There has been a great search for endogenous benzodiazepines, or endozepines (endo = endogenous and zepines from benzodiazepines).
The idea is that if such a highly specific site is present on the receptor then there must be an endogenous ligand for that site (i.e. mother nature did not create the site for the benefit of the pharmaceutical industry).
By analogy, a similar search for an endogenous morphine in the 1970's led to the discovery of the endorphin family of neuropeptides (endorphin = endogenous morphine) .
Despite a massive amount of research the question of an endozepine still remains uncertain.
"Endozepine-like-activity" has been extracted from rat and human brains but its exact composition remains elusive.
Thus, we remain dependent on the benzodiazepines for relief from life's little stresses.
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death of the endozepines?
In the 21 October, 1999 issue of Nature it is reported that mice, homozygous for a mutation in the benzodiazepine binding site of the alpha subunit of the GABAa receptor, seem quite normal.
The authors hypothesis that if there were such a thing as an endozepine then one might have expected that these mice would be more alert or sleep less.
They found no hint of such behavior and a suggest that maybe mother nature really did create the site for the delight of pharmacologist!