The activation of the HPA axis is the endocrine measure of stress responsiveness that is initiated by corticotropin-releasing hormone (CRH). CRH exerts its effects via CRHR1 and CRH-R2 receptors coupled to the cAMP signaling system and this process involves transcription factor cAMP-responsive element-binding protein (CREB).This study investigated the role of CRH and the possible involvement of CREB in gene regulation of CRH receptor, under basal conditions and after stress application in the pituitary. We used wild type (wt +/+) controls and CRH knock-out (CRH-KO -/-) male mice. Using CRH-deficient mice, we were able to investigate the consequences of the lack of the CRH on the expression of CRH receptors and transcriptional regulation mediated by CREB. We estimated the effect of acute (IMO 1×) and repeated (IMO 7×) restraint stressors lasting 30 and 120 min on the expression of mRNA CREB, CRH-R1, and CRH-R2 by qPCR. We found very significant difference in the expression of these peptides under the effect of single and repeated stress in control and CRH-KO mice. Our results indicate that both CRH receptors and CREB might be involved in the regulation of stress response in the pituitary of mice. We propose that regulation of the stress response may be better understood if more were known about the mechanisms of CRH receptor signal transduction and involvement of CREB system.

• Klíčová slova
• Acute stress, CREB, CRH, CRH knock-out mice, CRH receptors, Repeated stress,
• MeSH
• akutní nemoc MeSH
• hormon uvolňující kortikotropin biosyntéza   nedostatek   MeSH
• hypofýza metabolismus   MeSH
• myši inbrední C57BL MeSH
• myši knockoutované MeSH
• myši MeSH
• protein vázající cAMP responzivní element biosyntéza   MeSH
• psychický stres metabolismus   psychologie   MeSH
• receptor CRF typu 1 MeSH
• receptory hormonu uvolňujícího kortikotropin biosyntéza   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• Creb1 protein, mouse MeSH Prohlížeč
• CRF receptor type 2 MeSH Prohlížeč
• hormon uvolňující kortikotropin MeSH
• protein vázající cAMP responzivní element MeSH
• receptor CRF typu 1 MeSH
• receptory hormonu uvolňujícího kortikotropin MeSH

Pituitary corticotrophs fire action potentials spontaneously and in response to stimulation with corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP), and such electrical activity is critical for calcium signaling and calcium-dependent adrenocorticotropic hormone secretion. These cells typically fire tall, sharp action potentials when spontaneously active, but a variety of other spontaneous patterns have also been reported, including various modes of bursting. There is variability in reports of the fraction of corticotrophs that are electrically active, as well as their patterns of activity, and the sources of this variation are not well understood. The ionic mechanisms responsible for CRH- and AVP-triggered electrical activity in corticotrophs are also poorly characterized. We use electrophysiological measurements and mathematical modeling to investigate possible sources of variability in patterns of spontaneous and agonist-induced corticotroph electrical activity. In the model, variation in as few as two parameters can give rise to many of the types of patterns observed in electrophysiological recordings of corticotrophs. We compare the known mechanisms for CRH, AVP, and glucocorticoid actions and find that different ionic mechanisms can contribute in different but complementary ways to generate the complex time courses of CRH and AVP responses. In summary, our modeling suggests that corticotrophs have several mechanisms at their disposal to achieve their primary function of pacemaking depolarization and increased electrical activity in response to CRH and AVP.NEW & NOTEWORTHY We and others recently demonstrated that the electrical activity and calcium dynamics of corticotrophs are strikingly diverse, both spontaneously and in response to the agonists CRH and AVP. Here we demonstrate this diversity with electrophysiological measurements and use mathematical modeling to investigate its possible sources. We compare the known mechanisms of agonist-induced activity in the model, showing how the context of ionic conductances dictates the effects of agonists even when their target is fixed.

• Klíčová slova
• action potentials, corticotrophs, corticotropin-releasing hormone, ion channels, vasopressin,
• MeSH
• akční potenciály * MeSH
• arginin vasopresin metabolismus   MeSH
• hormon uvolňující kortikotropin metabolismus   MeSH
• iontové kanály metabolismus   MeSH
• kortikotropní buňky metabolismus   fyziologie   MeSH
• kultivované buňky MeSH
• modely neurologické * MeSH
• myši inbrední C57BL MeSH
• myši MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• arginin vasopresin MeSH
• hormon uvolňující kortikotropin MeSH
• iontové kanály MeSH

Transgenic mice expressing the tdimer2(12) form of Discosoma red fluorescent protein under control of the proopiomelanocortin gene's regulatory elements are a useful model for studying corticotrophs. Using these mice, we studied the ion channels and mechanisms controlling corticotroph excitability. Corticotrophs were either quiescent or electrically active, with a 22-mV difference in the resting membrane potential (RMP) between the 2 groups. In quiescent cells, CRH depolarized the membrane, leading to initial single spiking and sustained bursting; in active cells, CRH further facilitated or inhibited electrical activity and calcium spiking, depending on the initial activity pattern and CRH concentration. The stimulatory but not inhibitory action of CRH on electrical activity was mimicked by cAMP independently of the presence or absence of arachidonic acid. Removal of bath sodium silenced spiking and hyperpolarized the majority of cells; in contrast, the removal of bath calcium did not affect RMP but reduced CRH-induced depolarization, which abolished bursting electrical activity and decreased the spiking frequency but not the amplitude of single spikes. Corticotrophs with inhibited voltage-gated sodium channels fired calcium-dependent action potentials, whereas cells with inhibited L-type calcium channels fired sodium-dependent spikes; blockade of both channels abolished spiking without affecting the RMP. These results indicate that the background voltage-insensitive sodium conductance influences RMP, the CRH-depolarization current is driven by a cationic conductance, and the interplay between voltage-gated sodium and calcium channels plays a critical role in determining the status and pattern of electrical activity and calcium signaling.

• MeSH
• akční potenciály účinky léků   MeSH
• AMP cyklický metabolismus   MeSH
• dibutyryl cyklický AMP farmakologie   MeSH
• hormon uvolňující kortikotropin farmakologie   MeSH
• iontové kanály metabolismus   MeSH
• kolforsin farmakologie   MeSH
• kortikotropní buňky účinky léků   metabolismus   fyziologie   MeSH
• kultivované buňky MeSH
• kyselina arachidonová farmakologie   MeSH
• membránové potenciály účinky léků   MeSH
• metoda terčíkového zámku MeSH
• myši inbrední C57BL MeSH
• myši transgenní MeSH
• sodík metabolismus   MeSH
• vápník metabolismus   MeSH
• vápníková signalizace účinky léků   MeSH
• vápníkové kanály - typ L metabolismus   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Intramural MeSH
• Názvy látek
• AMP cyklický MeSH
• dibutyryl cyklický AMP MeSH
• hormon uvolňující kortikotropin MeSH
• iontové kanály MeSH
• kolforsin MeSH
• kyselina arachidonová MeSH
• sodík MeSH
• vápník MeSH
• vápníkové kanály - typ L MeSH