Chapter 10 Postsynaptic GABAB receptors in supraoptic oxytocin and vasopressin neurons

Abstract

Publisher Summary This chapter describes the expression and function of postsynaptic gamma-aminobutyric acid (GABA B ) receptors in magnocellular neurons, using a combination of in vitro patch-clamp recordings and immunohistochemical approaches. GABA B receptor is an unusual G-protein-coupled receptor, composed of two seven transmembrane domain subunits, GABA B R1 and GABA B R2, respectively. Heteromerization of these subunits results in a functional receptor at the cell surface. Immunohistochemical techniques were used to study the expression of GABA B receptor subunits in identified oxtytocin (OT) and vasopressin (VP) neurons. Triple fluorescent immunohistochemical experiments were performed in 30 μm coronal hypothalamic brain slices obtained from Sprague–Dawley male and female rats. Antibodies raised against GABA B R1 and/or GABA B R2 receptor subunits were combined simultaneously with antibodies raised against OT and VP neurophysins. Colocalization of the three antibodies in individual supraoptic (SON) and paraventrieular nuclei (PVN) neurons was assessed. GABAB receptor subunit immunoreactivity was quantified using an optical density analysis. The electrical activity of SON neurons was recorded using the perforated patch-clamp configuration, which allows electrical access to the cell, preventing the dialysis of the intracellular environment. GABA B receptor immunoreactivity was significantly stronger in VP, as compared to OT neurons, suggesting that the expression of this receptor in the magnocellular neuroendocrine system is cell-type dependent.