Nerve transmission

Lindane is used predominately as a seed dressing and soil insecticide, for the control of ectoparasites of humans and domestic animals, for the control of locusts and grasshoppers, and as a residual spray to control the Anopheles vectors of malaria. Because of its relatively high volatility it is useful to control wood-boring insects of timber, fmit trees, and ornamental plants. The mode of action is not well understood but is thought to be competitive blocking of the y-aminobutyric acid (GABA) transmitter of synaptic nerve transmission. 

A number of quaternary amines are effective at modulating nerve transmissions. They often have the disadvantage of being relatively nonselective and so possess numerous sideeffects. This contrasts with the advantage that they do not cross the blood-brain barrier and so have no central sideeffects. Clo-... 

Acetylcholine Nerve transmission (neuromuscular activates cation channels... 

Histamine also induces antinociceptive (i.e. pain-relieving) responses in animals after microinjection into several brain regions [73, 74]. H, and H2 mechanisms are significant and both neuronal and humoral mechanisms may be involved. Brain H2 receptors appear to mediate some forms of endogenous analgesic responses, especially those elicited by exposure to stressors [75]. Many of the modulatory actions of histamine discussed above appear to be activated as part of stress responses. For reasons that remain unclear, histamine releasers, such as thioperamide, show only mild, biphasic antinociceptive actions, even though histamine is a potent and effective analgesic substance. Outside the brain, both H and H3 receptors exist on certain types of sensory nerves and activation of these receptors promotes and inhibits, respectively, peripheral nerve transmission related to pain and/or inflammation [76,77]. 

Botox is a toxin produced by the bacterium Clostridium botulinum.When Botox is injected into facial tissues, it is absorbed by the nerve endings of muscle fibers. Nerve transmissions are interrupted and consequently the muscle relaxes. The relaxed muscle is then no longer effective to pull the facial lines to show the wrinkles. 

The key to nerve transmission—like most of the biochemical reactions that occur in living organisms—is the concept of a reeeptor molecule, a molecule to which some other molecule hinds. In the example just described, a receptor molecule is a specihc chemical compound with a distinctive shape into which the neurotransmitter molecule can fit. The diagram on page 12 shows how a specihc neurotransmitter has the correct shape to ht into a receptor molecule. 

Chloroprocaine is used in situations requiring fast-acting pain relief. It is also used in infiltration anesthesia, blocking peripheral nerve transmission, and in spinal and epidural anesthesia. Nesacaine is a synonym for chloroprocaine. 

These drugs will be briefly discussed here, for the sake of completeness, for historical reasons and because they have been very useful as tools for the analysis of sympathetic nerve transmission. 

Local anesthetics, when applied at effective concentrations locally to nerve tissue, reversibly block nerve impulse conduction and block somatic sensory, somatic motor and autonomic nerve transmission. Their mechanism of action is based on both... 

Mechanism of Action An anticonvulsant that increases the seizure threshold and suppresses paroxysmal spike-and-wave pattern in absence seizures depresses nerve transmission in the motor cortex. Therapeutic Effect Produces anticonvulsant activity... 

Neurokinins comprise a group of peptides involved in nerve transmission. Specific members of this class of mediators control such diverse functions as visceral regulation and CNS function. The nonpeptide neurokinin antagonist talnetant (32-6), for example, has been evaluated for its effect on irritable bowel syndrome and urinary incontinence as well as depression and schizophrenia [36]. The quinoline portion of this compound is prepared by base-catalyzed Pfitzinger condensation of isatin (32-1) with the methoxy acetophenone (32-2). The methoxy ether in the product (32-3) is next cleaved by means of hydrogen bromide (32-4). Amide formation with the chiral a-phenylpropylamine (32-5) affords the neurokinin antagonist talnetant (32-6) [37]. 

Much of the rather slow information transfer in biological systems is achieved by the release and subsequent transport of messenger molecules. For a fast information transfer over large distances, however, a combination of electrical and chemical transport processes is involved (in part cited from Ref. 1). Since the body is an aqueous organization, rather hostile to free electrons, it comes as no surprise that the carriers of charge are predominantly ions.1 Among the inorganic ions, Na, K+, Ca2+, and Cl- play an essential role in nerve transmission. 

Sequence Determination of the Brain Peptide Leucine Enkephalin A group of peptides that influence nerve transmission in certain parts of the brain has been isolated from normal brain tissue. These peptides are known as opioids, because they bind to specific receptors that also bind opiate drugs, such as morphine and naloxone. Opioids thus mimic some of the properties of opiates. Some researchers consider these peptides to be the brain s own pain killers. Using the information below, determine the amino acid sequence of the opioid leucine enkephalin. Explain how your structure is consistent with each piece of information. 

Long-term cocaine or amphetamine abuse leads to a deterioration of the nervous system. The body recognizes the excessive stimulatory actions produced by these drugs. To deal with the overstimulation, the body creates more depressant receptor sites for neurotransmitters that inhibit nerve transmission. A tolerance for the drugs therefore develops. Then, to receive the same stimulatory effect, the abuser is forced to increase the dose, which induces the body to create even more depressant receptor sites. The end result over the long term is that the abusers natural levels of dopamine and norepinephrine are insufficient to compensate for the excessive number of depressant sites. Lasting personality changes are thus often observed. 

Many of the simplest chemical reactions involve only an interchange of atoms or ions between reactants, or perhaps only the dissociation of one reactant into two parts. In such reactions, there is no change in the electrical charge of any of the atoms involved. This chapter deals with another type of reaction, in which one or more electrons are transferred between atoms, with the result that some of the atoms involved do have their electrical charges changed. These reactions are known as electron-transfer reactions. You can appreciate their importance when you realize that every battery used in electronic devices and machines, every impulse involved in nerve transmission, every metabolic reaction that produces energy in biological systems, photosynthesis, and combustion processes (to mention but a few examples) requires electron-transfer reactions. 

Both are ionotropic. The AMPA receptor channels allow mainly K+ and Na+ to pass and are responsible for most of the nerve transmission. However, the NMDA receptors have an important controlling influence. 

The testing of aminoalkyl quinuclidinecarboxylates, their quaternary halides, and tertiary amino derivatives of 2-mono-, 3-mono-, and 2,3-disubstituted quinuclidines revealed that several were active in breaking nerve transmissions at ganglions. Thus, ethyl quinuclidine-... 

---