cell to cell communication

Acetylcholine was discovered by Otto Loewi and Henry Dale, but they called it vagusstoff

Mediator

-          A mediator is a chemical, peptide or protein that conveys information from one cell to another

-          When in response to a stimulus of some kind, a mediator is released and produces a particular biological response

-          Experimental Criteria that establish a substance as a mediator are:

1.    It is released from cells in sufficient amounts to produce a biological action on target cells within an appropriate time frame

2.    Application of an authentic sample of the mediator reproduces the original biological effect

3.    Interference with the synthesis, release or action (e.g. Using receptor selective drugs, enzyme inhibitors, knock-down or knock-out techniques) ablates or modulates the original biological response

The 5 main types of intercellular communication are: contact dependent, paracrine, autocrine, synaptic, endocrine

Paracrine signaling

-           Extracellular signal mediator acts locally

-           Mediators are stored in vesicles or are synthesized on demand

Autocrine signaling

-          A cell produces a substance that affects itself.

Contact-dependent signaling: Can be the shortest range of cellular communication as it requires direcct physical contact between cells

Neuronal signaling

-          Uses synapses

-          Restricts signaling to specific target cells

-          Synapses may be short od long distances from neuronal cell bodies

-          Chemical mediators of neuronal signaling are neurotransmitters

Synthesis of chemical mediators occurs in 2 ways

1.    Synthesis of small molecular mediators is regulated by specific enzymes. Which mediators a cell produces will depend on which enzymes are active

2.    Synthesis of peptides is regulated by transcription. Which mediators a cell produces is dependent on which genes are active (cells can produce multiple types of mediator and secretory vesicles can store more than one type of mediator)

Two groups of chemical mediators

-          Mediators which are pre-formed, stored in vesicles from which they are released by exocytosis. This allows for rapid communication and can include small molecule mediators and peptides

-          Mediators produced on demand and released by diffusion or constitutive secretion. This takes longer to act