Extracellular glutamate increases in the lateral hypothalamus during meal initiation and GABA peaks during satiation: Microdialysis measurement every 30 s.

Abstract

Glutamate injected into the lateral hypothalamus can initiate eating, and gamma-aminobutyric acid (GABA) can stop it. This leads to the hypothesis that glutamate inputs are active at the beginning of a meal, and GABA is released at the end. To test this theory, the authors used microdialysis to sample glutamate and GABA simultaneously before, during, and after a meal. Food-deprived rats ate a meal of chow. Glutamate increased during the first third of the meal, then decreased to below baseline while the rats were still eating. GABA also increased at the start of the meal but continued rising and peaked during the last third of the meal. Glutamate may drive a hypothalamic system for eating, and GABA may oppose it.

Bidirectional Dopaminergic Modulation of Excitatory Synaptic Transmission in Orexin Neurons

“…Orexin neurons exist in the brain area where injection of excitatory transmitter elicits intense feeding (Stanley et al, 1993) and endogenous glutamate release occurs during meal initiation (Rada et al, 2003). Collectively, DA may modulate excitatory transmission to alter the activity of orexin neurons.…”

A novel method for simultaneous glutamate and extracellular activity measurement in brain slices with high temporal resolution

“…Schematic view of the incubation chamber utilized for 30 carrying out the reaction to derive the fluorescent product "resorufin", which is detected in the fluorescence cell component 6 (B). In C a schematic of the entire system including the reaction chamber (7), syringe pump for introducing the enzymatic reactor and perfusate (8), the heating pad controller (9), the laser beam generator and its power supply (10), the CCD detector and the data integration processed by a computer (11). …”

“…For example, it provides information on a time scale considerably slower than many dynamic processes in the CNS and has a low temporal response, with sample collection times typically varying from 1 to 30 min, although occasionally rapid sampling times down to a few seconds have been achieved [8][9]. Another disadvantage is the size of the probe, 250-500 μm in diameter, which induces extensive tissue damage [10].…”

The different effects of high-frequency stimulation of the nucleus accumbens shell and core on food consumption are possibly associated with different neural responses in the lateral hypothalamic area

“…Inactivation of the Acb-Sh, rather than the Acb-Co, decreased GABA release in its target nuclei and increased food intake, whereas activation of the Acb-Sh induced opposite effects Stratford and Kelley, 1997). In addition, the extracellular GABA level in the LHA acts as a mediator of satiety: it is low at the onset of eating, rises as the subjects eat, peaks at the offset of feeding, and is then maintained at high levels (Rada et al, 2003). Therefore, different anatomical projections from the Acb-Sh and Acb-Co might explain the possible mechanisms of their different effects on feeding behavior (Groenewegen et al, 1999;Duva et al, 2005;Georgescu et al, 2005;van Dongen et al, 2005).…”