title: Pretectal connections in turtles with special reference to the visual thalamic centers: a hodological and gamma-aminobutyric acid-immunohistochemical study.
abstract: Projections of the pretectal region to forebrain and midbrain structures were examined in two species of turtles (Testudo horsfieldi and Emys orbicularis) by axonal tracing and immunocytochemical methods. Two ascending gamma-aminobutyric acid (GABA)ergic pathways to thalamic visual centers were revealed: a weak projection from the retinorecipient nucleus lentiformis mesencephali to the ipsilateral nucleus geniculatus lateralis pars dorsalis and a considerably stronger projection from the nonretinorecipient nucleus pretectalis ventralis to the nucleus rotundus. The latter is primarily ipsilateral, with a weak contralateral component. The interstitial nucleus of the tectothalamic tract is also involved in reciprocal projections of the pretectum and nucleus rotundus. In addition, the pretectal nuclei project reciprocally to the optic tectum and possibly to the telencephalic isocortical homologues. Comparison of these findings with previous work on other species reveals striking similarities between the pretectorotundal pathway in turtles and birds and in the pretectogeniculate pathway in turtles, birds, and mammals.
authors.affiliation: Laboratory of Evolution of Neuronal Interactions, Sechenov Institute, Academy of Sciences, 194223 St. Petersburg, Russia.
authors.forename: N B
authors.initials: NB
authors.lastname: Kenigfest
authors.forename: M G
authors.initials: MG
authors.lastname: Belekhova
authors.forename: J
authors.initials: J
authors.lastname: Repérant
authors.forename: J P
authors.initials: JP
authors.lastname: Rio
authors.forename: N P
authors.initials: NP
authors.lastname: Vesselkin
authors.forename: R
authors.initials: R
authors.lastname: Ward
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism / Q000648:ultrastructure; D001710:Biotin / Q000031:analogs & derivatives; D003911:Dextrans; D005456:Fluorescent Dyes; D006735:Horseradish Peroxidase; D007267:Injections / Q000379:methods; D013477:Superior Colliculi / Q000166:cytology* / Q000378:metabolism; D013788:Thalamus / Q000166:cytology* / Q000378:metabolism; D014426:Turtles / Q000033:anatomy & histology* / Q000502:physiology; D014795:Visual Pathways / Q000166:cytology* / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D003911:Dextrans; D005456:Fluorescent Dyes; C076397:biotinylated dextran amine; D005680:gamma-Aminobutyric Acid; D001710:Biotin; D006735:Horseradish Peroxidase