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Segmental specialization of neuronal connectivity in the leech
G Wittenberg1, C M Loer, S A Adamo
1Department of Biology, University of California, San Diego, La Jolla 92093-0322.
Journal of Comparative Physiology. A, Sensory, Neural, and Behavioral Physiology
|September 1, 1990
Summary
Leech reproductive Retzius cells are physiologically distinct, showing altered electrical coupling and responses to stimuli compared to standard Retzius cells. This difference likely stems from downstream pathway variations, not the P cells themselves.
Area of Science:
- Neuroscience
- Leach Physiology
- Cellular Electrophysiology
Background:
- The leech Hirudo medicinalis possesses two serotonergic Retzius cells per segmental ganglion.
- Retzius cells in reproductive ganglia exhibit morphological differences, suggesting potential physiological distinctions.
Purpose of the Study:
- To investigate the physiological differences between standard and reproductive Retzius cells in the leech Hirudo medicinalis.
- To elucidate the electrophysiological properties and synaptic connections of Retzius cells in different segmental ganglia.
Main Methods:
- Electrophysiological recordings to assess electrical coupling between Retzius cells.
- Stimulation experiments (swim motor pattern initiation, mechanosensory input) to observe Retzius cell responses.
- Pharmacological manipulation (divalent cations) to probe synaptic pathways.
Main Results:
- Reproductive Retzius cells exhibit weaker electrical coupling compared to standard Retzius cells.
- Standard Retzius cells depolarize upon stimulation, while reproductive Retzius cells either hyperpolarize or show no response.
- The mechanosensory-to-Retzius pathway in standard ganglia is polysynaptic, requiring interneuron activation.
Conclusions:
- Physiological differences in electrical coupling and response patterns distinguish reproductive Retzius cells.
- The distinct responses of reproductive Retzius cells are likely due to downstream pathway alterations, potentially involving receptor differences.
- These findings highlight functional specialization of neural circuits in reproductive segments of the leech.