IS THE
HEARING LOSS IN ELDERLY PERSONS AN EFFECT OF THE NEUROTOXICITY OF EXCITATORY
NEUROTRANSMITTERS?
By Renato Cocchi MD.
The
hearing loss in elderly persons is primarily a sensory-neural hypoacousia, and one of its variations is the so-called presbiacousia. This last seems an ineluctable fate of a
part of elderly persons, of which little is known and for which there is a few
to do.
The presbiacousia is quite surely due to a toxicity effect by
excitatory neurotransmitters.
The
elements to support this hypothesis are:
- Not all
the elderly, go to meet sensory-neural hypoacousia (50% in 75 years old people);
- In the
elderly there is a known lowering of the stress threshold, and this implies the
GABA-glutamate pathways, with decreasing of the type A GABAergic
inhibition, increasing of the type B GABAergic
inhibition, lowering of GAD activity followed by glutamate-GABA unbalance, even
only for reduction of the turnover of the GABA;
- The
continuous exposure to the noise produces sensory-neural hypoacousia;
- In
certain depressive forms one symptom is the lowering of the threshold for the
noise, a fact that presupposes a glutamergic sensory
hypersensitivity, being known that the glutamate is the prevailing
neurotransmitter of the afferent nerves;
- The
tinnitus is typical of the elderly or of the post-traumatic stress syndrome,
then involved in the relationship between the auditory threshold and stress;
- In the
autism, where recently GABA gained a main role (News6.htm), there is nearly
always a hypersensitivity to noise ( the child closes
his ears with his hands);
- In the presbiacousia the auditory deficit is fluctuating, then there is a link with something that is fluctuating in
its turn. The stress amount, as sum of different contemporary stress, has these
characteristics.
- If the presbiacousia is related to stress and to an increasing
activity of excitotoxic neurotransmitters following a
deficit of GABA on type A receptors, a preventive work
to keep into balance these neurotransmitters by drugs, should have to start
early and to keep into action for a long time.
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