GABAergic and catecholaminergic synaptic interactions in the macaque hypothalamus: double label immunostaining with peroxidase-antiperoxidase and colloidal gold.
Immunogold staining (IGS) for glutamic acid decarboxylase (GAD) was combined with the peroxidase-antiperoxidase (PAP) technique for tyrosine hydroxylase (TH) to analyze gamma-aminobutyric acid-catecholaminergic neuronal interactions in the rhesus hypothalamus. At the light-microscopic level, TH-immunoreactive (-IR) perikarya and their fibers (brown) were observed in the anterior ventral periventricular area (AVPV), the arcuate nucleus (ARC) and the adjacent periventricular zone (ARC-PVZ). GAD-IR processes (light red) were also present throughout the hypothalamus and appeared to contact some TH-IR neurons. At the electron-microscopic level, PAP was present in perikarya, dendrites, axons and axon terminals of TH-IR neurons. Colloidal gold particles (15 nm) were found only in dendrites and axon terminals of GAD-IR neurons. Labeled GAD terminals typically contained small, clear synaptic vesicles, while TH terminals contained these and sometimes one or two dense-core vesicles. In the ARC and ARC-PVZ, asymmetrical (Gray I) axodendritic synapses occurred between GAD and TH-IR profiles, with TH/GAD directionality more prevalent. Symmetrical (Gray II) synapses were less common, with either TH or GAD presynaptic in axodendritic and dendrodendritic contacts. GAD/GAD interactions were not observed, but TH/TH contacts appeared to be mostly dendrodendritic. In the AVPV, only symmetrical synapses were encountered, and their directionality was difficult to determine. GAD- and TH-IR dendrites frequently established dendrodendritic synapses, but GAD/TH dendrosomatic synapses were seldom seen. These results illustrate the complex interactions of GAD- and TH-containing elements in the neuroendocrine hypothalamus.
D000818:Animals; D004298:Dopamine / Q000502:physiology*; D005260:Female; D005968:Glutamate Decarboxylase / Q000378:metabolism; D007031:Hypothalamus / Q000201:enzymology / Q000502:physiology* / Q000648:ultrastructure; D007124:Immunoenzyme Techniques; D008253:Macaca mulatta; D008854:Microscopy, Electron; D009435:Synaptic Transmission; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D005680:gamma-Aminobutyric Acid; D014446:Tyrosine 3-Monooxygenase; D005968:Glutamate Decarboxylase; D004298:Dopamine