scholarly journals Augmentation of calcium channel currents in response to G protein activation by GTP gamma S in chick sensory neurons

1994 ◽  
Vol 14 (8) ◽  
pp. 4847-4853 ◽  
Author(s):  
X Zong ◽  
HD Lux
Keyword(s):  
Calcium Channel ◽  
G Protein ◽  
Sensory Neurons ◽  
Protein Activation ◽  
G Protein Activation ◽  
Gamma S ◽  
Channel Currents

scholarly journals The detergent Solulan C-24 reveals properties of the olfactory adenylate cyclase system

1989 ◽  
Vol 260 (3) ◽  
pp. 683-687 ◽  
Author(s):  
C J Robinson ◽  
S G Shirley ◽  
G H Dodd
Keyword(s):  
Adenylate Cyclase ◽  
G Protein ◽  
Cyclase Activity ◽  
Adenylate Cyclase System ◽  
Protein Activation ◽  
Maximal Stimulation ◽  
G Protein Activation ◽  
Stimulatory G Protein ◽  
Atp Inhibition ◽  
Gamma S

The detergent Solulan C-24 has been shown to activate the olfactory adenylate cyclase, with loss of the odorant modulation, at concentrations too low to cause significant solubilization. The activation is synergistic with that of nonhydrolysable GTP analogues, forskolin and AlF4-. These effects are not reversible. Solulan causes the cyclase activity to become subject to ATP inhibition, which is competitively relieved by GTP gamma S, and increases the GTP gamma S concentration required for half-maximal stimulation of the system. This suggests a change in the GTP-binding site of the stimulatory G-protein. Activation by GTP gamma S, without Solulan, indicates that the cyclase catalytic unit, rather than the available G-protein, may be limiting in the system. We suggest that Solulan may remove an inhibitory control on the cyclase activity.

Opioid-Activated Postsynaptic, Inward Rectifying Potassium Currents in Whole Cell Recordings in Substantia Gelatinosa Neurons

1998 ◽  
Vol 80 (6) ◽  
pp. 2954-2962 ◽  
Author(s):  
S. P. Schneider ◽  
W. A. Eckert ◽  
A. R. Light
Keyword(s):  
Membrane Potential ◽  
G Protein ◽  
Potassium Currents ◽  
Substantia Gelatinosa ◽  
Opioid Agonist ◽  
Membrane Hyperpolarization ◽  
Whole Cell ◽  
Protein Activation ◽  
G Protein Activation ◽  
Whole Cell Recordings

Schneider, S. P., W. A. Eckert III, and A. R. Light. Opioid-activated postsynaptic, inward rectifying potassium currents in whole cell recordings in substantia gelatinosa neurons. J. Neurophysiol. 80: 2954–2962, 1998. Using tight-seal, whole cell recordings from isolated transverse slices of hamster and rat spinal cord, we investigated the effects of the μ-opioid agonist (d-Ala2, N-Me-Phe4,Gly5-ol)-enkephalin (DAMGO) on the membrane potential and conductance of substantia gelatinosa (SG) neurons. We observed that bath application of 1–5 μM DAMGO caused a robust and repeatable hyperpolarization in membrane potential ( V m) and decrease in neuronal input resistance ( R N) in 60% (27/45) of hamster neurons and 39% (9/23) of rat neurons, but significantly only when ATP (2 mM) and guanosine 5′-triphosphate (GTP; 100 μM) were included in the patch pipette internal solution. An ED50 of 50 nM was observed for the hyperpolarization in rat SG neurons. Because G-protein mediation of opioid effects has been shown in other systems, we tested if the nucleotide requirement for opioid hyperpolarization in SG neurons was due to G-protein activation. GTP was replaced with the nonhydrolyzable GTP analogue guanosine-5′- O-(3-thiotriphosphate) (GTP-γ-S; 100 μM), which enabled DAMGO to activate a nonreversible membrane hyperpolarization. Further, intracellular application of guanosine-5′- O-(2-thiodiphosphate) (GDP-β-S; 500 μM), which blocks G-protein activation, abolished the effects of DAMGO. We conclude that spinal SG neurons are particularly susceptible to dialysis of GTP by whole cell recording techniques. Moreover, the depletion of GTP leads to the inactivation of G-proteins that mediate μ-opioid activation of an inward-rectifying, potassium conductance in these neurons. These results explain the discrepancy between the opioid-activated hyperpolarization in SG neurons observed in previous sharp electrode experiments and the more recent failures to observe these effects with whole cell patch techniques.

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