title: Effects of neonatal and adult enucleation on the synaptic organization of the serotoninergic projection to the superficial gray layer of the hamster's superior colliculus.
abstract: Previous experiments from this laboratory have demonstrated that either neonatal or adult enucleation results in a marked increase in the density of the serotoninergic (5-HT) projection to the superficial layers of the hamster's superior colliculus (SC). The present study was undertaken to determine whether this alteration in the density of the 5-HT projections to SC in hamsters that sustained eye removals was associated with any change in the synaptic organization of this pathway. In normal adult hamsters, only 4.0% of 500 5-HT-immunoreactive profiles made synaptic contacts in the stratum griseum superficiale (SGS). Of these, 65% were axoaxonic, 30% were axodendritic, and 5% were axosomatic. In contrast, 22% of 400 5-HT-positive profiles in the neonatally enucleated hamsters and 17.5% of 400 such profiles in hamsters that sustained eye removals in adulthood made synaptic contacts. In the neonatal enucleates, 66% of the contacts were axoaxonic, 33% were axodendritic, and 1% were axosomatic. In the adult enucleates, 73% of the contacts were axoaxonic, 26% were axodendritic, and 1% were axosomatic. Thus, both neonatal and adult enucleation increase the percentage of 5-HT-positive profiles that make synaptic contacts in SC, but neither manipulation significantly changes the distribution of these contacts among different types of postsynaptic targets.
authors.affiliation: Dept. of Anatomy and Neurobiology, Medical College of Ohio, Toledo 43699-0008, USA.
authors.forename: E A
authors.initials: EA
authors.lastname: Arce
authors.forename: R W
authors.initials: RW
authors.lastname: Rhoades
authors.forename: R D
authors.initials: RD
authors.lastname: Mooney
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000737:chemistry / Q000648:ultrastructure*; D006224:Cricetinae; D003712:Dendrites / Q000737:chemistry / Q000648:ultrastructure*; D015353:Eye Enucleation; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D009434:Neural Pathways / Q000737:chemistry / Q000648:ultrastructure; D012701:Serotonin / Q000032:analysis*; D013477:Superior Colliculi / Q000737:chemistry / Q000254:growth & development / Q000648:ultrastructure*; D013569:Synapses / Q000737:chemistry / Q000648:ultrastructure*
chemical_list: D012701:Serotonin