Biomedical subjects

J Cang

Publications and source records attributed to J Cang.

3 recordsLinked to original sources

PubMed2001

Sensory modification of leech swimming: interactions between ventral stretch receptors and swim-related neurons.

The neuronal circuits that generate the leech swimming rhythm comprise oscillatory interneurons that provide appropriately phased output to drive swim-related motoneurons. Within ganglia, these interneurons express three phases; between ganglia there exists a phase delay between homologs. Our earlier experiments revealed that stretch receptors embedded in the body wall participate in intersegmental coordination and setting intersegmental phases. To identify the basis for these sensory effects, we mapped interactions between a ventral stretch receptor and swim-related neurons. Connections between this receptor and motoneurons are weak and variable in quiescent preparations, but during fictive swimming stretch receptor activation modulates motoneuron oscillations, hence, these effects are polysynaptic, mediated by interneurons. We identified a strong, nonrectifying, and apparently direct electrical connection between the stretch receptor and oscillator neuron 33. The ventral stretch receptor also interacts with most of the other oscillatory interneurons, including inhibitory inputs to cells 28 and 208, excitatory input to the contralateral cell 115, and mixed input to the ipsilateral cell 115. These direct and indirect interactions can account for previously described effects of body-wall stretch on motoneuron activity. They also could mediate the previously described modification of intersegmental phase relationships by appropriately phased stretch receptor activation.

Animals↗

PubMed2001

Sensory and central mechanisms control intersegmental coordination.

Recent experiments on the sensory and central mechanisms that coordinate animal locomotory movements have advanced our understanding of the relative importance of these two components and overturned some previously held notions. In different experimental preparations, sensory inputs and central pattern generators have now been shown to play different roles in setting intersegmental phase lags.

Animals↗

PubMed2000

Sensory modification of leech swimming: rhythmic activity of ventral stretch receptors can change intersegmental phase relationships.

For segmented animals to generate optimal locomotory movements, appropriate phase relationships between segmental oscillators are crucial. Using swimming leeches, we have investigated the role of sensory input in establishing such relationships. We found that the stretch receptors associated with ventral longitudinal muscles encode the information of muscle contraction during swimming via membrane potential oscillations, with amplitudes of up to 10 mV at our recording site. We subsequently modified the activity of ventral stretch receptors (VSRs) by injecting rhythmic current at different phases of the swim cycle and determined intersegmental phase lags by comparing the delay between the discharges of serially homologous motoneurons in three adjacent segments of isolated nerve cords. When no current was injected, the phase lag between neighboring segments was 8.6 +/- 0.8 degrees (mean +/- SEM; n = 20), with large phase variations from cycle to cycle, between different episodes, and between different preparations. When the phase of stretch receptor activity was set to 90-150 degrees by current injection, the phase of the motoneuron activity in the ganglion was consistently retarded by approximately 5 degrees. It was advanced by approximately 5 degrees when the VSR phase was set to 240-300 degrees. Therefore, the rhythmic activity of the ventral stretch receptor generated during swimming can change intersegmental phase lags of leech ganglia in a phase-dependent manner. These stretch receptors may set the optimal intersegmental phases during swimming movement in intact leeches.

Animals↗