title: The activity of leech motoneurons during motor patterns is regulated by intrinsic properties and synaptic inputs.
abstract: The activity of motoneurons during motor patterns depends on their intrinsic properties and on synaptic inputs. This study analyzed the properties of two leech motoneurons: the excitors of dorsal longitudinal muscles (DE-3) and of dorsal and ventral longitudinal muscles (MN-L) in basal conditions (normal and high Mg²⁺ saline) and during crawling. The voltage-current relationships in DE-3 and MN-L were similar. The curves exhibited the largest slope around resting potential, showed marked inward and outward rectification, and were not affected by high Mg²⁺. In response to 5-s pulses, DE-3 exhibited a fast initial adaptation, a slow recovery and a very slow late adaptation. High Mg²⁺ abolished the initial high frequency. The frequency-voltage relationship for the rest of the response was highly similar in normal and in high Mg²⁺ saline. MN-L exhibited a minor initial adaptation and then fired steadily. High Mg²⁺ diminished the frequency-voltage relationship. During crawling DE-3 and MN-L fired in phase and their frequency-voltage curves overlapped with the lower end of the curves obtained in basal conditions. The results suggest that the activity of these motoneurons during crawling was regulated, to a large extent, by synaptic inputs.
authors.affiliation: Departamento de Fisiología y Biología Molecular, FCEN-UBA, IFIBYNE UBA-CONICET, Buenos Aires, Argentina.
authors.forename: C
authors.initials: C
authors.lastname: Bernardo Perez-Etchegoyen
authors.forename: Rodrigo J
authors.initials: RJ
authors.lastname: Alvarez
authors.forename: Mariano J
authors.initials: MJ
authors.lastname: Rodriguez
authors.forename: Lidia
authors.initials: L
authors.lastname: Szczupak
mesh_terms: D000818:Animals; D007865:Leeches / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D009043:Motor Activity / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology*; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*