Limits...
Modulation of voltage-gated Ca2+ channels by G protein-coupled receptors in celiac-mesenteric ganglion neurons of septic rats.

Farrag M, Laufenberg LJ, Steiner JL, Weller GE, Lang CH, Ruiz-Velasco V - PLoS ONE (2015)

Bottom Line: We used the cecal ligation puncture (CLP) model, which closely mimics the hemodynamic and metabolic disturbances observed in septic patients, to examine the properties and modulation of Ca2+ channels by G protein-coupled receptors in acutely dissociated rat CSMG neurons.This reduction coincided with a significant increase in membrane surface area and a negligible increase in Ca2+ current amplitude.Testing for the presence of opioid receptor subtypes in CSMG neurons, showed that mu opioid receptors were present in ~70% of CSMG, while NOP opioid receptors were found in all CSMG neurons tested.

View Article: PubMed Central - PubMed

Affiliation: Department of Anesthesiology, Penn State College of Medicine, Hershey, PA, United States of America.

ABSTRACT
Septic shock, the most severe complication associated with sepsis, is manifested by tissue hypoperfusion due, in part, to cardiovascular and autonomic dysfunction. In many cases, the splanchnic circulation becomes vasoplegic. The celiac-superior mesenteric ganglion (CSMG) sympathetic neurons provide the main autonomic input to these vessels. We used the cecal ligation puncture (CLP) model, which closely mimics the hemodynamic and metabolic disturbances observed in septic patients, to examine the properties and modulation of Ca2+ channels by G protein-coupled receptors in acutely dissociated rat CSMG neurons. Voltage-clamp studies 48 hr post-sepsis revealed that the Ca2+ current density in CMSG neurons from septic rats was significantly lower than those isolated from sham control rats. This reduction coincided with a significant increase in membrane surface area and a negligible increase in Ca2+ current amplitude. Possible explanations for these findings include either cell swelling or neurite outgrowth enhancement of CSMG neurons from septic rats. Additionally, a significant rightward shift of the concentration-response relationship for the norepinephrine (NE)-mediated Ca2+ current inhibition was observed in CSMG neurons from septic rats. Testing for the presence of opioid receptor subtypes in CSMG neurons, showed that mu opioid receptors were present in ~70% of CSMG, while NOP opioid receptors were found in all CSMG neurons tested. The pharmacological profile for both opioid receptor subtypes was not significantly affected by sepsis. Further, the Ca2+ current modulation by propionate, an agonist for the free fatty acid receptors GPR41 and GPR43, was not altered by sepsis. Overall, our findings suggest that CSMG function is affected by sepsis via changes in cell size and α2-adrenergic receptor-mediated Ca2+ channel modulation.

No MeSH data available.


Related in: MedlinePlus

Biophysical properties of CSMG neurons from sham control and septic rats.Measurement of the mean absolute Ca2+ current amplitude (A) at the depolarizing potential to +10 mV. Ca2+ current density (B) was calculated from the peak Ca2+ current amplitude at the test pulse of +10 mV and normalized to membrane capacitance. The cell membrane capacitance (C) was determined from the numerical integration of a transient elicited with a depolarizing pulse from -80 mV to -70 mV prior to electronic compensation. Summary graph of the basal facilitation ratio (D), calculated as the ratio of Ca2+ current amplitude determined from the test pulse (+10 mV) occurring after (postpulse) and before (prepulse) the +80 mV conditioning pulse (see Fig 3A, top right). The current amplitude was measured isochronally 10 ms after initiation of the test pulse. The numbers in parenthesis indicate the number of neurons tested; * indicates P < 0.05, unpaired t-test, NS indicates not significantly different, P > 0.05.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4446366&req=5

pone.0125566.g002: Biophysical properties of CSMG neurons from sham control and septic rats.Measurement of the mean absolute Ca2+ current amplitude (A) at the depolarizing potential to +10 mV. Ca2+ current density (B) was calculated from the peak Ca2+ current amplitude at the test pulse of +10 mV and normalized to membrane capacitance. The cell membrane capacitance (C) was determined from the numerical integration of a transient elicited with a depolarizing pulse from -80 mV to -70 mV prior to electronic compensation. Summary graph of the basal facilitation ratio (D), calculated as the ratio of Ca2+ current amplitude determined from the test pulse (+10 mV) occurring after (postpulse) and before (prepulse) the +80 mV conditioning pulse (see Fig 3A, top right). The current amplitude was measured isochronally 10 ms after initiation of the test pulse. The numbers in parenthesis indicate the number of neurons tested; * indicates P < 0.05, unpaired t-test, NS indicates not significantly different, P > 0.05.

Mentions: Fig 2A is a summary plot of the absolute Ca2+ current amplitude obtained from both groups of neurons. The results show that the current amplitude was slightly greater (P = 0.70) in CSMG neurons isolated from septic rats compared to neurons from sham control rats. On the other hand, the plot in Fig 2B indicates that the neuron capacitance, a measure of surface area, was significantly (P < 0.05) higher in neurons from septic rats. As a result, the Ca2+ current density was significantly (P < 0.05) reduced compared to neurons from sham control rats (Fig 2C).


