Mammals and birds have a specialized cardiac atrioventricular conduction system enabling rapid activation of both ventricles. This system may have evolved together with high heart rates to support their endothermic state (warm-bloodedness) and is seemingly lacking in ectothermic vertebrates from which first mammals then birds independently evolved. Here, we studied the conduction system in crocodiles (Alligator mississippiensis), the only ectothermic vertebrates with a full ventricular septum. We identified homologues of mammalian conduction system markers (Tbx3-Tbx5, Scn5a, Gja5, Nppa-Nppb) and show the presence of a functional atrioventricular bundle. The ventricular Purkinje network, however, was absent and slow ventricular conduction relied on trabecular myocardium, as it does in other ectothermic vertebrates. We propose the evolution of the atrioventricular bundle followed full ventricular septum formation prior to the development of high heart rates and endothermy. In contrast, the evolution of the ventricular Purkinje network is strongly associated with high heart rates and endothermy.

• MeSH
• aligátoři a krokodýli embryologie   genetika   fyziologie   MeSH
• embryo nesavčí metabolismus   MeSH
• Hisův svazek embryologie   metabolismus   fyziologie   MeSH
• hybridizace in situ MeSH
• mezikomorová přepážka embryologie   metabolismus   fyziologie   MeSH
• modely kardiovaskulární MeSH
• převodní systém srdeční embryologie   fyziologie   MeSH
• proteiny T-boxu genetika   metabolismus   MeSH
• Purkyňova vlákna embryologie   metabolismus   fyziologie   MeSH
• srdce embryologie   fyziologie   MeSH
• srdeční frekvence genetika   fyziologie   MeSH
• srdeční komory embryologie   metabolismus   MeSH
• vývojová regulace genové exprese MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

To understand the contribution of potassium (K+) channels, particularly ?-dendrotoxin (D-type)-sensitive K+ channels (Kv.1, Kv1.2 or Kv1.6 subunits), to the generation of neuronal spike output we must have detailed information of the functional role of these channels in the neuronal membrane. Conventional intracellular recording methods in current clamp mode were used to identify the role of ?-dendrotoxin (?-DTX)-sensitive K+ channel currents in shaping the spike output and modulation of neuronal properties of cerebellar Purkinje neurons (PCs) in slices. Addition of ?-DTX revealed that D-type K+ channels play an important role in the shaping of Purkinje neuronal firing behavior. Repetitive firing capability of PCs was increased following exposure to artificial cerebrospinal fluid (aCSF) containing ?-DTX, so that in response to the injection of 0.6 nA depolarizing current pulse of 600 ms, the number of action potentials insignificantly increased from 15 in the presence of 4-AP to 29 action potentials per second after application of DTX following pretreatment with 4-AP. These results indicate that D-type K+ channels (Kv.1, Kv1.2 or Kv1.6 subunits) may contribute to the spike frequency adaptation in PCs. Our findings suggest that the activation of voltage-dependent K+ channels (D and A types) markedly affect the firing pattern of PCs.

• MeSH
• draslíkové kanály izolace a purifikace   metabolismus   MeSH
• elektrofyziologie metody   přístrojové vybavení   MeSH
• financování organizované využití   MeSH
• kůra mozečku fyziologie   metabolismus   MeSH
• peptidy fyziologie   metabolismus   MeSH
• potkani Sprague-Dawley fyziologie   metabolismus   MeSH
• Purkyňova vlákna fyziologie   metabolismus   MeSH