GABA, GABA transporters, GABAAreceptor subunits, and GAD mRNAs in the rat parabrachial and K�lliker-Fuse nuclei

Abstract

In the present study, we investigated the key molecules that determine gamma-aminobutyric acid (GABA)ergic signal transduction in the parabrachial/Kölliker-Fuse complex (PB/KF) by means of immunocytochemistry and in situ hybridization. Our data demonstrate a dense plexus of GABA-immunoreactive (-ir) varicosities throughout the nuclei of the PB and the KF. The number of neurons expressing GAD65 or GAD67 mRNA was fairly low in the PB, whereas caudally in the KF an accumulation of GAD-expressing neurons was observed. The GABA transporter-3 (GAT-3) was detected in all parts of the PB/KF, whereas immunolabeling for GAT1 was not observed. All nuclei of the PB and the KF exhibited immunoreactivity for the gamma2-, alpha2-, and alpha3-subunits of the GABA(A) receptor. Gamma2-ir was strong and similar in all PB/KF nuclei. In contrast, alpha2-labeling was particularly intense in the superior lateral PB, and alpha3-labeling was most prominent in the external lateral and external medial PB, compared with the remaining nuclei. With respect to the subcellular localization, we found gamma2-ir in cell bodies and higher order dendrites, whereas alpha2- and alpha3-ir was predominantly found in cell bodies. Immunolabeling for the beta2/3- and the alpha1-subunit was seen in cell bodies and presumed dendritic profiles. The staining intensity was strongest in the dorsal lateral PB. Most importantly, the external lateral PB and the waist area were totally devoid of beta2/3- and alpha1-ir. Our data suggest that neural processing in the PB/KF is under a strong GABAergic inhibition that is apparently mediated by different types of GABA(A) receptors in functionally different pathways through the PB/KF.

Morphological and physiological evidence of a synaptic connection between the lateral parabrachial nucleus and neurons in the A7 catecholamine cell group in rats

“…Moreover, the effect of DAMGO on EPSC amplitude was associated with an increase in PPR, showing that μ-opioid receptors are located at the axonal terminal of LPB neurons and regulate glutamate release. The EPSCs evoked by local LPB stimulation were blocked by application of non-NMDA and NMDA receptor blockers; these results echo previous studies arguing that the majority of parabrachial neurons are glutamatergic [ 31 , 32 ]. The features of short delay-latency, rapid and smooth rise phase, of PLB-A7 EPSCs suggest that PLB-A7 EPSCs are monosynaptic.…”

Pontine Mechanisms of Respiratory Control

“…The noradrenergic A7 cell group also overlaps with the KF. In addition to GABA, glycine, and noradrenalin receptors, various glutamate (AMPA/kainic acid, NMDA, and metabotropic receptors (59, 149–152) and cholinergic and serotonergic (5-HT) receptors are expressed in the PB and KF nuclei (103, 165, 244). Moreover, large subset of neuropeptide transmitters such as neurotensin, cholecystokinin, substance P, somatostatin, and calcitonin gene-related peptide and their associated receptors are also expressed (324–327).…”

Methodological Limitations in Determining Astrocytic Gene Expression

“…In rat thalamus GAT1 and GAT3 proteins are mainly expressed in astrocytes and the stain of GAT3 is more intense than that of GAT1 ( 28 ). In the parabrachial and Kölliker-Fuse nuclei GAT3 was detected, whereas GAT1 was absent ( 29 ). Cerebellar mRNA and protein staining of GAT2 and GAT3 was also primarily glial, with GAT2 stain in the granule layer and GAT3 stain in the deep nuclei ( 24 , 27 ).…”