A 3-synapse positive feedback loop regulates the excitability of an interneuron critical for sensitization in the leech.
J Neurosci
; 26(13): 3524-31, 2006 Mar 29.
Article
en En
| MEDLINE
| ID: mdl-16571760
ABSTRACT
Sensitization of reflexive shortening in the leech has been linked to serotonin (5-HT)-induced changes in the excitability of a single interneuron, the S cell. This neuron is necessary for sensitization and complete dishabituation of reflexive shortening, during which it contributes to the sensory-motor reflex. The S cell does not contain 5-HT, which is released primarily from the Retzius (R) cells, whose firing enhances S-cell excitability. Here, we show that the S cell excites the R cells, mainly via a fast disynaptic pathway in which the first synapse is the electrical junction between the S cell and the coupling interneurons, and the second synapse is a glutamatergic synapse of the coupling interneurons onto the R cells. The S cell-triggered excitatory postsynaptic potential in the R cell diminishes and nearly disappears in elevated concentrations of divalent cations because the coupling interneurons become inexcitable under these conditions. Serotonin released from the R cells feeds back on the S cell and increases its excitability by activating a 5-HT7-like receptor; 5-methoxytryptamine (5-MeOT; 10 microM) mimics the effects of 5-HT on S cell excitability, and effects of both 5-HT and 5-MeOT are blocked by pimozide (10 microM) and SB-269970 [(R)-3-(2-(2-(4-methylpiperidin-1-yl)-ethyl)pyrrolidine-1-sulfonyl)phenol] (5 microM). This feedback loop may be critical for the full expression of sensitization of reflexive shortening.
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Reflejo
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Transmisión Sináptica
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Potenciales Postsinápticos Excitadores
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Umbral Diferencial
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Interneuronas
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Sanguijuelas
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Red Nerviosa
Límite:
Animals
Idioma:
En
Revista:
J Neurosci
Año:
2006
Tipo del documento:
Article
País de afiliación:
Estados Unidos