Inhibitory effects of catecholamines in canine cardiac Purkinje fibers

1976 ◽  
Vol 231 (5) ◽  
pp. 1415-1420 ◽  
Author(s):  
P Posner ◽  
EL Farrar ◽  
CR Lambert
Keyword(s):  
Negative Response ◽  
Chronotropic Effect ◽  
Inhibitory Effects ◽  
Purkinje Fibers ◽  
Spontaneous Rate ◽  
Negative Chronotropic Effect ◽  
Cardiac Purkinje Fibers ◽  
Wide Range ◽  
Low Levels

The effect of catecholamines over a wide range of concentrations was studied on 42K uptake and efflux, as well as on spontaneous rate in canine cardiac Purkinje fibers. Low levels of catecholamines (less than 10(-10) M epinephrine; less than 10(-9) M norepinephrine) decreased automaticity. This negative chronotropic effect was blocked by phentolamine and mimicked by phenylephrine. These low levels of epinephrine and norepinephrine also inhibited 42K uptake by Purkinje fibers but had no effect on 42K efflux. The inhibition of 42K uptake was blocked by phentolamine and verapamil and mimicked by phenylephrine. The data indicate an alpha-receptor-mediated negative response of rate and 42K uptake to low levels of catecholamine. The end result is discussed in terms of a competitive increase in the influx of Ca2+ rather than Na+ and an indirect inhibition of the Na+-K+ pump.

α1a-Adrenergic receptor mediated positive chronotropic effect in right atria isolated from rats

1994 ◽  
Vol 72 (12) ◽  
pp. 1574-1579 ◽  
Author(s):  
Anthony P. Williamson ◽  
Ernst Seifen ◽  
Jon P. Lindemann ◽  
Richard H. Kennedy
Keyword(s):  
Adrenergic Receptor ◽  
Response Curve ◽  
Male Rats ◽  
Chronotropic Effect ◽  
Rightward Shift ◽  
Spontaneous Rate ◽  
Negative Chronotropic Effect ◽  
Right Atria ◽  
Concentration Response Curve ◽  
Positive Chronotropic Effect

Experiments in right atria isolated from adult male rats were designed to determine which of the α1-adrenergic receptor (α1-AR) subtypes are involved in the positive chronotropic effect of phenylephrine, an α1-AR agonist. Chloroethylclonidine (CEC), an irreversible α1b-, α1c-, and α1d-AR antagonist, did not alter the efficacy or potency of phenylephrine; however, CEC did elicit a concentration-dependent negative chronotropic effect and reduce the absolute maximum spontaneous rate observed in the presence of phenylephrine. WB4101, a competitive α1a- and α1c-AR-selective antagonist, did not alter basal spontaneous rate or the efficacy of phenylephrine, but it did produce a significant rightward shift of the phenylephrine concentration–response curve. Phenoxybenzamine, an irreversible nonselective α-AR antagonist, elicited a concentration-dependent negative chronotropic effect, a significant rightward shift of the phenylephrine concentration–response curve, and a reduction in the efficacy of phenylephrine. The chronotropic action of the β-adrenergic agonist isoproterenol was not affected by CEC, WB4101, or phenoxybenzamine. These data suggest that the positive chronotropic effect of α1-adrenergic agonists in rat right atria is mediated via stimulation of α1a-ARs.Key words: α1-adrenergic receptor subtypes, chloroethylclonidine, WB4101, phenylephrine, right atria (rat).

scholarly journals Electrophysiological analysis of the negative chronotropic effect of endothelin‐1 in rabbit sinoatrial node cells

2001 ◽  
Vol 537 (2) ◽  
pp. 467-488 ◽  
Author(s):  
Kageyoshi Ono ◽  
Haruko Masumiya ◽  
Aiji Sakamoto ◽  
Georges Christé ◽  
Toshinori Shijuku ◽  
...  
Keyword(s):  
Sinoatrial Node ◽  
Chronotropic Effect ◽  
Endothelin 1 ◽  
Negative Chronotropic Effect ◽  
Electrophysiological Analysis ◽  
Sinoatrial Node Cells ◽  
Rabbit Sinoatrial Node

