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Gonadotropin-releasing hormone-1 neuronal activity is independent of cyclic nucleotide-gated channels.

ABSTRACT: Pulsatile release of GnRH-1 is essential for secretion of gonadotropin hormones. The frequency of GnRH-1 pulses is regulated during the reproductive cycle by numerous neurotransmitters. Cyclic nucleotide-gated (CNG) channels have been proposed as a mechanism to integrate the cAMP signal evoked by many neurotransmitters. This study reports the expression of the CNGA2 subunit in GnRH-1 neurons obtained from mouse nasal explants and shows the ability of GnRH-1 neurons to increase their activity in response to forskolin (activator of adenylyl cyclases), or 3-isobutyl-1-methylxanthine (inhibitor of phosphodiesterases) even after removal of gamma-aminobutyric acid (A)-ergic input. Next, the endogenous activity of adenylyl cyclases was evaluated as a component of the oscillatory mechanism of GnRH-1 neurons. Inhibition of endogenous activity of adenylyl cyclases did not alter GnRH-1 activity. The potential involvement of CNGA2 subunit in basal or induced activity was tested on GnRH-1 neurons obtained from CNGA2-deficient mice. Without up-regulation of CNGA1 or CNGA3, the absence of functional CNGA2 did not alter either the endogenous GnRH-1 neuronal activity or the response to forskolin, negating CNG channels from cAMP-sensitive mechanisms leading to changes in GnRH-1 neuronal activity. In addition, the potential role of CNGA2 subunit in the synchronization of calcium oscillations previously described was evaluated in GnRH-1 neurons from CNGA2-deficient explants. Synchronized calcium oscillations persisted in CNGA2-deficient GnRH-1 neurons. Taken together, these results indicate that CNGA2 channels are not necessary for either the response of GnRH-1 neurons to cAMP increases or the basal rhythmic activity of GnRH-1 neurons.

SUBMITTER: Constantin S

PROVIDER: S-EPMC2194613 | biostudies-literature | 2008 Jan

REPOSITORIES: biostudies-literature

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Gonadotropin-releasing hormone-1 neuronal activity is independent of cyclic nucleotide-gated channels.

Constantin Stéphanie S Wray Susan S

Endocrinology 20071004 1

Pulsatile release of GnRH-1 is essential for secretion of gonadotropin hormones. The frequency of GnRH-1 pulses is regulated during the reproductive cycle by numerous neurotransmitters. Cyclic nucleotide-gated (CNG) channels have been proposed as a mechanism to integrate the cAMP signal evoked by many neurotransmitters. This study reports the expression of the CNGA2 subunit in GnRH-1 neurons obtained from mouse nasal explants and shows the ability of GnRH-1 neurons to increase their activity in ...[more]

PMID: 17916627

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Project description:Analysis of transcriptome in moss Physcomitrella patens CNGCb null mutant at 25 and 34 degrees C for 30 minutes. Results provide insight into role of CNGCb in acquired thermotolerance induced by non-lethal heat treatment. Typically at dawn of a hot summer day, land plants need precise molecular thermometers to sense harmless increments in the ambient temperature to timely develop a heat-shock response (HSR) and accumulate protective heat shock proteins (Hsps), in anticipation of upcoming harmful temperatures at mid-day. Here, we found that the CNGCb gene from Physcomitrella patens and its Arabidopsis ortholog CNGC2, encode for a component of cyclic nucleotide gated Ca2+ channels acting as the primary thermosensors of land plant cells. Disruption of CNGCb or CNGC2 produced a hyper-thermosensitive phenotype, giving rise to a HSR and acquired thermotolerance at significantly milder heat-priming treatments than in wild type plants. In an aequorin-expressing moss, CNGCb loss-of-function caused altered Ca2+ signaling and a sustained Ca2+ influx. Patch clamp recordings on moss protoplasts showed the presence of three distinct thermo-responsive Ca2+-channels in wild type cells. Deletion of CNGCb led to a total absence of one, and it increased the open probability of the remaining two thermo-responsive Ca2+ channels. Thus, both in Arabidopsis and moss, CNGC2 and CNGCb are expected to form with other related CNGCs, heteromeric Ca2+ channels in the plasma membrane that respond to mild increments in the ambient temperature by triggering an optimal HSR, leading to the onset of plant acquired thermotolerance. The WT moss tissues were heat-shocked for a half an hour at 34°C and 38°C and CNGCb at 25and 34°C followed by liquid nitrogen freezing. Total RNA was isolated using RNeasy Mini Kit (QIAGEN, Hilden, Germany) and two biological replicate samples for each treatment, were extracted. An Agilent-certified microarray service lab (MOgene, LC, St. Louis, MO, USA) was used to verify the integrity of the RNA and perform the microarray experiments. Two biological replicates were performed.

Dataset Information

Gonadotropin-releasing hormone-1 neuronal activity is independent of cyclic nucleotide-gated channels.

Publications

Gonadotropin-releasing hormone-1 neuronal activity is independent of cyclic nucleotide-gated channels.

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