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The Effect of Hormones

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  7. What is the role of hormones in the central nervous system?        7.2. Plasticity: Sexual steroids »shape« the brain

7.1. Neurosteroids: Balm for the mind

The steroid hormones produced in the brain include progesterone, and in particular various compounds closely related to progesterone. The manner in which they take effect is basically different from that of progesterone itself, classically affecting the progesterone receptor on the DNA inside the cell core. The Neurosteroids influence neurohormonal transmission from certain nerve cells to their subordinate nerve cells.
For this neurohormonal transmission, the nerve cells form special contacts with each other, so-called synapses, wherein an electrical signal is transformed into a chemical signal and then back again into an electrical signal. Small molecules, called neurotransmitters, wander through the tight synaptic cleft to the membrane of the subordinate nerve cell. There they dock on to specific receptors, with the effect of stimulating the post-synaptic cell.
Numerous different neurotransmitters are present in the central nervous system. One of these is gamma amino butyric acid (GABA). This molecule bonds with receptors serving as a sluice for chloride ions. Bonding with GABA opens the »sluice gates«, so that the chloride ions can stream into the plasma of the nerve cell. This induces a rise in the excitement threshold of the nerve cell. It is also explains the known calming and anxiety-reducing effect of progesterone (Fig. 10).



Abb. 10

Figure 10: Progesterone calms anxiety at nerve cell contacts (synapses): Neurosteroids, such as progesterone bond with certain GABA receptors, thereby enhancing the effect of GABA. This consists in channelling chloride ions into the subordinate nerve cell, thereby raising its excitement threshold. The result is a calming effect. This mechanism explains the anxiety-reducing and calming effect of progesterone.

  7. What is the role of hormones in the central nervous system?        7.2. Plasticity: Sexual steroids »shape« the brain
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Gerhard Leyendecker