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Synthesized in the endoplasmic reticulum, a fraction of the subunits of this receptor assemble into homo and hetero-pentameric complexes. The only complexes that reach the cell surface, after exiting from endoplasmic reticulum are the pentameric complexes. nAChRs have been identified as crucial elements in central nervous system functions such as consciousness, attention, and memory; and participate in numerous cerebral circuits. (Bocquet, Carvalho, Cartaud, Neyton Poupon, Taly, Grutter, Changeux, Corringer 2007)
The opening of the channels of these receptors is triggered by the neurotransmitter acetylcholine. Nicotine also has the same effect. A diagram of the chemical structure of acetylcholine is given below.
Nicotinic acetylcholine receptors are located mainly in the postsynaptic membrane under the motor nerve terminal at the neuromuscular junction. Nicotinic receptors can also be found in different synaptic locations; e.g. the muscle nicotinic receptor always functions post-synaptically. The nerve cell forms of the receptor can be found both post-synaptically (performing classical neurotransmission) and pre-synaptically (causing the release of other neurotransmitters). In contrast to the muscarinic acetylcholine receptors, Nicotinic Acetylcholine receptors do not operate with the help of a second messenger. Instead they open themselves forming an ion channel. Curare causes inhibition of these receptors.
Nicotinic acetylcholine receptors have a very wide distribution in the various body tissues. Nerve cell receptors are found in the central nervous system and also in the peripheral nervous system. The neuromuscular receptors, on the other hand are found in the neuromuscular junctions of somatic muscles.
The neuromuscular receptors, on the other hand are found in the neuromuscular junctions of somatic muscles. The stimulation of these receptors causes muscular contraction.(Barrantes 1998)
Structure and function of Nicotinic Acetylcholine Receptors
The nicotinic acetylcholine receptor protein includes one or many sites which can bind the neurotransmitter ACh and also a specific channel for cat ions which is also known as the intrinsic cationic channel. These ions can be Na+, Ca2+ or K+ and the channel is specific in nature. The process of the opening of ion channel is linked to the binding of ACh. (Maelicke 1986)
Protein chemistry and sequence analysis of polypeptide has revealed a general scheme for each subunit which consists of :
1. A globular extra cellular N-terminal domain (ECD);
2. A trans-membrane domain (TMD)
3. A cytoplasmic domain
There are 2 to 5 Acetylcholine binding sites on the ECD. Nicotinic receptors have many subunits and these subunits belong There are 2 to 5 Acetylcholine binding sites on the ECD. Nicotinic receptors have many subunits and these subunits fit in a multigene family (seventeen members in the human being) When many of the subunits combine they form a great numbers of receptors. Every subunit gives three parts or "loops" to the site of binding. The sites which bind ACh are located on the outer side of the subunits. And as the agonist binds, the subunits happen to be more alike to the other subunits. And the channel gets more proportioned and a hole of about 0.65nm in diameter opens up. This channel helps the nicotinic acetylcholine receptor to adhere to its role by many ways. Firstly it encloses a mechanism of gating which is closed in the inactive states of the channel but it is open in the active
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The effect of Salbutamol on the response of Ileum to Acetylcholine Response to question 1. From the graph, the EC50 of Acetylcholine is 4.00E-08, while the EC50 of Salbutamol + Acetylchline is 4.00E-08. The values for the Ec50 of Nicotine are 5.5E-06, and the EC50 OF Salbutamol + Nicotine is 5.00E-06.
This does not though support smoking of nicotine especially due to the fact that it normally has some undesirable effects on the body. Nicotine normally activates all the neural nicotinic receptor types including the ones which cause side effects. Therefore by designing novel nicotinic drugs that interact selectively with some types of neuronal nicotinic receptors but not all it is quite possible to hit only those receptors that are relevant to the given disease (Rennard, 2008).
nAChRs have essential physiological roles in the central and peripheral nervous systems that depend on the subunit composition and are considered to be primary mediators of nicotine addiction (Walsh, H. et al., 2008). An acceptable strategy for pharmacological intervention in nicotine dependence would be the use of a drug with partial agonist properties at nicotinic receptors (Clementi et al., 2000).
With the potato-killing fungus the starvation and connected health problems death toll reached one million, which was one eighth of the total population. O'grada, in his famous work, argues that a large number of these pathetic deaths could have been prevented with a less doctrinaire attitude to the famine relief.
The noncompetitive antagonism of a number of clinically useful drugs has been attributed to binding within the central lumen of the nAChRs. NCA activity has been routinely determined by measurement of concentration-dependent effects on whole-cell currents or nicotine-induced 86RB+ influx, yielding IC50 values.
Recently smoking has received increased attention as was noted by the approval of bupropion to treat smoking in 1997 under the name Zyban. The latest product to be approved for smoking cessation is Chantix (varenicline tartrate) from Pfizer Inc. It has been shown to be a considerable improvement over Zyban.
While the individual patient, rather than his or her disease, is the appropriate focus of treatment for substance abuse, an understanding of the neurobiology of dependence and addiction can clarify the rationales for treatment methods and goals. Brain abnormalities resulting from chronic use of nicotine, stimulants (e.g., cocaine), opioids, cannabis, alcohol, hallucinogens (e.g., phencyclidine), inhalants (e.g., toluene), and many other abused substances are underlying causes of dependence and addiction meaning intense substance craving and compulsive use.
This response creates relaxation in the paralysis condition. They do not cross the blood brain barrier, so they do not act on the Central Nervous System. (Aschenbrenner and Venable 2008).
There are two major types of
Nicotine is responsible in the modulation of neurotransmitters release through the presynaptic activation. The many behavioural and physiological influences of nicotine could lead to the release of a variety of neurotransmitters through the activation of
Nucleus is contained in the cell body. In terms of its physiology, dendrites carry various impulses away from its nucleus while axons vice versa. Those neurons with myelin sheath often conduct impulses faster
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