Nucleus accumbens mu-opioids regulate intake of a high-fat diet via activation of a distributed brain network.

Endogenous opioid peptides within the nucleus accumbens, a forebrain site critical for the regulation of reward-related behavior, are believed to play an important role in the control of appetite. In particular, this system is thought to mediate the hedonic aspects of food intake, governing the positive emotional response to highly palatable food such as fat and sugar. Previous work has shown that intra-accumbens administration of the mu-opioid agonist D-Ala2,Nme-Phe4,Glyol5-enkephalin (DAMGO) markedly increases food intake and preferentially enhances the intake of palatable foods such as fat, sucrose, and salt. Using information from recently performed c-fos mapping experiments, we sought to explore the involvement of structures efferent to the nucleus accumbens in this feeding response. Free-feeding rats with dual sets of bilateral cannulas aimed at the nucleus accumbens and one of several output structures were infused with DAMGO (0, 0.25 microg/0.5 microl) in the accumbens, and fat intake was measured over a 2 hr period. Concurrent temporary inactivation with the GABA(A) agonist muscimol (5-20 ng/0.25 microl) of the dorsomedial hypothalamic nucleus, lateral hypothalamus, ventral tegmental area, or the intermediate region of the nucleus of the solitary tract blocked the robust increase in fat intake induced by intra-accumbens DAMGO at doses of muscimol that did not affect general motor activity. Muscimol alone also inhibited and augmented baseline fat intake in the lateral and dorsomedial hypothalamic nuclei, respectively. These results suggest that intake of energy-dense palatable food is controlled by activity in a neural network linking ventral striatal opioids with diencephalic and brainstem structures.

Remote measurement of NO2 in the brown cloud over Albuquerque, New Mexico.

Remote measurements of nitrogen dioxide (NO2) were recorded in the 'brown cloud' over Albuquerque, NM, using absorption spectroscopy in the winter of 1987-88 and summer of 1989. The NO2 burdens (optical densities) measured in this manner were found to be in excess of 100 ppm-m. These long pathlength measurements correspond to total concentrations of approximately 5-10 ppb over the integrated observation pathlengths, which ranged from 10-20 km. These concentrations compare well with single location, independent NO x analyses. Using two correlation (absorption) spectrometers simultaneously, it was shown that the NO2 distribution is not uniform over the city and can change on the order of minutes in the boundary layer late in the day, demonstrating the advantages of NO2 optical measurements for assessing the location and extent of urban nitrogen dioxide levels in the boundary layer.