhanced the amplitude of responses to acetylcholine of alpha7 nicotinic receptors. However, this same concentration of ivermectin (30microM) did not potentiate the acetylcholine-induced responses of ACR-16, but rather resulted in a slight attenuation. We conclude that oxantel and ivermectin have identified new pharmacological differences between the chicken alpha7 nicotinic receptor and its C. elegans homologue ACR-16.

Acetylcholine↗