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Afferent projection from the dorsal nucleus of the raphe to the flocculus in cats
Insights
Horseradish peroxidase (HRP) injections into the cat cerebellar flocculus revealed labeled neurons in the dorsal raphe nucleus. Stimulation of this nucleus elicited responses in the flocculus, indicating a neural pathway.
Area of Science:
- Neuroscience
- Cerebellar research
- Brainstem pathways
Background:
- The cerebellar flocculus plays a role in motor control and eye movement.
- The dorsal raphe nucleus is a major source of serotonin in the brain.
Purpose of the Study:
- To investigate the neural connections between the cerebellar flocculus and the dorsal raphe nucleus in cats.
- To identify the origin of cerebellar inputs to the dorsal raphe nucleus.
Main Methods:
- Horseradish peroxidase (HRP) was iontophoretically injected into the cerebellar flocculus of cats.
- Neurons retrogradely labeled with HRP were identified in the brainstem.
- Electrical stimulation was used to evoke responses in the flocculus.
Main Results:
- Neurons in the caudal dorsal nucleus of the raphe were labeled with HRP after injection into the flocculus.
- Electrical stimulation of the dorsal raphe nucleus elicited orthodromic evoked potentials in the flocculus.
- Low threshold stimulation sites were localized to a small area within the dorsal nucleus of the raphe.
Conclusions:
- The dorsal raphe nucleus projects to the cerebellar flocculus in cats.
- This study identifies a direct neural pathway between the dorsal raphe nucleus and the cerebellar flocculus.
Abstract:
Horseradish peroxidase (HRP) was injected iontophoretically into the cerebellar flocculus in cats. The neurons labeled with HRP were recognized in the caudal part of the dorsal nucleus of the raphe. Electrical stimulation of this region elicited orthodromic evoked potentials in the flocculus and stimulated sites of low threshold current necessary to evoke the responses were limited in a small area corresponding well with the dorsal nucleus of the raphe.