Modulation of voltage-gated Ca2+ channels by G protein-coupled receptors in celiac-mesenteric ganglion neurons of septic rats.

Farrag M, Laufenberg LJ, Steiner JL, Weller GE, Lang CH, Ruiz-Velasco V - PLoS ONE (2015)

Biophysical properties of CSMG neurons from sham control and septic rats.Measurement of the mean absolute Ca2+ current amplitude (A) at the depolarizing potential to +10 mV. Ca2+ current density (B) was calculated from the peak Ca2+ current amplitude at the test pulse of +10 mV and normalized to membrane capacitance. The cell membrane capacitance (C) was determined from the numerical integration of a transient elicited with a depolarizing pulse from -80 mV to -70 mV prior to electronic compensation. Summary graph of the basal facilitation ratio (D), calculated as the ratio of Ca2+ current amplitude determined from the test pulse (+10 mV) occurring after (postpulse) and before (prepulse) the +80 mV conditioning pulse (see Fig 3A, top right). The current amplitude was measured isochronally 10 ms after initiation of the test pulse. The numbers in parenthesis indicate the number of neurons tested; * indicates P < 0.05, unpaired t-test, NS indicates not significantly different, P > 0.05.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4446366&req=5

pone.0125566.g002: Biophysical properties of CSMG neurons from sham control and septic rats.Measurement of the mean absolute Ca2+ current amplitude (A) at the depolarizing potential to +10 mV. Ca2+ current density (B) was calculated from the peak Ca2+ current amplitude at the test pulse of +10 mV and normalized to membrane capacitance. The cell membrane capacitance (C) was determined from the numerical integration of a transient elicited with a depolarizing pulse from -80 mV to -70 mV prior to electronic compensation. Summary graph of the basal facilitation ratio (D), calculated as the ratio of Ca2+ current amplitude determined from the test pulse (+10 mV) occurring after (postpulse) and before (prepulse) the +80 mV conditioning pulse (see Fig 3A, top right). The current amplitude was measured isochronally 10 ms after initiation of the test pulse. The numbers in parenthesis indicate the number of neurons tested; * indicates P < 0.05, unpaired t-test, NS indicates not significantly different, P > 0.05.
Mentions: Fig 2A is a summary plot of the absolute Ca2+ current amplitude obtained from both groups of neurons. The results show that the current amplitude was slightly greater (P = 0.70) in CSMG neurons isolated from septic rats compared to neurons from sham control rats. On the other hand, the plot in Fig 2B indicates that the neuron capacitance, a measure of surface area, was significantly (P < 0.05) higher in neurons from septic rats. As a result, the Ca2+ current density was significantly (P < 0.05) reduced compared to neurons from sham control rats (Fig 2C).

Bottom Line: We used the cecal ligation puncture (CLP) model, which closely mimics the hemodynamic and metabolic disturbances observed in septic patients, to examine the properties and modulation of Ca2+ channels by G protein-coupled receptors in acutely dissociated rat CSMG neurons.This reduction coincided with a significant increase in membrane surface area and a negligible increase in Ca2+ current amplitude.Testing for the presence of opioid receptor subtypes in CSMG neurons, showed that mu opioid receptors were present in ~70% of CSMG, while NOP opioid receptors were found in all CSMG neurons tested.

View Article: PubMed Central - PubMed

Affiliation: Department of Anesthesiology, Penn State College of Medicine, Hershey, PA, United States of America.

ABSTRACT
Septic shock, the most severe complication associated with sepsis, is manifested by tissue hypoperfusion due, in part, to cardiovascular and autonomic dysfunction. In many cases, the splanchnic circulation becomes vasoplegic. The celiac-superior mesenteric ganglion (CSMG) sympathetic neurons provide the main autonomic input to these vessels. We used the cecal ligation puncture (CLP) model, which closely mimics the hemodynamic and metabolic disturbances observed in septic patients, to examine the properties and modulation of Ca2+ channels by G protein-coupled receptors in acutely dissociated rat CSMG neurons. Voltage-clamp studies 48 hr post-sepsis revealed that the Ca2+ current density in CMSG neurons from septic rats was significantly lower than those isolated from sham control rats. This reduction coincided with a significant increase in membrane surface area and a negligible increase in Ca2+ current amplitude. Possible explanations for these findings include either cell swelling or neurite outgrowth enhancement of CSMG neurons from septic rats. Additionally, a significant rightward shift of the concentration-response relationship for the norepinephrine (NE)-mediated Ca2+ current inhibition was observed in CSMG neurons from septic rats. Testing for the presence of opioid receptor subtypes in CSMG neurons, showed that mu opioid receptors were present in ~70% of CSMG, while NOP opioid receptors were found in all CSMG neurons tested. The pharmacological profile for both opioid receptor subtypes was not significantly affected by sepsis. Further, the Ca2+ current modulation by propionate, an agonist for the free fatty acid receptors GPR41 and GPR43, was not altered by sepsis. Overall, our findings suggest that CSMG function is affected by sepsis via changes in cell size and α2-adrenergic receptor-mediated Ca2+ channel modulation.

No MeSH data available.


Related in: MedlinePlus