Effects of chronic food restriction on prodynorphin-derived peptides in rat brain regions.
Chronic food restriction produces a variety of physiological and behavioral adaptations including a potentiation of the reinforcing effect of food, drugs and lateral hypothalamic electrical stimulation. Previous work in this laboratory has revealed that the lowering of self-stimulation threshold by food restriction is reduced by mu- and kappa-selective opioid antagonists. In the present study, the effect of chronic food restriction on levels of three prodynorphin-derived peptides, namely dynorphin A1-17 (A1-17), dynorphin A1-8 (A1-8) and dynorphin B1-13 (B1-13) were measured in eleven brain regions known to be involved in appetite, taste and reward. Food restriction increased levels of A1-17 in dorsal medial (+19.6%), ventral medial (+24.2%) and medial preoptic (+82.9%) hypothalamic areas. Levels of A1-17 decreased in the central nucleus of the amygdala (-35.1%). Food restriction increased levels of A1-8 in nucleus accumbens (+34.4%), bed nucleus of the stria terminalis (+24.5%) and lateral hypothalamus (+41.9%). Food restriction had no effect on levels of B1-13. A1-17 is highly kappa-preferring and the brain regions in which levels increased all have a high ratio of kappa: mu and delta receptors. A1-8 is less discriminating among opioid receptor types and the brain regions in which levels increased have a low ratio of kappa: mu and delta receptors. The present results suggest that food restriction alters posttranslational processing within the dynorphin A domain of the prodynorphin precursor, possibly leading to a change in the balance between kappa and non-kappa opioid receptor stimulation in specific brain regions.
Berman
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Department of Psychiatry, New York University Medical Center, NY 10016.
Devi
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Carr
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D000818:Animals; D004032:Diet; D004399:Dynorphins / Q000378:metabolism; D004745:Enkephalins / Q000378:metabolism*; D007028:Hypothalamic Hormones / Q000378:metabolism; D008297:Male; D009479:Neuropeptides / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D004745:Enkephalins; D007028:Hypothalamic Hormones; D009479:Neuropeptides; D010446:Peptide Fragments; D011498:Protein Precursors; C092588:dynorphin B (1-13); D004399:Dynorphins; C026770:dynorphin (1-8); C033660:preproenkephalin