Thus NPY act as a resilience factor by impairing associative implicit memory after stressful and aversive events, as evident in models of fear conditioning, presumably via Y1 receptors in the amygdala and prefrontal cortex. NPY can exert both inhibitory and stimulatory effects on memory, depending on memory type and phase, dose applied, brain region, and NPY receptor subtypes. Here these results are presented in relation to the types of memory affected by NPY and its receptors. Therefore it is not surprising that an increasing number of studies have provided evidence for NPY acting as a modulator of neuroplasticity, neurotransmission, and memory. High levels of NPY expression in brain regions important for learning and memory together with its neuromodulatory and neurotrophic effects suggest a regulatory role for NPY in memory processes.
Given the role of neurotrophins in the hypothalamus, these findings, although preliminary, provide evidence for a role of NPY as inhibitor of HPA axis and support the idea that NPY might be involved in pathologies characterized by HPA axis dysfunctions. We found that NPY treatment decreased BDNF and increased NGF production in the hypothalamus. To characterize the effect of NPY on the production of neurotrophins in the hypothalamus we exposed young adult rats to NPY intraperitoneal administration for three consecutive days and then evaluated BDNF and NGF synthesis in this brain region. In addition to this, a possible role of neurotrophins, particularly BDNF, in HPA axis hyperactivation has been proposed. The neurotrophins brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) are proteins involved in the growth, survival and function of neurons. Among NPY actions preclinical and clinical data have suggested that the anxiolytic and antidepressant actions of NPY may be related to its antagonist action on the hypothalamic-pituitary-adrenal (HPA) axis. Neuropeptide Y ( NPY) is a 36-amino acid peptide which exerts several regulatory actions within peripheral and central nervous systems. Gelfo, Francesca De Bartolo, Paola Tirassa, Paola Croce, Nicoletta Caltagirone, Carlo Petrosini, Laura Angelucci, Francesco Intraperitoneal injection of neuropeptide Y ( NPY) alters neurotrophin rat hypothalamic levels: Implications for NPY potential role in stress-related disorders. Taken together, our findings suggest that NPY expressed by distinct populations of neurons can modulate afferent and efferent projections of the CEA via presynaptic Y2 receptors located at inhibitory and excitatory synapses. However, we also provide evidence that lack of NPY or Y2 receptors results in increased GABA release specifically at inhibitory synapses in the CEm. Functionally, the Y2 receptor agonist PYY3-36, reduced both, inhibitory as well as excitatory synaptic transmission in the centromedial amygdala (CEm). Retrograde tract tracing experiments revealed that NPY neurons reciprocally connect the CEA and BNST. Interestingly, NPY neurons did not co-localize with the Y2 receptor. Furthermore, in the main intercalated nucleus, NPY is expressed primarily in dopamine D1 receptor-expressing neurons but also in interspersed somatostatin-expressing neurons. We identified several NPY-expressing neuronal populations, including somatostatin- and calretinin-expressing neurons. Here, we characterized the expression, connectivity and electrophysiological function of NPY and Y2 receptors within the CEA. Among these, neuropeptide Y ( NPY) has emerged as an important anxiolytic and fear-reducing neuromodulator. Both, CEA and BNST contain high amounts of different neuropeptides that significantly contribute to synaptic transmission. In particular, the central extended amygdala, consisting of the central amygdala (CEA) and the bed nucleus of the stria terminalis (BNST) is an essential component actively controlling efferent connections to downstream effectors like hypothalamus and brain stem.
It consists of several nuclei with highly selective, elaborate functions. The amygdala is essential for generating emotional-affective behaviors. Wood, J Verma, D Lach, G Bonaventure, P Herzog, H Sperk, G Tasan, R O Structure and function of the amygdaloid NPY system: NPY Y2 receptors regulate excitatory and inhibitory synaptic transmission in the centromedial amygdala.
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