Food Deprivation-induced Increases Research Articles

Central ghrelin increases food foraging/hoarding that is blocked by GHSR antagonism and attenuates hypothalamic paraventricular nucleus neuronal activation.

The stomach-derived "hunger hormone" ghrelin increases in the circulation in direct response to time since the last meal, increasing preprandially and falling immediately following food consumption. We found previously that peripheral injection of ghrelin potently stimulates food foraging (FF), food hoarding (FH), and food intake (FI) in Siberian hamsters. It remains, however, largely unknown if central ghrelin stimulation is necessary/sufficient to increase these behaviors regardless of peripheral stimulation of the ghrelin receptor [growth hormone secretagogue receptor (GHSR)]. We injected three doses (0.01, 0.1, and 1.0 μg) of ghrelin into the third ventricle (3V) of Siberian hamsters and measured changes in FF, FH, and FI. To test the effects of 3V ghrelin receptor blockade, we used the potent GHSR antagonist JMV2959 to block these behaviors in response to food deprivation or a peripheral ghrelin challenge. Finally, we examined neuronal activation in the arcuate nucleus and paraventricular hypothalamic nucleus in response to peripheral ghrelin administration and 3V GHSR antagonism. Third ventricular ghrelin injection significantly increased FI through 24 h and FH through day 4. Pretreatment with 3V JMV2959 successfully blocked peripheral ghrelin-induced increases in FF, FH, and FI at all time points and food deprivation-induced increases in FF, FH, and FI up to 4 h. c-Fos immunoreactivity was significantly reduced in the paraventricular hypothalamic nucleus, but not in the arcuate nucleus, following pretreatment with intraperitoneal JMV2959 and ghrelin. Collectively, these data suggest that central GHSR activation is both necessary and sufficient to increase appetitive and consummatory behaviors in Siberian hamsters.

PYY(3-36) into the arcuate nucleus inhibits food deprivation-induced increases in food hoarding and intake

Central administration of neuropeptide Y (NPY) increases food intake in laboratory rats and mice, as well as food foraging and hoarding in Siberian hamsters. The NPY-Y1 and Y5 receptors (Rs) within the hypothalamus appear sufficient to account for these increases in ingestive behaviors. Stimulation of NPY-Y2Rs in the Arcuate nucleus (Arc) has an anorexigenic effect as shown by central or peripheral administration of its natural ligand peptide YY (3-36) and pharmacological NPY-Y2R antagonism by BIIE0246 increases food intake. Both effects on food intake by NPY-Y2R agonism and antagonism are relatively short-lived lasting ∼4h. The role of NPY-Y2Rs in appetitive ingestive behaviors (food foraging/hoarding) is untested, however. Therefore, Siberians hamsters, a natural food hoarder, were housed in a semi-natural burrow/foraging system that had (a) foraging requirement (10 revolutions/pellet), no free food (true foraging group), (b) no running wheel access, free food (general malaise control) or (c) running wheel access, free food (exercise control). We microinjected BIIE0246 (antagonist) and PYY(3-36) (agonist) into the Arc to test the role of NPY-Y2Rs there on ingestive behaviors. Food foraging, hoarding, and intake were not affected by Arc BIIE0246 microinjection in fed hamsters 1, 2, 4, and 24h post injection. Stimulation of NPY-Y2Rs by PYY(3-36) inhibited food intake at 0–1 and 1–2h and food hoarding at 1–2h without causing general malaise or affecting foraging. Collectively, these results implicate a sufficiency, but not necessity, of the Arc NPY-Y2R in the inhibition of food intake and food hoarding by Siberian hamsters.

Anti-ghrelin Spiegelmer inhibits exogenous ghrelin-induced increases in food intake, hoarding, and neural activation, but not food deprivation-induced increases

