Responses to phenethylamines and nicotine and histology of turtle atria

Abstract

Epinephrine (E), norepinephrine (NE), tyramine (T) and nicotine were tested at various dosage levels on different atrial regions of the heart of the eastern painted turtle, Chrysemys picta picta (Schneider), and the median effective dose determined. The three phenethylamines acted according to the following pattern in their effect on rate increase, amplitude increase, and inhibition of tonus waves: E > NE > T, except for amplitude increase in the left atrium and tonus wave inhibition in both atria, where E and NE were equal. The right sino-atrium and left atrium differed in sensitivity to the drugs. The various responses, including treppe, are consonant with the theory of the release from the tissues of a potentiating substance and a depressing substance. Histological stains for chromaffin tissue, a possible source of potentiating substance, were negative, but a differentially stained type of cardiac muscle, a possible conducting tissue, is present in regions of the sinus venosus and both atria and at the base of the interatrial septum.

Contraction of atrial smooth muscle reduces cardiac output in perfused turtle hearts

“…The pharmacology and basic contractile properties of the atrial smooth muscle were well detailed in the early investigations. For instance, the smooth-muscle-dependent tonus contraction is potentiated by vagal stimulation, histamine and pituitary extract, but inhibited by sympathetic stimulation with adrenaline (Bottazzi and Grünbaum, 1899;Dimond, 1959;Fano, 1887;Fano and Fayod, 1888;Gault, 1917;Gruber, 1920aGruber, ,b, 1921Gruber, , 1927Gruber, , 1934Gruber and Markel, 1918a,b;Sollmann and Rossides, 1927). However, little consensus was reached regarding its functional role, although implications for electrical conduction or strengthening atrial contraction were suggested (Meek, 1927;Shaner, 1923).…”

Smooth Muscle in Cardiac Chambers is Common in Turtles and Extensive in the Emydid Turtle,Trachemys scripta

“…In the late 19th century, slow wave contractions (the so‐called tonus waves) were observed in isolated atrial preparations from European pond turtles ( Emys orbicularis ) (Fano, ; Fano and Fayod, ; Bottazzi, ). The tonus waves were soon attributed to the conspicuous amounts of smooth muscle in the atria (Rosenzweig, ; Bottazzi, ), but despite a few decades of relatively intense research into its pharmacological properties (Fano, ; Fano and Fayod, ; Bottazzi and Grünbaum, ; Gault, ; Gruber and Markel, , ; Gruber, , , , ; Sollmann and Rossides, ; Gruber, ; Dimond, ), the scientific interest in the atrial smooth muscle waned after the 1920s. As part of other studies, we also observed the tonus waves (Galli et al ., ; Joyce et al ., ), and with a revived curiosity into their functional role, we recently demonstrated that the atrial smooth muscle may provide a powerful means to regulate ventricular filling and hence cardiac stroke volume (Joyce et al ., ).…”

“…The European‐based discoverers of the atrial smooth muscle universally employed the Emydid turtle E. orbicularis (formerly Emys europaea ) (e.g., Fano, ; Bottazzi and Grünbaum, ; Fano and Bodano, ; Rosenzweig, ; Oinuma, ), but were soon followed by North American studies on a wealth of other turtle species in the Emydid family, including Trachemys scripta (Laurens, ; Gruber and Markel, , ; Pereira, ; Sollmann and Rossides, ; Robb, ; Dimond, ). There are additional vague descriptions of tonus waves in atria from Chelydra serpentina (snapping turtles; Chelydridae); very little detail is given by Pereira (Pereira, ), where data are indiscriminately combined with findings in Emydid turtles, while Blinks and Koch‐Weser () cite their own unpublished observations about this species.…”

Absence of atrial smooth muscle in the heart of the loggerhead sea turtle (Caretta caretta): a re-evaluation of its role in diving physiology

“…Smooth muscle was first identified in ex vivo atrial preparations of the European pond turtle ( Emys orbicularis ), distinguishable by its production of characteristic slow tonus-wave contractions that were clearly distinct from the normal rapid contractions of cardiac muscle (Fano, 1886). These tonus contractions were repressed by sympathetic stimulation with adrenaline, and potentiated by vagal stimulation, histamine, and pituitary extract (Bottazzi and Grünbaum, 1899; Dimond, 1959; Gault, 1917; Gruber, 1920; Gruber and Markel, 1918; Sollmann and Rossides, 1927). Early histological studies described a dense layer of smooth muscle lining the luminal side of the atrial wall, originating in the sinus venosus and pulmonary veins, and continuing into the ventricle where its distribution becomes sparse (Laurens, 1913; Shaner, 1923).…”