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γ-Aminobutyric acid (GABA), the major inhibitory neurotransmitter in the brain, acts via two different type of GABA receptors. GABAA receptors are composed of five subunits that belong to eight different classes. Depending on their subunit composition, distinct pharmacological and electrophysiological properties are obtained. GABA is produced in certain hypothalamic neurones known to be involved in control of feeding behaviour. We report the detailed immunohistochemical localization of four GABAAR α subunits in hypothalamic regions associated with the regulation of feeding behaviour. Immunoreactive structures for all studied GABAAR α subunits were observed in the hypothalamus, but with subunit-specific staining patterns. GABAAR α1 immunoreactivity was most prominent in the dorsomedial hypothalamic nucleus and in the lateral hypothalamic area (LHA), whereas GABAAR α2, α3 and α5 subunits exhibited particularly strong immunoreactivity in the ventromedial hypothalamic nucleus. In comparison, GABAAR α subunit immunoreactivities were generally weak in the arcuate nucleus. In the ventromedial part of the arcuate nucleus, neuropeptide Y- and agouti-related peptide-containing cell bodies, which also are known to be GABAergic, were immunoreactive for only the GABAAR α3 subunit, whereas pro-opiomelanocortin- and cocaine- and amphetamine-regulated transcript- containing cell bodies located in the ventrolateral subdivision of the arcuate nucleus, showed GABAAR α1, α2 and α3 subunit immunoreactivity. In the LHA, GABAAR α3 subunit immunoreactivity was demonstrated in both melanin-concentrating hormone (MCH) and orexin-containing neurones. In addition, MCH neurones contained GABAAR α2 immunoreactivity. In neurones of the tuberomammillary nucleus, GABAAR α2 and α5 subunits were colocalized with histidine decarboxylase, a marker for histamine-containing neurones. [ABSTRACT FROM AUTHOR]

Abstract γ-aminobutyric acid (GABA) interacts with hypothalamic neuronal pathways regulating feeding behaviour. GABA has been reported to stimulate feeding via both ionotropic GABAA and metabotropic GABAB receptors. The functional form of the GABAB receptor is a heterodimer consisting of GABAB receptor-1 (GABAB R1) and GABAB receptor-2 (GABAB R2) proteins. Within the heterodimer, the GABA-binding site is localized to GABAB R1. In the present study, we used an antiserum to the GABAB R1 protein in order to investigate the cellular localization of GABAB R1-immunoreactive neurones in discrete hypothalamic regions implicated in the control of body weight. The colocalization of GABAB R1 immunoreactivity with different chemical messengers that regulate food intake was analysed. GABAB R1-immunoreactive cell bodies were found in the periventricular, paraventricular (PVN), supraoptic, arcuate, ventromedial hypothalamic, dorsomedial hypothalamic, tuberomammillary nuclei and lateral hypothalamic area (LHA). Direct double-labelling showed that glutamic acid decarboxylase (GAD)-positive terminals were in close contact with GABAB R1-containing cell bodies located in all these regions. In the ventromedial part of the arcuate nucleus, GABAB R1-immunoreactive cell bodies were found to contain neuropeptide Y, agouti-related peptide (AGRP) and GAD. In the ventrolateral part of the arcuate nucleus, GABAB R1-immunoreactive cell bodies were shown to contain pro-opiomelanocortin and cocaine- and amphetamine-regulated transcript. In the LHA, GABAB R1 immunoreactivity was present in both melanin-concentrating hormone- and orexin-containing cell populations. In the tuberomammillary nucleus, GABAB R1-immunoreactive cell bodies expressed histidine decarboxylase, a marker for histamine-containing... [ABSTRACT FROM AUTHOR]

gamma-Aminobutyric acid (GABA), the major inhibitory neurotransmitter in the brain, acts via two different type of GABA receptors. GABA(A) receptors are composed of five subunits that belong to eight different classes. Depending on their subunit composition, distinct pharmacological and electrophysiological properties are obtained. GABA is produced in certain hypothalamic neurones known to be involved in control of feeding behaviour. We report the detailed immunohistochemical localization of four GABA(A)R alpha subunits in hypothalamic regions associated with the regulation of feeding behaviour. Immunoreactive structures for all studied GABA(A)R alpha subunits were observed in the hypothalamus, but with subunit-specific staining patterns. GABA(A)R alpha(1) immunoreactivity was most prominent in the dorsomedial hypothalamic nucleus and in the lateral hypothalamic area (LHA), whereas GABA(A)R alpha(2), alpha(3) and alpha(5) subunits exhibited particularly strong immunoreactivity in the ventromedial hypothalamic nucleus. In comparison, GABA(A)R alpha subunit immunoreactivities were generally weak in the arcuate nucleus. In the ventromedial part of the arcuate nucleus, neuropeptide Y- and agouti-related peptide-containing cell bodies, which also are known to be GABAergic, were immunoreactive for only the GABA(A)R alpha(3) subunit, whereas pro-opiomelanocortin- and cocaine- and amphetamine-regulated transcript- containing cell bodies located in the ventrolateral subdivision of the arcuate nucleus, showed GABA(A)R alpha(1), alpha(2) and alpha(3) subunit immunoreactivity. In the LHA, GABA(A)R alpha(3) subunit immunoreactivity was demonstrated in both melanin-concentrating hormone (MCH) and orexin-containing neurones. In addition, MCH neurones contained GABA(A)R alpha(2) immunoreactivity. In neurones of the tuberomammillary nucleus, GABA(A)R alpha(2) and alpha(5) subunits were colocalized with histidine decarboxylase, a marker for histamine-containing neurones.