The neuronal system of the saccus vasculosus of trout (Salmo trutta fario and Oncorhynchus mykiss): an immunocytochemical and nerve tracing study.
The neuronal system of the saccus vasculosus of two species of trout was studied with immunocytochemical methods and carboindocyanine-dye (DiI) tract-tracing. The cerebrospinal-fluid-contacting neurons of the saccus were immunoreactive for gamma-aminobutyric acid (GABA), glutamic acid decarboxylase (GAD), and neuropeptide Y (NPY). Immunostaining of alternate sections of the saccus vasculosus of fry with anti-GAD and anti-NPY indicated that these substances were colocalized. The tractus sacci vasculosi and the neuropil of the nucleus sacci vasculosi were also immunoreactive to these substances. The GABA, GAD, and neuropeptide Y immunoreactivity of the saccus vasculosus system appeared early in trout ontogeny. After applying DiI to various levels of the tractus sacci vasculosi of adult trout, we observed massive bilateral saccular projections to the nucleus sacci vasculosi and could follow the course of the sacco-thalamic tract. This tract extended in the subependymal region of the thalamus rostral to the nucleus sacci vasculosi and split into two small tracts that reached the subhabenular-preoptic region. Sacco-thalamic fibers formed extensive periependymal plexuses along their trajectory. Interestingly, no clear evidence of the existence of a saccopetal system was obtained. On the basis of these results, we postulate that the saccus vasculosus system modulates the function of centers of the posterior tubercle and periventricular thalamus.
Yáñez
J
J
Departamento de Biología Celular y Molecular, Facultad de Ciencias, Universidad de La Coruña, E-15071 La Coruña, Spain. bfandadon@ucs.es
Rodríguez
M
M
Pérez
S
S
Adrio
F
F
Rodríguez-Moldes
I
I
Manso
M J
MJ
Anadón
R
R
D000375:Aging; D000818:Animals; D001370:Axonal Transport; D001921:Brain / Q000166:cytology / Q000196:embryology / Q000254:growth & development; D002232:Carbocyanines; D002555:Cerebrospinal Fluid; D004625:Embryo, Nonmammalian; D005456:Fluorescent Dyes; D005968:Glutamate Decarboxylase / Q000032:analysis; D007031:Hypothalamus / Q000166:cytology* / Q000196:embryology / Q000254:growth & development; D009474:Neurons / Q000166:cytology*; D009478:Neuropeptide Y / Q000032:analysis; D017686:Oncorhynchus mykiss / Q000033:anatomy & histology*; D014337:Trout / Q000033:anatomy & histology*; D005680:gamma-Aminobutyric Acid / Q000032:analysis
C035005:3,3'-dihexadecylindocarbocyanine; D002232:Carbocyanines; D005456:Fluorescent Dyes; D009478:Neuropeptide Y; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase