Electrophysiological differences in cholinergic signaling between the hearts of summer and winter frogs (Rana temporaria)статья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 11 сентября 2018 г.
Аннотация:The striking seasonal difference in sensitivity of frog cardiac muscle to
acetylcholine or stimulation of parasympathetic nervous fibers has been noted
almost a century ago, although its electrophysiological basis has never been
revealed. The present study compares the effects of the muscarinic agonist
carbamylcholine chloride (CCh 10-8-10-5 M) on electrical activity in isolated
atrial and ventricular preparations from dormant frogs (Rana temporaria) caught
in January (winter-acclimatized, WA) and from active frogs caught in July
(summer-acclimatized, SA). Seasonal differences in the density of potassium
acetylcholine-dependent current (IKACh) were also studied in atrial and
ventricular myocytes from both summer and winter groups. In atrial myocardium,
CCh produced concentration-dependent shortening of action potentials (APs). CCh
concentration producing a 50% reduction of AP duration was lower in WA
(1.03 × 10-7 M) than SA atria (2.7 × 10-7 M). 10-6 M CCh induced drastic
reduction of AP amplitude rendering the tissue unexcitable in both WA or SA
atrial preparations. Ventricular preparations showed greater seasonal difference
in CCh sensitivity. While 10-6 M induced inexcitability in 50% of tested WA
preparations, in SA preparations even 10-5 M CCh was without effect. This
striking difference between cholinergic effects in SA and WA frog ventricle could
be explained by seasonal changes in the IKACh density. The density of IKACh
induced by 10-5 M CCh and measured at 0 mV was 14.4 ± 3.45 pA/pF in WA, but only
1.5 ± 0.4 pA/pF in SA atrial cells. In ventricular cells, the respective values
were 2.61 ± 0.56 and 0.71 ± 0.09 pA/pF. Thus, hibernating winter frog has a much
greater electrophysiological cholinergic response than active summer frog due to
up-regulation of IKACh.