Sensory and Motor Systems
Author: Graciela Ines Kearney | Email: graciela.kearney@gmail.com
Graciela Kearney1°, Lidia Szczupak1°2°
1° Instituto de Fisiología, Biología Molecular y Neurociencias, UBA-CONICET, Argentina
2° Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
Leeches display a robust motor behavior that allows them to move on solid surfaces through elongation and contraction waves along the longitudinal axis. The neuronal network that controls the crawling behavior can be studied at the level of the isolated nervous system (crawling), where recordings of identified motoneurons show a motor pattern compatible with the behavior. Isolated nerve cords or single ganglia, treated with dopamine (DA), exhibit rhythmic activation of the motoneurons responsible for elongation and contraction with due timing.
To study signal transmission among ganglia we analyzed the motor pattern elicited in three-ganglion chains, isolated from the cord and from the periphery. The three interconnected ganglia show coordinated rhythmic motor activity, indicating that they exchange signals that grant a basic correlated rhythmic activity (Kearney et al, 2022). To further analyze interganglionic signals we used chains of three ganglia that were chemically compartmentalized, where only the anterior ganglion was treated with DA while the rest of the chain was in normal saline. Local application of DA elicited crawling in the treated ganglion and rhythmic activity in untreated ganglia. Activity propagation in contraction and elongation units was distinct, suggesting that the stimulated ganglion sends two parallel intersegmental signals. These signals are not sufficient to generate coordinated crawling in the chain but may contribute to its establishment.