Circulating concentrations of the stomach-derived "hunger-peptide" ghrelin increase in direct proportion to the time since the last meal. Exogenous ghrelin also increases food intake in rodents and humans, suggesting ghrelin may increase post-fast ingestive behaviors. Food intake after food deprivation is increased by laboratory rats and mice, but not by humans (despite dogma to the contrary) or by Siberian hamsters; instead, humans and Siberian hamsters increase food hoarding, suggesting the latter as a model of fasting-induced changes in human ingestive behavior. Exogenous ghrelin markedly increases food hoarding by ad libitum-fed Siberian hamsters similarly to that after food deprivation, indicating sufficiency. Here, we tested the necessity of ghrelin to increase food foraging, food hoarding, and food intake, and neural activation [c-Fos immunoreactivity (c-Fos-ir)] using anti-ghrelin Spiegelmer NOX-B11-2 (SPM), an l-oligonucleotide that specifically binds active ghrelin, inhibiting peptide-receptor interaction. SPM blocked exogenous ghrelin-induced increases in food hoarding the first 2 days after injection, and foraging and food intake at 1-2 h and 2-4 h, respectively, and inhibited hypothalamic c-Fos-ir. SPM given every 24 h across 48-h food deprivation inconsistently inhibited food hoarding after refeeding and c-Fos-ir, similarly to inabilities to do so in laboratory rats and mice. These results suggest that ghrelin may not be necessary for food deprivation-induced foraging and hoarding and neural activation. A possible compensatory response, however, may underlie these findings because SPM treatment led to marked increases in circulating ghrelin concentrations. Collectively, these results show that SPM can block exogenous ghrelin-induced ingestive behaviors, but the necessity of ghrelin for food deprivation-induced ingestive behaviors remains unclear.

Inhibition of ghrelin O-acyltransferase attenuates food deprivation-induced increases in ingestive behavior

Ghrelin is an orexigenic hormone produced by the stomach in direct proportion to the time since the last meal and has therefore been called a ‘hunger signal’. The octanoylation of ghrelin is critical for its orexigenic functions and is dependent upon ghrelin O-acyltransferase (GOAT) catalyzation. The GOAT inhibitor, GO-CoA-Tat, decreases the circulating concentrations of octanoylated ghrelin and attenuates weight gain on a high fat diet in mice. Unlike rats and mice, Siberian hamsters and humans do not increase food intake after food deprivation, but increase food hoarding after food deprivation. In Siberian hamsters, exogenous ghrelin increases ingestive behaviors similarly to 48–56h food deprivation. Therefore, we tested the necessity of increased ghrelin in food-deprived Siberian hamsters to stimulate ingestive behaviors. To do so we used our simulated natural housing system that allows hamsters to forage for and hoard food. Animals were given an injection of GO-CoA-Tat (i.p., 11μmol/kg) every 6h because that is the duration of its effective inhibition of octanoylated ghrelin concentrations during a 48h food deprivation. We found that GO-CoA-Tat attenuated food foraging (0–1h), food intake (0–1 and 2–4h), and food hoarding (0–1h and 2 and 3days) post-refeeding compared with saline treated animals. This suggests that increased octanoylated ghrelin concentrations play a role in the food deprivation-induced increases in ingestive behavior. Therefore, ghrelin is a critical aspect of the multi-faceted mechanisms that stimulate ingestive behaviors, and might be a critical point for a successful clinical intervention scheme in humans.

Neuroendocrine regulation of appetitive ingestive behavior

Food availability in nature is often irregular, and famine is commonplace. Increased motivation to engage in ingestive behaviors increases the chance of survival, providing additional potential opportunities for reproduction. Because of the advantages conferred by entraining ingestive behavior to environmental conditions, neuroendocrine mechanisms regulating the motivation to acquire and ingest food have evolved to be responsive to exogenous (i.e., food stored for future consumption) and endogenous (i.e., body fat stores) fuel availability. Motivated behaviors like eating occur in two phases. The appetitive phase brings animals into contact with food (e.g., foraging, food hoarding), and the more reflexive consummatory phase results in ingestion (e.g., chewing, swallowing). Quantifiable appetitive behaviors are part of the natural ingestive behavioral repertoire of species such as hamsters and humans. This review summarizes current knowledge about neuroendocrine regulators of ingestive behavior, with an emphasis appetitive behavior. We will discuss hormonal regulators of appetitive ingestive behaviors, including the orexigenic hormone ghrelin, which potently stimulates foraging and food hoarding in Siberian hamsters. This section includes a discussion of the hormone leptin, its relation to endogenous fat stores, and its role in food deprivation-induced increases in appetitive ingestive behaviors. Next, we discuss how hormonal regulators interact with neurotransmitters involved in the regulation of ingestive behaviors, such as neuropeptide Y (NPY), agouti-related protein (AgRP) and α-melanocyte stimulating hormone (α-MSH), to regulate ingestive behavior. Finally, we discuss the potential impact that perinatal nutrient availability can have on the neuroendocrine regulation of ingestive behavior. Understanding the hormonal mechanisms that connect metabolic fuel availability to central appetite regulatory circuits should provide a better understanding of the neuroendocrine regulation of the motivation to engage in ingestive behavior.

