Cholecystokinin and Acetylcholine Activation of Single-Channel Currents via Second Messenger in Pancreatic Acinar Cells

1983 ◽  
pp. 425-435 ◽  
Author(s):  
O. H. Petersen ◽  
Y. Maruyama
Keyword(s):  
Single Channel ◽  
Acinar Cells ◽  
Second Messenger ◽  
Pancreatic Acinar Cells ◽  
Single Channel Currents ◽  
Channel Currents

Potassium Channels and Fluid Secretion

Physiology ◽  
1986 ◽  
Vol 1 (3) ◽  
pp. 92-95
Author(s):  
OH Peterson
Keyword(s):  
Potassium Channels ◽  
Patch Clamp ◽  
Single Channel ◽  
Acinar Cells ◽  
Fluid Secretion ◽  
Exocrine Glands ◽  
Great Precision ◽  
K Channels ◽  
Single Channel Currents ◽  
Channel Currents

Fluid secretion from exocrine glands can be switched on and off with great precision. Recent patch-clamp recordings of single-channel currents in acinar cells reveals that neurotransmitters and hormones control the opening of K+ channels. However, fluid secretion is due to transport of Na+ and Cl-, and movement of these ions occurs only when K+ can be transported simultaneously. Thus, by controlling K+ channels, neurotransmitters or hormones regulate Na+ and Cl-secretion.

Are second messengers crucial for opening the pore associated with P2X7receptor?

2005 ◽  
Vol 288 (2) ◽  
pp. C260-C271 ◽  
Author(s):  
R. X. Faria ◽  
F. P. DeFarias ◽  
Luiz Anastácio Alves
Keyword(s):  
Cell Membrane ◽  
Pore Formation ◽  
Single Channel ◽  
Second Messengers ◽  
Second Messenger ◽  
Fluorescent Imaging ◽  
Cationic Channels ◽  
Intracellular Ca ◽  
Single Channel Currents ◽  
Channel Currents

Stimulation of the P2X7receptor by ATP induces cell membrane depolarization, increase in intracellular Ca2+concentration, and, in most cases, permeabilization of the cell membrane to molecules up to 900 Da. After the activation of P2X7, at least two phenomena occur: the opening of low-conductance (8 pS) cationic channels and pore formation. At least two conflicting hypotheses have been postulated to reconcile these findings: 1) the P2X7pore is formed as a result of gradual permeability increase (dilation) of cationic channels, and 2) the P2X7pore represents a distinct channel, possibly activated by a second messenger and not directly by extracellular nucleotides. In this study, we investigated whether second messengers are necessary to open the pore associated with the P2X7receptor in cells that expressed the pore activity by using the patch-clamp technique in whole cell and cell-attached configurations in conjunction with fluorescent imaging. In peritoneal macrophages and 2BH4 cells, we detected permeabilization and single-channel currents in the cell-attached configuration when ATP was applied outside the membrane patch in a condition in which oxidized ATP and Lucifer yellow were maintained within the pipette. Our data support Ca2+as a second messenger associated with pore formation because the permeabilization depended on the presence of intracellular Ca2+and was blocked by BAPTA-AM. In addition, MAPK inhibitors (SB-203580 and PD-98059) blocked the permeabilization and single-channel currents in these cells. Together our data indicate that the P2X7pore depends on second messengers such as Ca2+and MAP kinases.

A Calcium-Activated Nonspecific Cation Channel from Olfactory Receptor Neurones of the Silkmoth Antheraea Polyphemus

1991 ◽  
Vol 161 (1) ◽  
pp. 455-468
Author(s):  
F. ZUFALL ◽  
H. HATT ◽  
T. A. KEIL
Keyword(s):  
Olfactory Receptor ◽  
Single Channel ◽  
Membrane Vesicles ◽  
Cation Channel ◽  
Voltage Response ◽  
Antheraea Polyphemus ◽  
Cell Excitability ◽  
Olfactory Receptor Neurones ◽  
Single Channel Currents ◽  
Channel Currents

Single-channel patch-clamp techniques were used to identify and characterize a Ca2+-activated nonspecific cation channel (CAN channel) on insect olfactory receptor neurones (ORNs) from antennae of male Antheraea polyphemus. The CAN channel was found both in acutely isolated ORNs from developing pupae and in membrane vesicles from mature ORNs that presumably originated from inner dendritic segments. Amplitude histograms of the CAN single-channel currents presented well-defined peaks corresponding to at least four channel substates each having a conductance of about 16 pS. Simultaneous gating of the substates was achieved by intracellular Ca2+ with an EC50 value of about 80 nmoll−1. Activity of the CAN channel could be blocked by application of amiloride (IC50 <100nmoll−1). Moreover, in the presence of 1μmoll−1 Ca2+, opening of the CAN channel was totally suppressed by 10 μmoll−1 cyclic GMP, whereas ATP (1 mmol l−1) was without effect. We suggest that the CAN channel plays a specific role in modulation of cell excitability and in shaping the voltage response of ORNs.

Sign in / Sign up

Export Citation Format

Share Document