Differential Effects of Halothane and Isoflurane on Contractile Force and Calcium Transients in Cardiac Purkinje Fibers

1994 ◽  
Vol 80 (6) ◽  
pp. 1360-1368 ◽  
Author(s):  
David F. Stowe ◽  
Juraj Sprung ◽  
Lawrence A. Turner ◽  
John P. Kampine ◽  
Zeljko J. Bosnjak
Keyword(s):  
Contractile Force ◽  
Calcium Transients ◽  
Purkinje Fibers ◽  
Differential Effects ◽  
Cardiac Purkinje Fibers

scholarly journals Acceptance threshold theory can explain occurrence of homosexual behaviour

2015 ◽  
Vol 11 (1) ◽  
pp. 20140603 ◽  
Author(s):  
Katharina C. Engel ◽  
Lisa Männer ◽  
Manfred Ayasse ◽  
Sandra Steiger
Keyword(s):  
Animal Species ◽  
Reproductive Potential ◽  
Search Time ◽  
Same Sex ◽  
Burying Beetles ◽  
Acceptance Threshold ◽  
Threshold Theory ◽  
Wide Range ◽  
Low Levels ◽  
Perceived Costs

Same-sex sexual behaviour (SSB) has been documented in a wide range of animals, but its evolutionary causes are not well understood. Here, we investigated SSB in the light of Reeve's acceptance threshold theory. When recognition is not error-proof, the acceptance threshold used by males to recognize potential mating partners should be flexibly adjusted to maximize the fitness pay-off between the costs of erroneously accepting males and the benefits of accepting females. By manipulating male burying beetles' search time for females and their reproductive potential, we influenced their perceived costs of making an acceptance or rejection error. As predicted, when the costs of rejecting females increased, males exhibited more permissive discrimination decisions and showed high levels of SSB; when the costs of accepting males increased, males were more restrictive and showed low levels of SSB. Our results support the idea that in animal species, in which the recognition cues of females and males overlap to a certain degree, SSB is a consequence of an adaptive discrimination strategy to avoid the costs of making rejection errors.

Breeding and Mating Systems of Australian Proteaceae

1998 ◽  
Vol 46 (4) ◽  
pp. 421 ◽  
Author(s):  
Ross L. Goldingay ◽  
Susan M. Carthew
Keyword(s):  
Fruit Development ◽  
Mating Systems ◽  
Pollen Deposition ◽  
Genetic Studies ◽  
The Past ◽  
Wide Range ◽  
The Family ◽  
Self Compatibility ◽  
Low Levels ◽  
Key Events

There has been a significant increase in the number of studies investigating plant breeding and mating systems over the past 10 years. The family Proteaceae, in particular, has dominated such research conducted in Australia. Thus it is now timely to present a critical review of the breeding and mating systems of the Australian Proteaceae. It is hoped that this will stimulate further research. The review covers key events between pollen deposition on stigmas through to fruit set. The genus Banksia, although not the most diverse of the family, has received a disproportionate amount of attention. It has featured in nine published studies of self-compatibility compared to 13 studies spanning the other 45 genera and has featured in eight genetic studies of the mating system compared to just two on other genera. Few studies have assessed the timing of stigma receptivity despite the intriguing situation in most Proteaceae of auto-deposition of self-pollen on or near stigmas at anthesis. Studies suggest that stigmas are not receptive until 0.5–4 days after anthesis. Banksia species appear to show low levels of self-compatibility although one subspecies shows high levels of selfing and evidence of selective fruit development. Self-compatibility may be more common in other genera, although a dearth of studies precludes generalisation. Assessment of mating systems indicates almost complete outcrossing for most species, lending support to the idea of selective fruit development. It is clear that many further studies of all topics are required but particularly across a wide range of genera because many have not been studied at all.

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