title: Characterization of gabaergic neurons within the human medial mamillary nucleus.
abstract: The morphology, distribution and relative frequency of GABAergic neurons in the medial mamillary nucleus (MMN) of normal human individuals was studied using a glutamic acid decarboxylase (GAD) antiserum. GAD-immunoreactive (GAD-IR) neurons were found sparsely distributed throughout the MMN and most displayed a simple bipolar morphology. A small population of large diameter GAD-IR neurons was found in the white matter capsule adjacent to the ventral border of the MMN. Results of double-labeling experiments revealed no evidence of calretinin, parvalbumin or calbindin immunoreactivities co-localizing with GAD-IR neurons. GAD-IR neurons of the MMN had an average somal area of 138+/-41 microm2, compared with the average somal area of 384+/-137 microm2 for the population of MMN neurons as a whole. GAD-IR neurons had a tendency to cluster in groups of two (and occasionally three) and showed a distribution gradient across the MMN with higher densities being found near the insertion of the fornix, the origin of the mamillo-thalamic tract and toward the medial MMN border. Quantitative estimates of GAD-IR neuron frequency revealed the GAD-IR phenotype to constitute an average of 1.7% percent of the total neuron population within the human MMN. These findings suggest that inhibitory activity within the human MMN is regulated in part by a small population of intrinsic GABAergic interneurons.
authors.affiliation: Department of Pathology, The University of Sydney, Sydney, NSW 2006, Australia. gavind@med.usyd.edu.au
authors.forename: G
authors.initials: G
authors.lastname: Dixon
authors.forename: T
authors.initials: T
authors.lastname: Garrick
authors.forename: I
authors.initials: I
authors.lastname: Whiteman
authors.forename: M
authors.initials: M
authors.lastname: Sarris
authors.forename: S
authors.initials: S
authors.lastname: Sithamparanathan
authors.forename: C G
authors.initials: CG
authors.lastname: Harper
mesh_terms: D000328:Adult; D002135:Calcium-Binding Proteins / Q000378:metabolism; D016764:Cell Polarity / Q000502:physiology; D048429:Cell Size / Q000502:physiology; D003712:Dendrites / Q000201:enzymology / Q000648:ultrastructure; D005260:Female; D020712:Fornix, Brain / Q000502:physiology; D005968:Glutamate Decarboxylase / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008326:Mammillary Bodies / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D008875:Middle Aged; D009433:Neural Inhibition / Q000502:physiology*; D009434:Neural Pathways / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D010641:Phenotype; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D002135:Calcium-Binding Proteins; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase