Nicotinic response

Uteshev, V. V., Stevens, D. R. Haas, H. L. (1996). Alpha-bungarotoxin-sensitive nicotinic responses in rat tuberomammillary neurons. Pflugers Arch. Bur. J. 

Both muscarinic and nicotinic responses are elicited in brain and spinal cord 189... 

Acetylcholine (9.12) binds both types of cholinergic receptors muscarinic and nicotinic (Figure 9.9). The names of these receptor types were based on muscarine (9.13) and nicotine (9.14), selective agonists for each receptor. A muscarinic response is characterized by nausea, salivation, and tearing. Nicotinic responses are noted by an acceleration of the heart rate. Acetylcholine s ability to elicit a response from both subtypes of receptors may imply that different conformations of acetylcholine may be responsible for binding to each receptor. 

There is a correlation between the response to supramaximal electrical stimulation and the withdrawal response (contraction) precipitated with 100 nM naloxone as well as a correlation between withdrawal and nicotine response after long-term exposure (12-48 h) with 480 nM morphine. 

First, the hornworm larvae may suppress the plant s nicotine response or they may reduce their food intake and therefore run less risk to alert the plant s nicotine response. 

Third, the plant may suppress the nicotine response until the hornworm larvae reach a size (i.e., fourth or fifth instar) where they impose a serious death risk to the tobacco plant and then switch to produce nicotine to make these large larvae move to their neighboring competitors.210... 

We begin our study by perforaiing mole balances on each chemical species in the system. Here, the tenn chemical species refers to any chemical compound or element with a given identity. The identity of a chemical species is determined by the kind, number, and configuration of that species atoms. For example, the species nicotine (a bad tobacco alkaloid) is made up of a fixed number of specific elements in a definite molecular arrangement or configuration. The structure shown illustrates the kind, number, and configuration of the species nicotine (responsible for nicotine fits ) on a molecular level. 

Langley J. On the contraction of muscle, chiefly in relation to the presence of receptive substances. IV The effect of curari and of some other substances on the nicotine response of the sartorius and gastroenemius muscles of the frog. J Physiol (Lond) 1909 39 235-295. 

Finally, changes in extracellular calcium (in the low millimolar range) can modulate nicotinic responses. Increases in calcium concentration strongly enhance macroscopic responses of either native or recombinant heteromeric nicotinic receptors to low ACh concentrations, decreasing the BC value of ACh and increasing the Hill slope of the curve (133, 140, 160, 161). This effect is not seen with muscle embryonic channels (133). In native a7 receptors the modulation has been reported to be biphasic, with potentiation at submillimolar calcium concentrations and depression at higher concentrations (162). The sequence determinants for this effect have... 

The first descriptions of nicotinic responses in hippocampus refer to agonist responses recorded in long-term primary cultures (213, 214). Three main types of agonist responses were described, broadly corresponding to 7, a4]82, and a3j34-like responses [reviewed in Albuquerque et al. (215)]. 

In hippocampal cultures, other less common types of nicotinic responses were the slower a-bungarotoxin resistant types II and... 

III. C>f these, type II is the most common (10% of neurons in primary culture) and may correspond to a4j32. It is very sensitive to dihydro-jS-erythroidine (10 nM) and is decreased by high concentrations of methyllycaconitine (100 nM). It is also blocked by mecamylamine (I fxM). The most rare and slow responses were termed type III (2%of hippocampal neurons in culture) these may correspond to o 3j34 receptors, are sensitive to I fiM-mecamylamine or 20 ixM tubocurarine, and resistant to 100 nM methyllycaconitine. This classification is likely to hold outside the hippocampus as well, as shown by results in normal and 32-knockout mice [see, for instance, Zoli et al. (212), who distinguish a fourth type of nicotinic response, similar to type III, but with faster desensitization at high nicotine doses and different properties in equilibrium binding assays with agonists]. 

In Nature, no less than two molecules of ACh must combine with the a-protein to evoke a response. One microsecond pulse of ACh produces, in skeletal muscle, an apparently instant response that lasts for 10 fJLS. These figures suggest that the receptor directly controls the micropore, and that no phosphorylation step is required. Thus the nicotinic response is much simpler and more direct than that postulated by Greengard for the muscarinic response (P-522). 

Boska P, Livett B. Substance P protects against densensitization of the nicotinic response in isolated adrenal chromaffin cells. J Neurochem 1984 42 618-627. 

Adrenal medulla Bovine Release of catecholamines inhibition of nicotinic response in presence of tetrodotoxin (164. 165)... 

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