First formal experiment in endocrinology:

 

Arnold Adolph Berthold, 1849—Studied roosters

           

Effects of prepubertal castration of male chick (used to make capons—more tender meat):

      reduces secondary male appearance—

      also affects behavior—

 

Berthold wanted to know if these extensive effects were dependent on neural connection to the testes. [There was a general appreciation of the role of nerves in functionally connecting different parts of the body, even though neurons had not yet been identified]

 

Additional results:

1) on autopsy the transplanted testis had re-established a blood supply, but not a neural supply

      implication—

 

2) reimplanted or transplanted testis was also approximately 2 times larger than normal:

      implication—

 

Question: So, hormones affect behavior (the Mind); Can behavior (the Mind) affect hormones?

 

Anonymous report to Nature: Self-report on beard growth of an isolated lighthouse keeper

[Nature 226:869-870, 1970]

      Bioassay—

What is a hormone? Partial Definition: An example of an intercellular chemical signal—a chemical substance, a molecule, that is secreted by one cell of the body and modifies the function of another cell of the body.

 

Distinction between a hormone and a neurotransmitter:

 

 

 

Neurotransmitter

 

Hormone

 

 

 

Chemical Structure

 

 

 

 

 

 

 

 

 

 

 

 

 

Source (cell type)

 

 

 

 

 

Target

 

 

 

 

 

 

 

 

 

 

 

Mode of delivery to target

 

 

 

 

 

 

 

 

 

 

Most hormones are systemic:

 

What determines which cells are a target for a systemic hormone?

 

Why have hormones for intercellular signaling instead of neurotransmitters?