Role of a T-type calcium current in supporting a depolarizing potential, damped oscillations, and phasic firing in vasopressinergic guinea pig supraoptic neurons

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Abstract

Guinea pig magnocellular neurosecretory cells (MNCs) of the supraoptic nucleus (SON) were studied using the in vitro slice preparation. Intracellular recordings were made with biocytin-filled electrodes, permitting immunocytochemical identification of the recorded cells as arginine vasopressin- (AVP) versus oxytocin- (OT) containing. Only AVP cells displaying a depolarizing potential (DP) fired phasically. The DP was associated with a transient inward current measured in voltage clamp, which exhibited a number of properties of the T-type calcium current: activation threshold of -64 mV, time course of up to 250 ms, blockade by nickel and augmentation by barium chloride. this current has not been reported previously in SON neurons. The T-type current (I(T)) was always associated with a damped oscillation of the membrane following the offset from hyperpolarizing steps. In all cells tested, an apamin-sensitive afterhyperpolarization (AHP) was observed, similar to the calcium-dependent potassium current (I(K, Ca)) described in rat SON and other CNS regions. Therefore, as with other CNS regions displaying damped oscillations, guinea pig SON cells possess both an I(T) and an I(K, Ca). We have previously described an I(h) activating at hyperpolarized potentials in these cells, which depolarizes the membrane to a range in which the IT and I(K, Ca) can interactively support oscillations. In summary, the I(T) and associated depolarizing potential appears to be a requisite feature for phasic firing in AVP cells of guinea pig SON.

Original languageEnglish (US)
Pages (from-to)789-800
Number of pages12
JournalNeuroendocrinology
Volume57
Issue number5
StatePublished - 1993

Fingerprint

Supraoptic Nucleus
Guinea Pigs
Calcium
Neurons
Arginine Vasopressin
Apamin
Membranes
Oxytocin
Nickel
Cell Nucleus
Potassium
Electrodes

Keywords

  • Calcium current
  • guinea pig
  • immunocytochemistry
  • supraoptic nucleus
  • vasopressin

ASJC Scopus subject areas

  • Endocrinology
  • Neuroscience(all)

Cite this

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title = "Role of a T-type calcium current in supporting a depolarizing potential, damped oscillations, and phasic firing in vasopressinergic guinea pig supraoptic neurons",
abstract = "Guinea pig magnocellular neurosecretory cells (MNCs) of the supraoptic nucleus (SON) were studied using the in vitro slice preparation. Intracellular recordings were made with biocytin-filled electrodes, permitting immunocytochemical identification of the recorded cells as arginine vasopressin- (AVP) versus oxytocin- (OT) containing. Only AVP cells displaying a depolarizing potential (DP) fired phasically. The DP was associated with a transient inward current measured in voltage clamp, which exhibited a number of properties of the T-type calcium current: activation threshold of -64 mV, time course of up to 250 ms, blockade by nickel and augmentation by barium chloride. this current has not been reported previously in SON neurons. The T-type current (I(T)) was always associated with a damped oscillation of the membrane following the offset from hyperpolarizing steps. In all cells tested, an apamin-sensitive afterhyperpolarization (AHP) was observed, similar to the calcium-dependent potassium current (I(K, Ca)) described in rat SON and other CNS regions. Therefore, as with other CNS regions displaying damped oscillations, guinea pig SON cells possess both an I(T) and an I(K, Ca). We have previously described an I(h) activating at hyperpolarized potentials in these cells, which depolarizes the membrane to a range in which the IT and I(K, Ca) can interactively support oscillations. In summary, the I(T) and associated depolarizing potential appears to be a requisite feature for phasic firing in AVP cells of guinea pig SON.",
keywords = "Calcium current, guinea pig, immunocytochemistry, supraoptic nucleus, vasopressin",
author = "Erickson, {K. R.} and Oline Ronnekleiv and Martin Kelly",
year = "1993",
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volume = "57",
pages = "789--800",
journal = "Neuroendocrinology",
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TY - JOUR

T1 - Role of a T-type calcium current in supporting a depolarizing potential, damped oscillations, and phasic firing in vasopressinergic guinea pig supraoptic neurons

AU - Erickson, K. R.

AU - Ronnekleiv, Oline

AU - Kelly, Martin

PY - 1993

Y1 - 1993

N2 - Guinea pig magnocellular neurosecretory cells (MNCs) of the supraoptic nucleus (SON) were studied using the in vitro slice preparation. Intracellular recordings were made with biocytin-filled electrodes, permitting immunocytochemical identification of the recorded cells as arginine vasopressin- (AVP) versus oxytocin- (OT) containing. Only AVP cells displaying a depolarizing potential (DP) fired phasically. The DP was associated with a transient inward current measured in voltage clamp, which exhibited a number of properties of the T-type calcium current: activation threshold of -64 mV, time course of up to 250 ms, blockade by nickel and augmentation by barium chloride. this current has not been reported previously in SON neurons. The T-type current (I(T)) was always associated with a damped oscillation of the membrane following the offset from hyperpolarizing steps. In all cells tested, an apamin-sensitive afterhyperpolarization (AHP) was observed, similar to the calcium-dependent potassium current (I(K, Ca)) described in rat SON and other CNS regions. Therefore, as with other CNS regions displaying damped oscillations, guinea pig SON cells possess both an I(T) and an I(K, Ca). We have previously described an I(h) activating at hyperpolarized potentials in these cells, which depolarizes the membrane to a range in which the IT and I(K, Ca) can interactively support oscillations. In summary, the I(T) and associated depolarizing potential appears to be a requisite feature for phasic firing in AVP cells of guinea pig SON.

AB - Guinea pig magnocellular neurosecretory cells (MNCs) of the supraoptic nucleus (SON) were studied using the in vitro slice preparation. Intracellular recordings were made with biocytin-filled electrodes, permitting immunocytochemical identification of the recorded cells as arginine vasopressin- (AVP) versus oxytocin- (OT) containing. Only AVP cells displaying a depolarizing potential (DP) fired phasically. The DP was associated with a transient inward current measured in voltage clamp, which exhibited a number of properties of the T-type calcium current: activation threshold of -64 mV, time course of up to 250 ms, blockade by nickel and augmentation by barium chloride. this current has not been reported previously in SON neurons. The T-type current (I(T)) was always associated with a damped oscillation of the membrane following the offset from hyperpolarizing steps. In all cells tested, an apamin-sensitive afterhyperpolarization (AHP) was observed, similar to the calcium-dependent potassium current (I(K, Ca)) described in rat SON and other CNS regions. Therefore, as with other CNS regions displaying damped oscillations, guinea pig SON cells possess both an I(T) and an I(K, Ca). We have previously described an I(h) activating at hyperpolarized potentials in these cells, which depolarizes the membrane to a range in which the IT and I(K, Ca) can interactively support oscillations. In summary, the I(T) and associated depolarizing potential appears to be a requisite feature for phasic firing in AVP cells of guinea pig SON.

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