Expression and plasticity of glutamate receptors in the supraoptic nucleus of the hypothalamus

Abstract

Magnocellular neuroendocrine cells (MNCs) of the supraoptic nucleus of the hypothalamus (SON) produce and release the hormones vasopressin (VP) and oxytocin (OT) in response to a variety of stimuli to regulate body water and salt, parturition and lactation. Hormone release is influenced by the pattern of neuronal firing of these MNCs, which, in turn, is governed by intrinsic conductances and synaptic inputs, including those mediated by the neurotransmitter glutamate. Functional and molecular evidence has confirmed the expression of AMPA-, NMDA-, and metabotropic-type glutamate receptors in the SON, that together may orchestrate the effects of glutamatergic transmission on neuroendocrine function. However, the specific roles of the different subtypes of glutamate receptors is not yet clear. As with other central neurons, the subunit composition of glutamate receptors on MNCs will likely determine their properties and may potentially help define the differential properties of VP- and OT-producing MNCs. Possible functions of glutamate receptors on SON MNCs include altering excitatory synaptic transmission of osmotic information, neuronal firing, hormone production and release, and calcium signaling. Of interest are the anatomical, molecular, and functional changes at glutamatergic synapses in the SON that occur in response to pertinent physiological stimuli or development. These types of plasticity may include changes in glutamatergic synaptic density, glutamate receptor levels, or glutamate receptor subunit expression, all of which can affect the efficiency of synaptic transmission.

Non‐N‐methyl‐D‐aspartate glutamate receptors in the paraventricular nucleus of hypothalamus mediate the pressor response evoked by noradrenaline microinjected into the lateral septal area in rats

“…Glutamatergic receptors are divided into ionotropic and metabotropic receptor subfamilies. Ionotropic receptors act as glutamate‐gated cation channels, whereas metabotropic receptors modulate the production of second messengers via G proteins and affect other ion channels as well as intracellular processes (Pak and Curras‐Collazo, 2002). The ionotropic receptors are classified into two types according to agonist selectivity and amino acid homology: N‐methyl‐D‐aspartate (NMDA) receptors and non‐NMDA receptors, which are subdivided into amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate (AMPA) and kainate (KA) subtypes (Hollmann and Heinemann, 1994).…”

Relationships of circulating pregnanolone isomers and their polar conjugates to the status of sex, menstrual cycle, and pregnancy

“…The 5a-and 5b-PIC are effective as positive and negative modulators of N-methyl-D-aspartate receptors (NMDA-R) respectively (Park-Chung et al 1997, Weaver et al 2000. The activation of NMDA-R in hypothalamic magnocellular neuroendocrine cells of the supraoptic nucleus may induce oxytocin production (Pak & Curras-Collazo 2002), resulting in onset of parturition.…”

Role of N‐methyl‐D‐aspartate and non‐N‐methyl‐D‐aspartate receptors in the cardiovascular effects of L‐glutamate microinjection into the hypothalamic paraventricular nucleus of unanesthetized rats

“…The non‐NMDA receptors are further divided into α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionate (AMPA) and kainate (KA) receptor subtypes (Hollmann and Heinemann,1994). Metabotropic glutamate receptors (mGLURs) are coupled to G‐protein and activate second messengers and can affect other ion channels as well as intracellular processes (Pak and Curras‐Collazo,2002). Immunohistochemical and pharmacological studies have shown that the hypothalamus, among areas involved in cardiovascular control, contains high levels of glutamate and ionotropic glutamatergic receptors (Meeker et al,1994; Singewald and Philippu,1996).…”