Glutamate, the Dominant Excitatory Transmitter in Neuroendocrine Regulation

Abstract

Glutamate has been found to play an unexpectedly important role in neuroendocrine regulation in the hypothalamus, as revealed in converging experiments with ultrastructural immunocytochemistry, optical physiology with a calcium-sensitive dye, and intracellular electrical recording. There were large amounts of glutamate in boutons making synaptic contact with neuroendocrine neurons in the arcuate, paraventricular, and supraoptic nuclei. Almost all medial hypothalamic neurons responded to glutamate and to the glutamate agonists quisqualate and kainate with a consistent increase in intracellular calcium. In all magnocellular and parvocellular neurons of the paraventricular and arcuate nuclei tested, the non-NMDA (non-N-methyl-D-aspartate) glutamate antagonist CNQX (cyano-2,3-dihydroxy-7-nitroquinoxaline) reduced electrically stimulated and spontaneous excitatory postsynaptic potentials, suggesting that the endogenous neurotransmitter is an excitatory amino acid acting primarily on non-NMDA receptors. These results indicate that glutamate plays a major, widespread role in the control of neuroendocrine neurons.

Oxytocin as a natural antipsychotic: a study using oxytocin knockout mice

“…Most research to date examining interactions between the Oxt and glutamatergic systems has focused on the hypothalamic magnocellular Oxt neurons where glutamatergic circuits synchronize the bursting activity of magnocellular Oxt neurons in organotypic cultures 62 and glutamate is responsible for the fast excitatory input into the magnocellular neurons. [63][64][65][66] Dendritic release of Oxt can reduce glutamatergic excitatory synaptic transmission through presynaptic actions in these nuclei. 67 Also, in acutely dissected rat SON preparations, combined vasopressin and Oxt application inhibits glutamate release.…”

Metabotropic Glutamate Receptor Subtype 7 Ablation Causes Dysregulation of the HPA Axis and Increases Hippocampal BDNF Protein Levels: Implications for Stress-Related Psychiatric Disorders

“…Glutamatergic neurotransmission has long been implicated as a critical regulator of the stress response (van den Pol et al, 1990;Brann, 1995). mGluRs in particular appear to play a crucial role in mediating neuroendocrine responses.…”

Symposium Proceedings

“…In the ventromedial hypothalamic nucleus, a co-localization of cx3 and /1 mRNAs was found, while the dorsal medial hypothalamus was labelled by xl and a3 probes as assessed by in situ hybridization (Malosio et al 1991 (Moss et al 1972) and rats (Bioulac et al 1978;. More recent experiments have demonstrated that glutamate is present within axon terminals forming asymmetric synapses onto MNCs in the supraoptic nucleus of the rat (Meeker et al 1989;van den Pol et al 1990 Gribkoff, 1991;Yang et al 1994). While such findings imply that receptors for glutamate must be expressed in the soma-dendritic membrane of MNCs, these cells are also known to be morphologically and physiologically resistant to the neurodegenerative effects of glutamatergic excitotoxins (e.g.…”

“…There are six a subunits (al-a6), three , subunits (/1 -/13), three y subunits (y1-y3) and one a subunit gene(s) . These genes are differentially expressed throughout the brain including the hypothalamus , and GABAergic regulation of the hypothalamus is well established (reviewed in Van den Pol et al 1990). As for EAA ionotropic receptors, it is difficult to be precisely sure of the in vivo subunit combinations.…”