Invertebrate Receptors

A voltage-gated sodium ion channel opens when there is a change in the voltage of the membrane and allows sodium ions to flow across its electrochemical gradient. These voltage-gated channels are made up of amino acids and they aid in generating and moving an action potential down a membrane or axon (Brooker, Robert, 106).

EDMAN KA & SCHILD HO 1962, ‘The need for calcium in the contractile response induced by acetylcholine

C ) (1) neurotransmitter released (2) diffused across the synaptic cleft to a receptor amino acid (3) binding of the transmitter opens pores in the ion channels and positive ions move in.

When substances like Acetylcholine (Ach) and norepinephrine which are small- molecular neurotransmitters are released into the body they bind to receptors on tissue or neurons through our ANS and PNS system. Ach is released by many PNS neurons and some CNS neurons. In the PNS Ach is an excitatory neurotransmitter at some synapses, such as the neuromuscular junction where it binds to ionotropic receptors which open cation channels. Ach can also be an inhibitory neurotransmitter at other synapses, where it binds to metabotropic receptors while opening potassium channels. The enzyme acetylcholinesterase (AchE) inactivates Ach by splitting into acetate and choline fragments. Norepinephrine (NE) is a biogenic amine; most biogenic amines may cause

It is expected that cholinergic receptors will be present. ACh has been shown to enhance the neurogenic heartbeat and the CG of crustaceans has been considered a cholinergic system (Yawaza 1992). Because DA has been found to be present in hemolymph and pericardial organs, it is suspected that there will be a presence dopaminergic receptors as well (Tierney

The most frequent inflammatory disease of the central nervous system (CNS) impacts the lives of two and half million people in the world, Multiple Sclerosis (MS) (Schattling, 2013). Growing up, this disease has personally affected my family, and seeing a first hand account of the burden and turmoil that this disease causes for all of its patients it is critical to understand how this disease degenerates neurons and axons. The key players in this process are nervous system ion channels that regulate the influx and efflux of sodium and calcium, whether through exchangers or voltage-gated channels. There are normal molecular settings in neurons and there are MS molecular settings; the two are very different and progressively become further

When both NA and Praz act on GPCR in VSM membrane, NA induces production of IP3 and Praz does not. Therefore, to produce same level of contraction from NA only by using NA with Praz, higher concentration of NA is necessary to occupy more receptor. Theoretically, the maximum (100%) concentration should be achieved with high concentration of agonist with antagonist (1 p10). 82.61% of contraction was observed in this experiment. it could be due to tissue damage from experimental process or could be influenced by more than five days storage of prepared tissue (3). 5HT2 receptor is located in the CNS and also located in the periphery (1 p196). The subtypes of 5HT2 are linked to colonic motility (5-HT2A), heart (5-HT2B), and central nervous system (5-HT2c) (1 p196). Meth act as antagonist to 5-HT2A, partial agonist to 5-HT2B, and antagonist to 5-HT2C (1 p199, 4). Both 5HT, and Meth works as agonist, but binding of 5HT to receptor give full response (full agonist), and Meth give less than full response (partial agonist). Meth act as agonist in presence of low concentration of 5HT with Meth. Meth act as antagonist in presence of high concentration of 5HT with Meth. Meth disturbs 5HT binding to receptor to give full response. Therefore, crossover of 5HT only trend line and 5HT with Meth should be observed. Absence of crossover might be due to different efficacies, as Meth is known

Ach binding to nicotinic receptors has an excitatory effect because it result in the direct opening of the Na channel and the production of action potential (VanPutte, Cinnamon L., and Rod R. Seeley). When Ach binds to The muscarinic receptor, the cell response is mediated through G proteins the response is either excitatory or inhibitory, depending on the effectors.( VanPutte, Cinnamon L., and Rod R. Seeley)

