RESUMO
Ghrelin, a stomach-derived orexigenic hormone, has a well-established role in energy homeostasis, food reward, and emotionality. Noradrenergic neurons of the locus coeruleus (LC) are known to play an important role in arousal, emotion, cognition, but recently have also been implicated in control of feeding behavior. Ghrelin receptors (the growth hormone secretagogue receptor, GHSR) may be found in the LC, but the behavioral effects of ghrelin signaling in this area are still unexplored. Here, we first determined whether GHSR are present in the rat LC, and demonstrate that GHSR are expressed on noradrenergic neurons in both sexes. We next investigated whether ghrelin controls ingestive and motivated behaviors as well as anxiety-like behavior by acting in the LC. To pursue this idea, we examined the effects of LC GHSR stimulation and blockade on food intake, operant responding for a palatable food reward and, anxiety-like behavior in the open field (OF) and acoustic startle response (ASR) tests in male and female rats. Our results demonstrate that intra-LC ghrelin administration increases chow intake and motivated behavior for sucrose in both sexes. Additionally, females, but not males, exhibited a potent anxiolytic response in the ASR. In order to determine whether activation of GHSR in the LC was necessary for feeding and anxiety behavior control, we utilized liver-expressed antimicrobial peptide 2 (LEAP2), a newly identified endogenous GHSR antagonist. LEAP2 delivered specifically into the LC was sufficient to reduce fasting-induced chow hyperphagia in both sexes, but food reward only in females. Moreover, blockade of GHSR in the LC increased anxiety-like behavior measured in the ASR test in both sexes. Taken together, these results indicate that ghrelin acts in the LC to alter ingestive, motivated and anxiety-like behaviors, with a degree of sex divergence.
RESUMO
ABSTRACT: Fresh produce continues to be the main source of foodborne illness outbreaks in the United States, implicating bacterial pathogens such as Escherichia coli O157:H7 (EHEC). The efficacy of nanoemulsified carvacrol (NCR) as a washing treatment in reducing EHEC on fresh produce was investigated. Fresh baby spinach, romaine lettuce, and iceberg lettuce leaves (2.5-cm-diameter cores) were spot inoculated with a five-strain cocktail of nalidixic acid-resistant EHEC at â¼6 log CFU/cm2. After air drying for 1 h, 20 pieces of each inoculated produce leaf were immersed in water-based treatment solutions (200 mL per group), including water alone, 25 or 50 ppm of free chlorine, and 0.25 or 0.75% NCR for 2 min. Inoculated produce leaves without any treatment served as baseline. Produce leaves were stored at 10°C, and surviving EHEC populations were enumerated on days 0, 2, 7, and 14. The viability of EHEC following NCR treatments on the fresh produce was visualized under a fluorescence microscope. NCR treatment at 0.75% immediately reduced EHEC populations on iceberg lettuce by 1.3 log CFU/cm2 as compared with the produce treated with water alone (P < 0.05). Antimicrobial activity of NCR against EHEC was comparable to chlorine treatments on day 0 for all produce (P > 0.05). After 14 days of storage at 10°C, populations of EHEC on 0.75% NCR-treated romaine lettuce were reduced by 2.3 log CFU/cm2 compared with the recovery from 50 ppm of chlorine-treated samples (P < 0.05). Microscopic images revealed that EHEC cells were observed to be clustered on the baseline samples, indicating the development of cell aggregation, compared with the scattered cells seen on NCR-treated leaf surfaces. Treatments with NCR did not significantly affect the color of the fresh produce leaves during 14 days of storage at 10°C. Results of this study support the potential use of NCR as a water-soluble natural antimicrobial wash treatment for controlling EHEC on fresh produce.
