Aims: 

The nucleus accumbens (NAcc), a key structure of the forebrain limbic circuitry, is known to play important roles in the central regulation of feeding and metabolism. Although the glucose-monitoring (GM) neurons here have already been shown to be intimately involved in these functions, our knowledge is limited yet about the endogenous and exogenous chemical sensitivities of these chemosensory cells.

Methods: 

In the present experiments, male Wistar and Sprague-Dawley rats were used. Extracellular single neuron activity was recorded in the NAcc by means of tungsten wire multibarreled glass microelectrodes, during 1) microelectrophoretic administration of various chemicals (D-glucose, NA, DA, Ach, and others), 2) gustatory stimulations (with the five primary qualities and orange juice as a complex stimulus), and 3) intragastric infusion of monosodium-L-glutamate (MSG), D-glucose, and NaCl.

Results: 

Appx. 25% of all neurons tested changed their activity in response to the microelectrophoretic administration of D-glucose. More than one third of these GM neurons changed in firing rate during intraoral taste stimulations. In case of intragastric infusions, short and long term effects have been recorded. In a few cells, the intraorally delivered sucrose or MSG has altered the neuronal responsiveness to intragastrically applied glucose or MSG.

Conclusion: 

Our present findings, along with previous data, demonstrate multiple functional attributes of GM neurons in the NAcc. These chemosensory cells, by the integration of chemical (and other) signals arising from the endogenous and exogenous environments, appear to play crucial role in adaptive mechanisms of the organization of feeding.

Support: 

Ajinomoto 51064/2009, OTKA K 68431, and HAS