Gluconate is reported to have biological activities that are not related to its function as an anion substitute (Christoffersen and Skibsted, 1975). Therefore, we investigated the effect on electrical activity in mouse jejunal circular smooth muscle of replacing extracellular Cl- with isethionate, a different anion with low permeability through Cl- channels. Replacement of [Cl-]o with isethionate affected both membrane potential and slow wave properties. Application of 13.3 mM [Cl-]o, isethionate Krebs solution did not cause the transient effect on membrane potential in the first 40 s period after the solution change that was observed with the gluconate Krebs solution (Fig 2A). However, unlike gluconate, replacement of extracellular Cl- with isethionate did cause a significant depolarization of the membrane potential after the solution change (4-5 min) (Fig 3A, 4A; ∆Em, 13.3 mM [Cl-]o: 3.73 ± 1.06 mV; N=5; P < 0.05 vs. baseline; paired t test).

The muscarinic AChRs occur primarily in the CNS, and are part of a large family of G-protein-coupled receptors (‘G proteins’), which use an intracellular secondary messenger system involving an increase of intracellular calcium to transmit signals inside cells. Binding of acetylcholine to a muscarinic AChR causes a conformational change in the receptor that is responsible for its association with and activation of an intracellular G protein, the latter converting GTP to GDP in order to become activated and dissociate from the receptor. The activated G

In MG, the postsynaptic muscle membrane is distorted and simplified, having lost its normal folded shape, the concentration of acetylcholine receptors on the muscle

Two auxiliary beta subunits, together with a central alpha subunit make up a typical voltage-gated sodium channel (3). Anchoring of the channel to the membrane as well as traffic regulation in maintained by the beta subunit, whereas the alpha subunit provides the channel with stability to work as functional channel (1). The alpha subunit is compromised of four homologous domains (D1-D4)(1) and each domain consists of six alpha helical transmembrane segments (S1-S6)(3). The channel can be selective because of the poor loops between S5-S6 present in each domain. The transmembrane segment S4, in each domain, is able to act as a voltage sensor by holding amino acids that are positively charged (3). The diagram below shows a voltage gated sodium

The Ryanodine receptors (RyRs) are membrane proteins that are located in the sarcoplasmic and endoplasmic reticulum of the cells. The key role of the receptors is to mediate the release of calcium ions (Ca2+) from intracellular storages in either reticulum into the cytoplasm during excitation-contraction coupling in muscles. Intracellular Ca2+ regulation is important for secondary messenger for signal transduction and is essential for certain cellular processes. Ryanodine is named after the plant alkaloid ryanodine, which binds to the receptors and displays preferential interactions with the open state of the channel. At nanomole concentrations, they lock the Ca2+ channel in an open sub-conductance state and at higher concentration, they inhibit the channels completely. For mammalian organisms, there are three distinct RyRs are the largest known ion channels and three isoforms have been identified, RyR1, RyR2 and RyR3 each of which is encoded by a distinct gene on different chromosomes (Lanner, Georgiou, Joshi, &

TRPM2 channel have six putative transmembrane proteins with C-terminal and N-terminal (Figure 1; Fleig & Penner 2004; Jiang et al. 2010). TRPM2 channels form homomultimer (homotetramers), Yunjong Han, 997267443 ! 2 which have four subunits of six transmembrane proteins (S1 to S6, 24- transmembrane in

Background: Neuronal excitability mediated by sodium-dependent action potentials (APs) is required for rapid and specific communication in our brains. This underlies our ability to sense and respond to stimuli and for higher order cognitive functions including learning and memory. Voltage gated sodium channels (NaVs) open in response to membrane depolarization and initiate the AP. The α subunit is the major functional unit of NaVs and is comprised of 4 homologous domains (DI-DIV), each containing 6 transmembrane segments (S1-6)4,5. S4, the voltage sensor that detects depolarization, contains 4-8 positively charged amino acids each separated by two hydrophobic residues4,6. The positive charges on S4 are pushed outward by the electric field during membrane depolarization leading to channel opening, allowing influx of positively charged sodium ions down their concentration gradient4. Fast inactivation helps return the membrane to rest by blocking the conductance of sodium ions through the channel pore 1,2.