Nicotinic acetylcholine receptors as modulators off sympathetic neurons and sattelit glial cells protein-synthesizing systems in cranial cervical ganglion

1. We have investigated the pharmacological properties of functional nicotinic acetylcholine receptors (nAChRs) on neonatal rat sympathetic neurons from the superior cervical ganglion (SCG) to learn more about the subunit composition of these receptors. These neurons express five nAChR transcripts: alpha 3, alpha 5, alpha 7, beta 2, and beta 4; this finding suggests that SCG neurons may express several different, physiologically distinct, subtypes of nAChRs. 2. To identify potential subtypes, we have characterized currents evoked by different nicotinic agonists and determined their sensitivity to blockade by alpha-bungarotoxin (alpha-BTX) and by neuronal bungarotoxin (n-BTX). From dose-response curves, we find that the ED50 for both cytisine and dimethylphenylpiperazinium (DMPP) is 20 microM and for ACh is 52 microM. n-BTX blocks the ACh-gated currents rapidly, but the kinetics for n-BTX removal is dependent on the duration of the application: brief applications were quickly reversible, whereas prolonged applications took orders of magnitude longer to reverse. 3. Using fast (ms) agonist application, we observed no rapidly desensitizing currents despite the high levels of alpha 7 in these neurons, nor did we observe any currents that could be blocked by alpha-BTX. 4. Using Xenopus oocytes expressing alpha 7 receptors, we show that choline evokes a significant current that is blocked by alpha-BTX. In contrast, choline is much less potent on alpha 3 beta 4 receptors expressed in Xenopus oocytes. Choline can also act as a weak agonist for nAChRs on rat SCG neurons, but its evoked current is not blocked by alpha-BTX. 5. Our results indicate that, when measured at the macroscopic level, most functional nAChRs on SCG neurons behave as a uniform population of receptors, at least with respect to agonist activation and toxin blockade. In comparison with known receptors expressed in heterologous systems, the physiological properties of ACh-evoked currents on SCG neurons are most similar to receptors that have coassembled with both beta 2 and beta 4.

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Genetic dissection of nicotinic acetylcholine receptors in sympathetic neurons

Autonomic Neuroscience ◽

10.1016/j.autneu.2013.05.074 ◽

2013 ◽

Vol 177 (1) ◽

pp. 40

Author(s):

S. Huck ◽

A. Ciuraszkiewicz ◽

W. Schreibmayer ◽

W.D. Platzer ◽

A. Orr-Urtreger ◽

...

Keyword(s):

Nicotinic Acetylcholine Receptors ◽

Acetylcholine Receptors ◽

Sympathetic Neurons ◽

Genetic Dissection ◽

Nicotinic Acetylcholine

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Expression of nicotinic acetylcholine receptors in the rat superior cervical ganglion on mRNA and protein level

Molecular Brain Research ◽

10.1016/0169-328x(94)90199-6 ◽

1994 ◽

Vol 27 (1) ◽

pp. 167-173 ◽

Cited By ~ 15

Author(s):

L. Klimaschewski ◽

S. Reuss ◽

R. Spessert ◽

C. Lobron ◽

A. Wevers ◽

...

Keyword(s):

Nicotinic Acetylcholine Receptors ◽

Superior Cervical Ganglion ◽

Protein Level ◽

Acetylcholine Receptors ◽

Nicotinic Acetylcholine ◽

Cervical Ganglion

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Calcium Flux Through Predominantly Independent Purinergic ATP and Nicotinic Acetylcholine Receptors

Journal of Neurophysiology ◽

10.1152/jn.1997.77.3.1407 ◽

1997 ◽

Vol 77 (3) ◽

pp. 1407-1417 ◽

Cited By ~ 32

Author(s):

Marc Rogers ◽

Lorna M. Colquhoun ◽

James W. Patrick ◽

John A. Dani

Keyword(s):

Nicotinic Acetylcholine Receptors ◽

Acetylcholine Receptors ◽

Open Channel ◽

Sympathetic Neurons ◽

Cross Reactivity ◽

Calcium Flux ◽

Nicotinic Acetylcholine ◽

Atp Receptors ◽

Intracellular Signals ◽

Activity Dependent

Rogers, Marc, Lorna M. Colquhoun, James W. Patrick, and John A. Dani. Calcium flux through predominantly independent purinergic ATP and nicotinic acetylcholine receptors. J. Neurophysiol. 77: 1407–1417, 1997. Ligand-gated nicotinic acetylcholine receptors (nAChRs) and purinergic ATP receptors are often expressed in the same peripheral and central neurons, and ATP and acetylcholine (ACh) are stored together in some synaptic vesicles. Evidence has suggested that nAChRs and ATP receptors are not independent and that some agonists strongly cross-activate and desensitize both receptor types. Rat sympathetic neurons and nAChRs expressed in Xenopus oocytes were studied to determine the significance of the interactions caused by the two agonist types. Current amplitudes induced with separate or combined applications of ATP and nicotine are >90% additive and independent. Half of all neurons tested responded to either ATP or nicotine but not to both, indicating differences in the expression of the two receptors. In neurons that expressed both receptor types, the nAChRs were inhibited by the activity-dependent open-channel blocker chlorisondamine. If the purinergic and nicotinic receptors were significantly dependent and coactivated, then blocking the ion channels opened by a nicotinic agonist should diminish the current activated by a purinergic agonist. That result was not seen; rather, complete open-channel block of nAChRs with chlorisondamine did not significantly alter the amplitude or kinetics of ATP-induced currents in the same neurons. Finally, when cloned nAChR subunits were expressed in oocytes, ATP activated only very small currents compared with the current activated by ACh. For the 13 different nAChR subunit combinations that were studied, ATP (50–500 μM) activated a current that ranged from 0 to 4% of the size of the current activated by 100 μM ACh. In summary, we find that there is little cross reactivity, and nAChRs and purinergic ATP receptors are predominately independent, acting with separable physiological characteristics. Therefore the quantitative Ca2+ flux could be separately determined for nAChRs and ATP receptors. The fraction of total current that is carried by Ca2+ was quantitatively determined by simultaneously measuring the whole cell current and the associated change in intracellular Ca2+ with fura-2. For sympathetic neurons bathed in 2.5 mM Ca2+ at a holding potential of −50 mV, Ca2+ carries 4.8 ± 0.3% (mean ± SE) of the inward current through neuronal nAChRs and 6.5 ± 0.1% of the current through purinergic ATP receptors. In conclusion, activity-dependent Ca2+ influx through predominately independent populations of nAChRs and ATP receptors can produce different intracellular signals at purinergic and cholinergic synapses.

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