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I am reading this and this where I am considering this sentence

[N]o baseline parasympathetic innervation [in transplanted heart].

Does this sentence imply that the heart work then in full sympaticus all the time? Probably, through altered systems, but still. At least the regulation of blood pressure strongly supports this, here for the generic medication plan.

Does transplanted heart have full sympaticus without medication?

Notification of terminology. I tend to use overloading in writing. For instance, I can say that there is sympathetic and parasympathetic supply to the heart i.e. innervations of S and PS through endocrine system to the heart.

I am not yet completely sure how the recipient's body can target the alpha and beta receptors of donors in heart. Are there any variations of these receptors? If yes, then the effect of sympathetic stimulation would also differ from the original stimulation. So full sympaticus (or original) may not be present. The new stimulation may lead to greater or smaller activation of sympaticus.

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The parasympathetic supply to the heart is by nerves and that is truncated during surgery as pointed out.

The sympathetic supply to the heart is by two means:

  1. Through sympathetic nerves from the sympathetic trunk
  2. From the adrenal medulla which secretes both adrenaline and nor-adrenaline directly into the blood stream

The heart contains the beta receptors for the sympathetic system, especially the ventricles and nodes (SA) and conducting fibers. These receptors respond to the presence of adrenaline and nor-adrenaline in blood. Thus the sympathetic response is preserved while the parasympathetic responce is lost.

There is a minimal level of nor-epinephrine in blood at all times which thus influences the heart.

Receptors in Heart: Receptors in Heart

The heart contains adrenergic (sympathetic) and cholinergic (Parasympathetic) receptors. When the heart is transplanted, the donor heart also contains the same receptors. The only thing missing are the nerves.

The sympathetic system does not suffer as much as the parasympathetic system, because of the adrenal medulla which secretes the nor-epinephrine (same as nor-adrenaline) into the blood, which upon reaching the heart can stimulate the beta receptors on the heart.

There is no organ which releases acetyl-choline into blood, (fortunately, as such a release would be disastrous leading to shock and rigor, possibly death). So the parasympathetic receptors in the heart do not receive any stimuli.

Edit 1: In response to your edit, yes there are polymorphisms in all receptors. But the structure of adrenaline and nor-adrenaline are pretty much constant. This means that the donor heart will be at a similar level of sympaticus as it was in the donor when (s)he was alive. Although this will not be the same as the recipients pre-surgery sympaticus state of the now removed heart.

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    $\begingroup$ Yes, adrenal medulla is kind of a sympathetic endocrine system, stimulating the whole body at times of need $\endgroup$ – One Face Jan 6 '15 at 9:50
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    $\begingroup$ I think I gave you the wrong idea. I will explain further in the answer $\endgroup$ – One Face Jan 6 '15 at 11:16
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    $\begingroup$ I don't understand your comment. There are no nerves to heart and thus no action potential in generated in any nerves. The receptors are in the heart muscle cells and conducting fibers. The effects are as described above $\endgroup$ – One Face Jan 6 '15 at 14:20
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    $\begingroup$ In your definitions, is there sympathetic supply to heart? I tend to overload terms and say that there is both S and PS supply to heart through endocrine system. $\endgroup$ – Léo Léopold Hertz 준영 Jan 8 '15 at 5:42
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    $\begingroup$ Yes, maybe that's why I was confused. I also confused myself with the term 'action potential' I forgot about the muscle action potential. Did that answer your question? $\endgroup$ – One Face Jan 8 '15 at 9:46

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