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Journal of Neuroendocrinology (1)
de Monvel, Jacques Boutet (2)
Bertram, Richard (1)
Caberlotto, Elisa (1)
Egli, Marcel (1)
Freeman, Marc E. (1)
Gerber, Urs (1)
Gonzalez-Iglesias, Arturo E. (1)
Michel, Vincent (1)
Petit, Christine (1)
Sirzen-Zelenskaya, Alexandra (1)
Year of Publication
Prolactin induces a hyperpolarizing current in rat paraventricular oxytocinergic neurons
Gonzalez-Iglesias, Arturo E.
Freeman, Marc E.
Journal of Neuroendocrinology
Prolactin and oxytocin are important reproductive hormones implicated in several common adaptive functions during pregnancy, pseudopregnancy and lactation. Recently, extracellular recordings of supraoptic neurons have shown that prolactin may modulate electrical activity of oxytocinergic neurons. However, no study has been conducted to establish whether prolactin directly influences this activity in oxytocinergic paraventricular neurons. Here we addressed this question by studying the effects of prolactin on the electrical activity and voltage-current relationship of identified paraventricular neurons in rat brain slices. Whole-cell recordings were obtained and neurons were classified on the basis of their morphological and electrophysiological fingerprint (magnocellular or parvicellular) and neuropeptide phenotype (oxytocinergic or non-oxytocinergic). We report that prolactin elicited a hyperpolarizating current in 37% of the neurons in this nucleus, of which the majority (67%) were identified as putative magnocellular oxytocin neurons and the reminder (33%) were regarded as oxytocin-negative, parvicellular neuroendocrine neurons. Our results suggest that, in addition to the well-established negative feedback loop between prolactin-secreting lactotrophs and dopaminergic neurons in the arcuate nucleus, an inhibitory feedback loop also exists between lactotrophs and oxytocinergic paraventricular neurons.
Oxytocin; prolactin; paraventricular nucleus; whole-cell recordings; immunocytochemistry, feedback
Coupling of the mechanotransduction machinery and F-actin polymerization in the cochlear hair bundles
Mechanoelectrical transduction (MET), the conversion of mechanical stimuli into electrical signals operated by the sensory cells of the inner ear, enables hearing and balance perception. Crucial to this process are the tip-links, oblique fibrous filaments that interconnect the actin-filled stereocilia of different rows within the hair bundle, and mechanically gate MET channels. In a recent study, we observed a complete regression of stereocilia from the short and medium but not the tall row upon the disappearance of the tip-links caused by the loss of one of their components, cadherin-23, or of one of their anchoring proteins, sans, in the auditory organs of engineered mutant mice. This indicates the existence of a coupling between the MET and F-actin polymerization machineries at the tips of the short and medium stereocilia rows in cochlear hair bundles. Here, we first present our findings in the mutant mice, and then discuss the possible effects of the tip-link tension on stereocilia F-actin polymerization, acting either directly or through Ca2+-dependent mechanisms that involve the gating of MET channels.
hair cell; hair bundle; stereocilia; mechanoelectrical transduction (MET); tip-link; sans protein; actin polymerization
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