Heterogeneous expression of γ-aminobutyric acid and γ-aminobutyric acid-associated receptors and transporters in the rat suprachiasmatic nucleus

Michael A. Belenky, Yosef Yarom, Gary E. Pickard

Research output: Contribution to journalArticlepeer-review

85 Scopus citations


The hypothalamic suprachiasmatic nucleus (SCN) is the primary mammalian circadian clock that regulates rhythmic physiology and behavior. The SCN is composed of a diverse set of neurons arranged in a tight intrinsic network. In the rat, vasoactive intestinal peptide (VIP)- and gastrin-releasing peptide (GRP)-containing neurons are the dominant cell phenotypes of the ventral SCN, and these cells receive photic information from the retina and the intergeniculate leaflet. Neurons expressing vasopressin (VP) are concentrated in the dorsal and medial aspects of the SCN. Although the VIP/GRP and VP cell groups are concentrated in different regions of the SCN, the separation of these cell groups is not absolute. The inhibitory neurotransmitter γ-aminobutyric acid (GABA) is expressed in most SCN neurons irrespective of their location or peptidergic phenotype. In the present study, immunoperoxidase labeling, immunofluorescence confocal microscopy, and ultrastructural immunocytochemistry were used to examine the spatial distribution of several markers associated with SCN GABAergic neurons. Glutamate decarboxylase, a marker of GABA synthesis, and vesicular GABA transporter were more prominently observed in the ventral SCN. KCC2, a K+/Cl - cotransporter, was highly expressed in the ventral SCN in association with VIP- and GRP-producing neurons, whereas VP neurons in the dorsal SCN were devoid of KCC2. On the other hand, GABAB receptors were observed predominantly in VPergic neurons dorsally, whereas, in the ventral SCN, GABAB receptors were associated almost exclusively with retinal afferent fibers and terminals. The differential expression of GABAergic markers within the SCN suggests that GABA may play dissimilar roles in different SCN neuronal phenotypes.

Original languageEnglish
Pages (from-to)708-732
Number of pages25
JournalJournal of Comparative Neurology
Issue number4
StatePublished - 1 Feb 2008
Externally publishedYes


FundersFunder number
National Eye InstituteR01EY017809
National Institute of Neurological Disorders and StrokeR01NS035615


    • Circadian clock
    • GABA
    • GABA receptors and transporters
    • Immunocytochemistry
    • KCC2
    • Suprachiasmatic nucleus


    Dive into the research topics of 'Heterogeneous expression of γ-aminobutyric acid and γ-aminobutyric acid-associated receptors and transporters in the rat suprachiasmatic nucleus'. Together they form a unique fingerprint.

    Cite this