Progesterone regulation of GABA(A) receptor plasticity in adult rat supraoptic nucleus

Valérie S. Fénelon, Allan E. Herbison
European Journal of Neuroscience. 2000-05-01; 12(5): 1617-1623
DOI: 10.1046/j.1460-9568.2000.00053.x

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Marked plasticity in GABAA receptor signalling occurs in adult oxytocin neurons
of the supraoptic nucleus (SON) through the modulation of GABAA receptor alpha
subunits during pregnancy. The present studies were undertaken to examine the
potential mechanisms underlying this plasticity. In vivo microdialysis
experiments in conscious rats revealed that no significant changes in
extracellular GABA concentrations occurred within the SON over the last two days
of pregnancy and the time of parturition itself. In situ hybridization studies
examined the effects of gonadal steroid manipulation upon the GABAA receptor
subunits expressed by SON neurons (alpha1, alpha2, beta2 and gamma2 subunits) and
demonstrated that cellular levels of the alpha1 subunit were increased following
8 days oestrogen and progesterone treatment. Estrogen alone or allopregnanolone,
the progesterone derivative, had no effect on alpha1 subunit mRNA expression in
the SON. Immunocytochemical experiments demonstrated progesterone receptors in
many neural populations but not within the SON of late pregnant rats. These
studies indicate that alterations in endogenous GABA release within the SON are
unlikely to be responsible for the GABAA receptor plasticity exhibited by
oxytocin neurons in late pregnancy. Rather, data demonstrate that the fluctuating
concentrations of progesterone during pregnancy act indirectly on SON neurons to
modulate alpha1 subunit mRNA expression. Together, these experiments provide
evidence for the ligand-independent induction of GABAA receptor plasticity in the
adult brain by progesterone.


Auteurs Bordeaux Neurocampus