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This Article Full Text Full Text (PDF) All Versions of this Article: 586/7/1903    most recent jphysiol.2008.150706v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Barrière, G. Articles by Bertrand, S. S. PubMed PubMed Citation Articles by Barrière, G. Articles by Bertrand, S. S. Related Collections Neuroscience

¹ Université Victor Segalen Bordeaux 2, Université Bordeaux 1, CNRS UMR 5227, Mouvement Adaptation Cognition, Bordeaux, France

In the present study, we investigated the modulation of short-term depression (STD) at synapses between sensory afferents and rat motoneurons by serotonin, dopamine and noradrenaline. STD was elicited with trains of 15 stimuli at 1, 5 and 10 Hz and investigated using whole-cell voltage-clamp recordings from identified motoneurons in the neonatal rat spinal cord in vitro. STD was differentially modulated by the amines. Dopamine was effective at all stimulation frequencies, whereas serotonin affected STD only during 5 and 10 Hz stimulus trains and noradrenaline during 1 and 5 Hz trains. Dopamine and serotonin homogenized the degree of depression observed with the different stimulation modalities, in contrast to noradrenaline, which amplified the rate differences. The different modulatory profiles observed with the amines were partly due to GABAergic interneuron activity. In the presence of GABA_A and GABA_B receptor antagonists, the rate and/or kinetics of STD did not vary with the stimulation frequency in contrast to the control condition, and noradrenaline failed to alter either synaptic amplitude or STD, suggesting indirect actions. Dopamine and serotonin strongly decreased STD and converted depression to facilitation at 5 and 10 Hz during the blockade of the GABAergic receptors in 50% of the neurons tested. Altogether, these results show that STD expressed at sensorimotor synapses in the neonatal rat not only is a function of the frequency of afferent firing but also closely depends on the neuromodulatory state of these connections, with a major contribution from GABAergic transmission.

(Received 3 January 2007; accepted after revision 5 February 2008; first published online 7 February 2008)
Corresponding author S. S. Bertrand: Université Victor Ségalen (Bordeaux 2) Zone Nord, Bt. 2A/B; 146, rue Léo Saignat, 33076 Bordeaux cedex, France.  Email: sandrine.bertrand{at}u-bordeaux2.fr