Limits...
Large conductance Ca²⁺-activated K⁺ (BK) channels promote secretagogue-induced transition from spiking to bursting in murine anterior pituitary corticotrophs.

Duncan PJ, Şengül S, Tabak J, Ruth P, Bertram R, Shipston MJ - J. Physiol. (Lond.) (2015)

Bottom Line: Anterior pituitary corticotroph cells are a central component of the hypothalamic-pituitary-adrenal (HPA) axis essential for the neuroendocrine response to stress.We reveal that BK channels do not play a significant role in the generation of spontaneous activity but are critical for the transition to bursting in response to CRH.In contrast, AVP promotes an increase in single spike frequency, a mechanism independent of BK channels but dependent on background non-selective conductances.

View Article: PubMed Central - PubMed

Affiliation: Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, EH8 9XD, UK.

No MeSH data available.


Related in: MedlinePlus

Stimulation of corticotrophs with CRH/AVPA, representative current-clamp recording of a corticotroph cell exposed to 0.2 nm CRH and 2 nm AVP for 3 min. Under basal conditions corticotroph cells display predominantly single-spike action potentials (B) which transition to complex bursting patterns following CRH/AVP exposure (C). Grey shading indicates membrane potential between −50 mV and +10 mV. Summary bar graphs illustrating that stimulation with CRH/AVP results in a membrane depolarisation (D) coupled with an increase in event frequency (E), event duration (F) and burstiness factor (BF; G). Data are means ± SEM, (n = 7 per group). *P < 0.05, **P < 0.01, ***P < 0.001, Student's t test compared to base values.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4358680&req=5

fig02: Stimulation of corticotrophs with CRH/AVPA, representative current-clamp recording of a corticotroph cell exposed to 0.2 nm CRH and 2 nm AVP for 3 min. Under basal conditions corticotroph cells display predominantly single-spike action potentials (B) which transition to complex bursting patterns following CRH/AVP exposure (C). Grey shading indicates membrane potential between −50 mV and +10 mV. Summary bar graphs illustrating that stimulation with CRH/AVP results in a membrane depolarisation (D) coupled with an increase in event frequency (E), event duration (F) and burstiness factor (BF; G). Data are means ± SEM, (n = 7 per group). *P < 0.05, **P < 0.01, ***P < 0.001, Student's t test compared to base values.

Mentions: In corticotrophs isolated from POMC-GFP male mice spontaneous activity was observed in more than 90% of cells recorded under current clamp using the perforated patch-clamp approach, as previously observed in female corticotrophs (Liang et al. 2011) with predominantly large amplitude single-spike action potentials (Fig.2A and B). Very occasional longer duration bursts of activity were observed, together with single spike action potentials, in less than 6% of all corticotrophs analysed under basal conditions. Corticotrophs had a resting membrane potential of −53.7 ± 1.5 mV, displayed spontaneous action potentials at a frequency of 0.34 ± 0.14 Hz and had a mean cell capacitance of 4.43 ± 0.94 pF (Fig.2D and E). The mean event duration of 69 ± 26 ms and a burstiness factor (BF) of 0.18 ± 0.10 are both consistent with predominantly single-spike action potential behaviour (Fig.2F and G) in the unstimulated state. Replacement of external sodium ions with the large organic cation N-methyl-d-glucamine (NMDG+) resulted in a significant (P = 0.00059) hyperpolarisation of 22.7 ± 2.8 mV (n = 5) within 1 min, accompanied by a cessation of spontaneous activity which was fully reversible following washout. These data are consistent with those previously observed in female mouse corticotrophs and that a background sodium conductance is important for setting the resting membrane potential of corticotrophs, as in other pituitary cells (Liang et al. 2011; Tomic et al. 2011).


Large conductance Ca²⁺-activated K⁺ (BK) channels promote secretagogue-induced transition from spiking to bursting in murine anterior pituitary corticotrophs.

Duncan PJ, Şengül S, Tabak J, Ruth P, Bertram R, Shipston MJ - J. Physiol. (Lond.) (2015)

Stimulation of corticotrophs with CRH/AVPA, representative current-clamp recording of a corticotroph cell exposed to 0.2 nm CRH and 2 nm AVP for 3 min. Under basal conditions corticotroph cells display predominantly single-spike action potentials (B) which transition to complex bursting patterns following CRH/AVP exposure (C). Grey shading indicates membrane potential between −50 mV and +10 mV. Summary bar graphs illustrating that stimulation with CRH/AVP results in a membrane depolarisation (D) coupled with an increase in event frequency (E), event duration (F) and burstiness factor (BF; G). Data are means ± SEM, (n = 7 per group). *P < 0.05, **P < 0.01, ***P < 0.001, Student's t test compared to base values.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4358680&req=5

fig02: Stimulation of corticotrophs with CRH/AVPA, representative current-clamp recording of a corticotroph cell exposed to 0.2 nm CRH and 2 nm AVP for 3 min. Under basal conditions corticotroph cells display predominantly single-spike action potentials (B) which transition to complex bursting patterns following CRH/AVP exposure (C). Grey shading indicates membrane potential between −50 mV and +10 mV. Summary bar graphs illustrating that stimulation with CRH/AVP results in a membrane depolarisation (D) coupled with an increase in event frequency (E), event duration (F) and burstiness factor (BF; G). Data are means ± SEM, (n = 7 per group). *P < 0.05, **P < 0.01, ***P < 0.001, Student's t test compared to base values.
Mentions: In corticotrophs isolated from POMC-GFP male mice spontaneous activity was observed in more than 90% of cells recorded under current clamp using the perforated patch-clamp approach, as previously observed in female corticotrophs (Liang et al. 2011) with predominantly large amplitude single-spike action potentials (Fig.2A and B). Very occasional longer duration bursts of activity were observed, together with single spike action potentials, in less than 6% of all corticotrophs analysed under basal conditions. Corticotrophs had a resting membrane potential of −53.7 ± 1.5 mV, displayed spontaneous action potentials at a frequency of 0.34 ± 0.14 Hz and had a mean cell capacitance of 4.43 ± 0.94 pF (Fig.2D and E). The mean event duration of 69 ± 26 ms and a burstiness factor (BF) of 0.18 ± 0.10 are both consistent with predominantly single-spike action potential behaviour (Fig.2F and G) in the unstimulated state. Replacement of external sodium ions with the large organic cation N-methyl-d-glucamine (NMDG+) resulted in a significant (P = 0.00059) hyperpolarisation of 22.7 ± 2.8 mV (n = 5) within 1 min, accompanied by a cessation of spontaneous activity which was fully reversible following washout. These data are consistent with those previously observed in female mouse corticotrophs and that a background sodium conductance is important for setting the resting membrane potential of corticotrophs, as in other pituitary cells (Liang et al. 2011; Tomic et al. 2011).

Bottom Line: Anterior pituitary corticotroph cells are a central component of the hypothalamic-pituitary-adrenal (HPA) axis essential for the neuroendocrine response to stress.We reveal that BK channels do not play a significant role in the generation of spontaneous activity but are critical for the transition to bursting in response to CRH.In contrast, AVP promotes an increase in single spike frequency, a mechanism independent of BK channels but dependent on background non-selective conductances.

View Article: PubMed Central - PubMed

Affiliation: Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, EH8 9XD, UK.

No MeSH data available.


Related in: MedlinePlus