title: Normal development and effects of deafferentation on the morphology of superior collicular neurons projecting to the lateral posterior nucleus in hamster.
abstract: Visually responsive neurons in the superficial layers of the hamster's superior colliculus (SC) can be divided into distinct morphological and functional classes. In the preceding paper (Mooney et al., '91), we showed that neonatal enucleation has only slight and insignificant effects upon the structural characteristics of cells within a given class, but results in a significant reduction of neurons (narrow and widefield vertical cells) with dorsally directed dendritic arbors. In an effort to determine whether this change reflected differential transneuronal degeneration of these cell types or alterations in the dendritic arbors of surviving cells, this study re-examined this issue by restricting the analysis to a specific and relatively homogeneous subpopulation of superficial layer neurons, those that project to the lateral posterior nucleus (LP). Physiological recordings demonstrated that most (64.7%) tecto-LP cells in neonatally enucleated hamsters develop somatosensory receptive fields. The combination of retrograde tracing and injection of cells with Lucifer yellow in a fixed slice preparation demonstrated that nearly 75% of tecto-LP cells in normal adult hamsters are widefield vertical cells while less than 25% of the neurons filled in neonatally enucleated adults are in this class. Most of the tecto-LP cells in the neonatally enucleated adult hamsters were either horizontal cells (19.5%), giant stellate cells (24.6%), or had dendrites that were directed only toward the deep SC laminae (10.3%). Differential enucleation-induced cell death could not account for all of these changes. Tecto-LP neurons were retrogradely labelled with the carbocyanine dye, Di-I, in hamsters on postnatal day (P-) 0 (the day of birth) through P-10. As early as P-0, most retrogradely labelled neurons could be identified as either widefield (44.6%) or narrowfield (18.9%) vertical cells. These results, when considered together with those from the normal adult and neonatally enucleated adult hamsters, support the conclusion that neonatal eye removal results in a reorganizaton of the dendritic arbors of some collicular neurons that have already undergone considerable development at the time of the lesion.
authors.affiliation: Department of Anatomy, Medical College of Ohio, Toledo 43699.
authors.forename: R D
authors.initials: RD
authors.lastname: Mooney
authors.forename: S V
authors.initials: SV
authors.lastname: Savage
authors.forename: S
authors.initials: S
authors.lastname: Hobler
authors.forename: T D
authors.initials: TD
authors.lastname: King
authors.forename: R W
authors.initials: RW
authors.lastname: Rhoades
mesh_terms: D000344:Afferent Pathways / Q000166:cytology / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D002232:Carbocyanines; D006224:Cricetinae; D004558:Electric Stimulation; D015353:Eye Enucleation; D005452:Fluoresceins; D005829:Geniculate Bodies / Q000166:cytology / Q000502:physiology; D066298:In Vitro Techniques; D007546:Isoquinolines; D008863:Microspheres; D009475:Neurons, Afferent / Q000502:physiology*; D010316:Particle Size; D010477:Perfusion; D010812:Physical Stimulation; D013477:Superior Colliculi / Q000166:cytology / Q000254:growth & development / Q000502:physiology*
chemical_list: D002232:Carbocyanines; D005452:Fluoresceins; D007546:Isoquinolines; C024286:3,3'-dioctadecylindocarbocyanine; C017475:lucifer yellow