title: Propriospinal neurons with ascending collaterals to the dorsal medulla, the thalamus and the tectum: a retrograde fluorescent double-labeling study of the cervical cord of the rat.
abstract: Branching neurons with descending propriospinal collaterals and ascending collaterals to the dorsal medulla, the thalamus and the tectum were studied in the rat's cervical spinal cord (C1-C8), using the retrograde fluorescent double-labeling technique: Diamidino Yellow Dihydrochloride (DY) was injected in the cord at T2, True Blue (TB) was injected in the brain stem. DY-labeled descending propriospinal neurons were present in all laminae, except lamina IX. They were concentrated in lamina I, laminae IV to VIII, and in the lateral spinal nucleus, LSN. TB-labeled neurons projecting to the dorsal medulla were concentrated in lamina IV and the medial parts of laminae V and VI (probably representing postsynaptic dorsal column--PSDC--neurons), but were also present in lamina I, the LSN, the lateral dorsal horn, and in laminae VII and VIII. DY-TB double-labeled neurons giving rise to both a descending propriospinal collateral and an ascending collateral to the dorsal medulla were intermingled with the TB single-labeled neurons. About 4% of the descending propriospinal neurons gave rise to an ascending collateral to the dorsal column nuclei; these double-labeled cells constitute a sizable fraction (10%) of the PSDC neurons. TB-labeled spinothalamic and spinotectal neurons were located in lamina I, the lateral cervical nucleus (LCN), and LSN, the lateral lamina V, lamina VII and VIII, lamina X and in the spinal extensions of the dorsal column nuclei, predominantly contralateral to the TB injections. DY-TB double-labeled neurons were present throughout C1-C8 in the LSN, lateral lamina V, lamina VIII, ventromedial lamina VII, and lamina X. Only very few were observed in lamina I and the LCN, and none in the spinal extensions of the dorsal column nuclei. The double-labeled neurons constituted only a minor fraction of all labeled neurons; 3-5% of the spinothalamic neurons and about 1-7% of the spinotectal neurons were double-labeled. Conversely, only about 1% of the labeled descending propriospinal neurons gave rise to an ascending spinothalamic collateral, and even fewer (0.1 to 0.6%) to a collateral to the dorsal midbrain. The LSN displayed the highest relative content of branching neurons. Up to 20% of its ascending spinothalamic and spinotectal neurons and up to 8% of its descending propriospinal neurons were found to be branching neurons, indicating that the LSN constitutes an unique cell-group in the rat spinal cord.
authors.affiliation: Department of Anatomy-II, Erasmus University Rotterdam, The Netherlands.
authors.forename: C A
authors.initials: CA
authors.lastname: Verburgh
authors.forename: J
authors.initials: J
authors.lastname: Voogd
authors.forename: H G
authors.initials: HG
authors.lastname: Kuypers
authors.forename: H P
authors.initials: HP
authors.lastname: Stevens
mesh_terms: D000818:Animals; D005456:Fluorescent Dyes; D008526:Medulla Oblongata / Q000166:cytology* / Q000502:physiology; D009434:Neural Pathways / Q000033:anatomy & histology; D009475:Neurons, Afferent / Q000166:cytology* / Q000502:physiology; D011434:Proprioception / Q000502:physiology*; D051381:Rats; D013116:Spinal Cord / Q000502:physiology*; D013477:Superior Colliculi / Q000166:cytology* / Q000502:physiology; D013788:Thalamus / Q000166:cytology* / Q000502:physiology
chemical_list: D005456:Fluorescent Dyes