Neural and hormonal control of food hoarding

Many animals hoard food, including humans, but despite its pervasiveness, little is known about the physiological mechanisms underlying this appetitive behavior. We summarize studies of food hoarding in humans and rodents with an emphasis on mechanistic laboratory studies of species where this behavior importantly impacts their energy balance (hamsters), but include laboratory rat studies although their wild counterparts do not hoard food. The photoperiod and cold can affect food hoarding, but food availability is the most significant environmental factor affecting food hoarding. Food-deprived/restricted hamsters and humans exhibit large increases in food hoarding compared with their fed counterparts, both doing so without overeating. Some of the peripheral and central peptides involved in food intake also affect food hoarding, although many have not been tested. Ad libitum-fed hamsters given systemic injections of ghrelin, the peripheral orexigenic hormone that increases with fasting, mimics food deprivation-induced increases in food hoarding. Neuropeptide Y or agouti-related protein, brain peptides stimulated by ghrelin, given centrally to ad libitum-fed hamsters, duplicates the early and prolonged postfood deprivation increases in food hoarding, whereas central melanocortin receptor agonism tends to inhibit food deprivation and ghrelin stimulation of hoarding. Central or peripheral leptin injection or peripheral cholecystokinin-33, known satiety peptides, inhibit food hoarding. Food hoarding markedly increases with pregnancy and lactation. Because fasted and/or obese humans hoard more food in general, and more high-density/high-fat foods specifically, than nonfasted and/or nonobese humans, understanding the mechanisms underlying food hoarding could provide another target for behavioral/pharmacological approaches to curb obesity.

Arcuate nucleus destruction does not block food deprivation-induced increases in food foraging and hoarding

The mechanisms underlying the control of food intake are considerably better understood than those underlying the appetitive ingestive behaviors of foraging and hoarding of food, despite the prevalence of the latter across species including humans. Neuropeptide Y (NPY) and Agouti-related protein (AgRP), two orexigenic neuropeptides known to stimulate food intake in a variety of species, applied centrally to Siberian hamsters increases foraging and especially hoarding with lesser increases in food intake. Both are expressed in the arcuate nucleus (Arc) and their synthesis increases with food deprivation, a naturally-occurring stimulus that markedly increases foraging and hoarding in Siberian hamsters. Therefore, we tested whether destruction of Arc neurons blocks these ingestive behaviors. This was accomplished either by microinjecting NPY conjugated to saporin (NPY-SAP) bilaterally into the Arc to kill NPY receptor-bearing neurons or via neonatal monosodium glutamate (MSG) treatment. For both methods, Arc cresyl violet staining (cell density) and NPY and Y1 receptor-immunoreactivity (ir) were significantly decreased. Although baseline foraging and food hoarding were not affected, food deprivation-induced increased food hoarding was surprisingly exaggerated ∼ 100% with both types of Arc destruction. We found a substantial amount of remaining NPY-ir fibers, likely emanating from the brainstem, and a significant up-regulation of Y1 receptors in Arc NPY projections areas (hypothalamic paraventricular nucleus and perifornical area) after Arc denervation and their activation may have accounted for the exaggerated increases. The converging evidence from both Arc destruction methods suggests an intact Arc is not necessary for food deprivation-induced increases in food foraging and hoarding.

Cholecystokinin-33 acutely attenuates food foraging, hoarding and intake in Siberian hamsters

