There exist three main types of endogenous opioid peptides, enkephalins, dynorphins and β-endorphin, all of which are derived from their precursors. These endogenous opioid peptides act through opioid receptors, including mu opioid receptor (MOR), delta opioid receptor (DOR) and kappa opioid receptor (KOR), and play important roles not only in analgesia, but also many other biological processes such as reward, stress response, feeding and emotion. The MOR gene, OPRM1, undergoes extensive alternative pre-mRNA splicing, generating multiple splice variants or isoforms.
View Article and Find Full Text PDFConditioned flavor preferences are elicited by fat (Intralipid) in inbred mouse strains with BALB/c and SWR mice displaying among the most robust preferences. Dopamine D and opioid receptor antagonism differentially reduces the acquisition (learning) and expression (maintenance) of fat-conditioned flavor preferences in these two strains. Because noncompetitive NMDA receptor antagonism with MK-801 differentially altered sugar-conditioned flavor preferences in these strains, and because NMDA receptors are involved in fat intake, the present study examined whether MK-801 differentially altered expression and acquisition of fat (Intralipid)-conditioned flavor preferences in BALB/c and SWR mice.
View Article and Find Full Text PDFConditioned flavor preferences (CFP) are elicited by sucrose and fructose relative to saccharin in rats and inbred mice. Whereas dopamine, but not opioid receptor antagonists interfere with the acquisition (learning) and expression (maintenance) of sugar-CFP in rats, these antagonists differentially affect acquisition and expression of sucrose- and fructose-CFP in BALB/c and SWR inbred mice. Given that NMDA receptor antagonism with MK-801 blocks acquisition, but not expression of fructose-CFP in rats, the present study examined whether MK-801 altered the expression and acquisition of sucrose- and fructose-CFP in BALB/c and SWR mice.
View Article and Find Full Text PDFRecent studies indicate that C57BL/6J (B6) and FVB inbred mouse strains differ in post-oral fructose conditioning. This was demonstrated by their differential flavor conditioning response to intragastric fructose and their preference for fructose versus a non-nutritive sweetener. The present study extended this analysis to SWR and BALB/c inbred strains which are of interest because they both show robust flavor conditioning responses to fructose.
View Article and Find Full Text PDFSugar appetite is influenced by unlearned and learned preferences in rodents. The present study examined whether dopamine (DA) D1 (SCH23390: SCH) and opioid (naltrexone: NTX) receptor antagonists differentially altered the expression and acquisition of fructose-conditioned flavor preferences (CFPs) in BALB/c and SWR mice. In expression experiments, food-restricted mice alternately (10 sessions, 1h) consumed a flavored (e.
View Article and Find Full Text PDFSugar and fat intake in rodents are mediated in part by brain dopamine (DA) and opioid neurotransmitter systems although important strain differences exist. Thus, whereas sucrose intake of BALB/c and SWR mice was reduced by DA D1 (SCH23390: SCH) receptor antagonism, opioid (naltrexone: NTX) receptor antagonism reduced intake only in BALB/c mice. Both SCH and NTX reduced fat (Intralipid) intake in SWR, but not BALB/c mice.
View Article and Find Full Text PDFIn a large (250 registrants) general education lecture course, neuroscience principles were taught by two professors as co-instructors, starting with simple brain anatomy, chemistry, and function, proceeding to basic brain circuits of pleasure and pain, and progressing with fellow expert professors covering relevant philosophical, artistic, marketing, and anthropological issues. With this as a base, the course wove between fields of high relevance to psychology and neuroscience, such as food addiction and preferences, drug seeking and craving, analgesic pain-inhibitory systems activated by opiates and stress, neuroeconomics, unconscious decision-making, empathy, and modern neuroscientific techniques (functional magnetic resonance imaging and event-related potentials) presented by the co-instructors and other Psychology professors. With no formal assigned textbook, all lectures were PowerPoint-based, containing links to supplemental public-domain material.
View Article and Find Full Text PDFSugar and fat appetites are influenced by unlearned and learned responses to orosensory and post-ingestive properties which are mediated by dopamine (DA) and opioid transmitter systems. In BALB and SWR mice, acquisition and expression of sucrose conditioned flavor preferences (CFP) are differentially affected by systemic DA D1 (SCH23390: SCH) and opioid (naltrexone: NTX) antagonism. The present study examined whether fat-CFP occurred in these strains using preferred (5%) and less preferred (0.
View Article and Find Full Text PDFSugar appetite is influenced by unlearned attractions to sweet taste and learned responses to sugars' taste and post-ingestive actions. In rats, sugar-conditioned flavor preferences (CFP) are attenuated by dopamine D1 (SCH23390: SCH), but not by opioid (naltrexone: NTX), receptor antagonism. Sucrose-CFP occurs in BALB/c and SWR inbred mice that differ in their suppressive effects of SCH and NTX on sucrose intake.
View Article and Find Full Text PDFPreference for and intake of solid and emulsified fat (intralipid) solutions vary across different mouse strains. Fat intake in rodents is inhibited by dopamine and opioid receptor antagonists, but any variation in these responses as a function of genetic background is unknown. Therefore, the present study compared the ability of dopamine D1-like (SCH23390) and general opioid (naltrexone) receptor antagonism to alter intake of fat emulsions (intralipid) in mice.
View Article and Find Full Text PDF