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Modulation of Electrical Transmission in Aplysia Bag Cell Neurons by cAMP Through a Postsynaptic Mechanism.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Modulation of Electrical Transmission in Aplysia Bag Cell Neurons by cAMP Through a Postsynaptic Mechanism./
Author:	Prosserman, Alex B.
Description:	1 online resource (104 pages)
Notes:	Source: Masters Abstracts International, Volume: 84-10.
Contained By:	Masters Abstracts International84-10.
Subject:	Physiology. -
Online resource:	click for full text (PQDT)
ISBN:	9798377690429

Modulation of Electrical Transmission in Aplysia Bag Cell Neurons by cAMP Through a Postsynaptic Mechanism.
Prosserman, Alex B.

Modulation of Electrical Transmission in Aplysia Bag Cell Neurons by cAMP Through a Postsynaptic Mechanism. - 1 online resource (104 pages)

Source: Masters Abstracts International, Volume: 84-10.

Thesis (M.Sc.)--Queen's University (Canada), 2023.

Includes bibliographical references

Direct electrical communication between neurons occurs via electrical coupling, which is achieved through paired hemi-channels known as gap junctions. These inter-cellular channels promote synchronized, rapid, and reliable information transfer, thereby affecting the frequency, coordination, and pattern of firing. The present study concerns the electrically coupled bag cell neurons from the sea snail, Aplysia californica. These neuroendocrine cells undergo an ~30-min afterdischarge of continuous firing, culminating with the secretion of egg-laying hormone into the bloodstream. During the afterdischarge, cyclic adenosine monophosphate (cAMP) is quickly increased, and its effector, protein kinase A (PKA), is subsequently upregulated. Yet, it is unknown if cAMP/PKA impact bag cell neurons gap junctions. In culture, paired electrically coupled bag cell neurons present a non-rectifying and voltage-independent junctional conductance. Compared to control, PKA activation with IBMX, a membrane-permeable phosphodiesterase inhibitor, or 8-CPT-cAMP, a cAMP analogue, significantly augmented (~40%) coupling coefficient, a gauge of how well the inter-cellular signal spreads. The height of the electrotonic potential (ETP) evoked by a presynaptic action potential-like waveform was also significantly increased (~30 and ~40%, respectively) by these two reagents, indicative of enhanced electrotonic transmission. However, neither compound altered junctional conductance, suggesting a postsynaptic mechanism. When a junctional-like current was applied to single cells, the resulting ETP-like response was significantly elevated (20-40%) by cAMP, and this was prevented by pretreatment with the PKA inhibitor, KT5720. Next, recordings of either delayed rectifier K+ current, evoked by voltage steps, or more modest K+ current, evoked by an ETP-like voltage change, showed a significant reduction (~25%) after cAMP. Again, these outcomes were eliminated by KT5720, confirming that the effect was PKA-dependent. Moreover, cAMP significantly boosted synchrony and feed-forward excitation, ie, the ability of the presynaptic neuron to evoke postsynaptic action potentials. Overall, these results suggest that PKA enhances electrical transmission by reducing postsynaptic K+ current, making bag cell neurons more responsive to junctional current. Given the critical physiological role of electrically coupled neuroendocrine cells, including those in the vertebrate hypothalamus or adrenal medulla, the insect corpus cardiacum, and the crustacean X-organ, this has implications for the hormonal control of fundamental behaviour.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9798377690429Subjects--Topical Terms:

673386
Physiology.
Index Terms--Genre/Form:

554714
Electronic books.

Modulation of Electrical Transmission in Aplysia Bag Cell Neurons by cAMP Through a Postsynaptic Mechanism.
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245 1 0 $a Modulation of Electrical Transmission in Aplysia Bag Cell Neurons by cAMP Through a Postsynaptic Mechanism.
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500 $a Source: Masters Abstracts International, Volume: 84-10.
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502 $a Thesis (M.Sc.)--Queen's University (Canada), 2023.
504 $a Includes bibliographical references
520 $a Direct electrical communication between neurons occurs via electrical coupling, which is achieved through paired hemi-channels known as gap junctions. These inter-cellular channels promote synchronized, rapid, and reliable information transfer, thereby affecting the frequency, coordination, and pattern of firing. The present study concerns the electrically coupled bag cell neurons from the sea snail, Aplysia californica. These neuroendocrine cells undergo an ~30-min afterdischarge of continuous firing, culminating with the secretion of egg-laying hormone into the bloodstream. During the afterdischarge, cyclic adenosine monophosphate (cAMP) is quickly increased, and its effector, protein kinase A (PKA), is subsequently upregulated. Yet, it is unknown if cAMP/PKA impact bag cell neurons gap junctions. In culture, paired electrically coupled bag cell neurons present a non-rectifying and voltage-independent junctional conductance. Compared to control, PKA activation with IBMX, a membrane-permeable phosphodiesterase inhibitor, or 8-CPT-cAMP, a cAMP analogue, significantly augmented (~40%) coupling coefficient, a gauge of how well the inter-cellular signal spreads. The height of the electrotonic potential (ETP) evoked by a presynaptic action potential-like waveform was also significantly increased (~30 and ~40%, respectively) by these two reagents, indicative of enhanced electrotonic transmission. However, neither compound altered junctional conductance, suggesting a postsynaptic mechanism. When a junctional-like current was applied to single cells, the resulting ETP-like response was significantly elevated (20-40%) by cAMP, and this was prevented by pretreatment with the PKA inhibitor, KT5720. Next, recordings of either delayed rectifier K+ current, evoked by voltage steps, or more modest K+ current, evoked by an ETP-like voltage change, showed a significant reduction (~25%) after cAMP. Again, these outcomes were eliminated by KT5720, confirming that the effect was PKA-dependent. Moreover, cAMP significantly boosted synchrony and feed-forward excitation, ie, the ability of the presynaptic neuron to evoke postsynaptic action potentials. Overall, these results suggest that PKA enhances electrical transmission by reducing postsynaptic K+ current, making bag cell neurons more responsive to junctional current. Given the critical physiological role of electrically coupled neuroendocrine cells, including those in the vertebrate hypothalamus or adrenal medulla, the insect corpus cardiacum, and the crustacean X-organ, this has implications for the hormonal control of fundamental behaviour.
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