Modulation of motoneuronal activity mediated by voltage-dependent conductances of nonspiking neurons in the leech nervous system

LORENA RELA; LIDIA SZCZUPAK

San Diego, CA, Estados Unidos

Congreso; Society for Neuroscience Annual Meeting; 2004

Society for Neuroscience

Non-spiking neurons codify signals in the nervous system through graded changes in membrane potential, which can only be detected recording cells intracellularly. The leech nervous system has the advantage of allowing to clearly identify neuron types from one animal to another. The NS (non-spiking) neurons are a pair of non-spiking neurons that can be identified in each midbody ganglion of the leech nervous system.We have previously shown that NS neurons are profusely connected to motoneurons through electrical synapses and that they are central elements in a circuit that regulates the coordinated activity of motoneurons. We also showed that NS neurons have voltage-activated membrane conductances that depend on extracellular sodium and calcium.The present work evaluates the role of these voltage-activated conductances on the influence that NS neurons exert on the activity of motoneurons.The experiments were performed in isolated midbody ganglia of Hirudo medicinalis under constant superfusion and the electrical activity of neurons was studied by means of intracellular and extracellular electrodes.Our experiments show that treatments that altered the manifestation of the voltage-activated conductances also altered the dynamics of the effect that NS neurons exerted upon motoneuronal activity.We postulate that the voltage-activated conductances present in these non-spiking neurons shape their synaptic outputs.