Abstract
The rat posterodorsal medial amygdala (MePD) is responsive to the orexigenic neuropeptide Y (NPY) and is a putative candidate to participate in neural circuits that modulate feeding behavior. Here, we studied the effects of intracerebroventricular (icv) microinjection of NPY on the appetitive and food intake behaviors of rats under the paradigm of the self-selection macronutrient isolated diets [high-carbohydrate (high-CHO), high-protein and high-lipid food pellets]. At the same time, Fos expression was also evaluated in the MePD as a marker of local cellular activation. Adult male rats received icv microinjections of NPY (1mg and10mg/5mL, n = 10 and 8, respectively) whereas the control groups either received icv microinjection of artificial cerebrospinal fluid (5mL, n = 8) or underwent sham procedure (n = 8). The data were obtained after a fasting protocol. Feeding behavior was evaluated during a 2 h test period of free access to the selective diets. Rats in all groups preferred the high-CHO diet. Compared to controls, both doses of NPY increased the appetitive behaviors (searching for food and the frequency of attempts to eat any diet) and the percentage of animals eating high-CHO diet. However, only NPY at a dose of 1 μg led to a significant increase in food intake and showed a strong positive correlation with Fos expression in the MePD (p 0.05 in all cases). These new data reveal a biphasic effect of NPY on the appetite and food intake behaviors and suggest that the MePD participates in the NPY-induced feeding behavior in rats.
Highlights
Multiple neural systems control food intake, body weight and energy homeostasis in rats [1,2,3,4]
The rat posterodorsal medial amygdala (MePD) is responsive to the orexigenic neuropeptide Y (NPY) and is a putative candidate to participate in neural circuits that modulate feeding behavior
These new data reveal a biphasic effect of NPY on the appetite and food intake behaviors and suggest that the MePD participates in the NPY-induced feeding behavior in rats
Summary
Multiple neural systems control food intake, body weight and energy homeostasis in rats [1,2,3,4]. The central organization of feeding behavior—cue-induced feeding, associative learning, decision-making, reward and feed-back modulation of appetite, eating and satiety—involves various classical neurotransmitters, neuropeptides and hormones for motivation [3,4,5,6]. Glutamate, the main excitatory neurotransmitter, increases food intake when microinjected in the lateral nucleus of the hypothalamus [7,8], and the activation of glutamatergic NMDA receptors is needed for the orexigenic effects of
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