Neurochemicals that stimulate food foraging and hoarding in Siberian hamsters are becoming more apparent, but we do not know if cessation of these behaviors is due to waning of excitatory stimuli and/or the advent of inhibitory factors. Cholecystokinin (CCK) may be such an inhibitory factor as it is the prototypic gastrointestinal satiety peptide and is physiologically important in decreasing food intake in several species including Siberian hamsters. Systemic injection of CCK-33 in laboratory rats decreases food intake, doing so to a greater extent than CCK-8. We found minimal effects of CCK-8 on food foraging and hoarding previously in Siberian hamsters, but have not tested CCK-33. Therefore, we asked: Does CCK-33 decrease normal levels or food deprivation-induced increases in food foraging, hoarding and intake? Hamsters were housed in a wheel running-based foraging system with simulated burrows to test the effects of peripheral injections of CCK-33 (13.2, 26.4, or 52.8 μg/kg body mass), with or without a preceding 56 h food deprivation. The highest dose of CCK-33 caused large baseline reductions in all three behaviors for the 1st hour post-injection compared with saline; in addition, the intermediate CCK-33 dose was sufficient to curtail food intake and foraging during the 1st hour. In food-deprived hamsters, we used a 52.8 μg/kg body mass dose of CCK-33 which decreased food intake, hoarding, and foraging almost completely compared with saline controls for 1 h. Therefore, CCK-33 appears to be a potent inhibitor of food intake, hoarding, and foraging in Siberian hamsters.

Leptin inhibits food-deprivation-induced increases in food intake and food hoarding

Food deprivation stimulates foraging and hoarding and to a much lesser extent, food intake in Siberian hamsters. Leptin, the anorexigenic hormone secreted primarily from adipocytes, may act in the periphery, the brain, or both to inhibit these ingestive behaviors. Therefore, we tested whether leptin given either intracerebroventricularly or intraperitoneally, would block food deprivation-induced increases in food hoarding, foraging, and intake in animals with differing foraging requirements. Hamsters were trained in a running wheel-based food delivery foraging system coupled with simulated burrow housing. We determined the effects of food deprivation and several peripheral doses of leptin on plasma leptin concentrations. Hamsters were then food deprived for 48 h and given leptin (0, 10, 40, or 80 microg ip), and additional hamsters were food deprived for 48 h and given leptin (0, 1.25, 2.5, or 5.0 microg icv). Foraging, food intake, and hoarding were measured postinjection. Food deprivation stimulated food hoarding to a greater degree and duration than food intake. In animals with a foraging requirement, intracerebroventricular leptin almost completely blocked food deprivation-induced increased food hoarding and intake, but increased foraging. Peripheral leptin treatment was most effective in a sedentary control group, completely inhibiting food deprivation-induced increased food hoarding and intake at the two highest doses, and did not affect foraging at any dose. Thus, the ability of leptin to inhibit food deprivation-induced increases in ingestive behaviors differs based on foraging effort (energy expenditure) and the route of administration of leptin administration.

Arcuate nucleus destruction does not block food deprivation-induced increases in food foraging and hoarding

The mechanisms underlying the control of food intake are considerably better understood than those underlying the appetitive ingestive behaviors of foraging and hoarding of food, despite the prevalence of the latter across species including humans. Neuropeptide Y (NPY) and Agouti-related protein (AgRP), two orexigenic neuropeptides known to stimulate food intake in a variety of species, applied centrally to Siberian hamsters increases foraging and especially hoarding with lesser increases in food intake. Both are expressed in the arcuate nucleus (Arc) and their synthesis increases with food deprivation, a naturally-occurring stimulus that markedly increases foraging and hoarding in Siberian hamsters. Therefore, we tested whether destruction of Arc neurons blocks these ingestive behaviors. This was accomplished either by microinjecting NPY conjugated to saporin (NPY-SAP) bilaterally into the Arc to kill NPY receptor-bearing neurons or via neonatal monosodium glutamate (MSG) treatment. For both methods, Arc cresyl violet staining (cell density) and NPY and Y1 receptor-immunoreactivity (ir) were significantly decreased. Although baseline foraging and food hoarding were not affected, food deprivation-induced increased food hoarding was surprisingly exaggerated approximately 100% with both types of Arc destruction. We found a substantial amount of remaining NPY-ir fibers, likely emanating from the brainstem, and a significant up-regulation of Y1 receptors in Arc NPY projections areas (hypothalamic paraventricular nucleus and perifornical area) after Arc denervation and their activation may have accounted for the exaggerated increases. The converging evidence from both Arc destruction methods suggests an intact Arc is not necessary for food deprivation-induced increases in food foraging and hoarding.

MTII attenuates ghrelin- and food deprivation-induced increases in food hoarding and food intake

Food deprivation triggers a constellation of physiological and behavioral changes including increases in peripherally-produced ghrelin and centrally-produced agouti-related protein (AgRP). Upon refeeding, food intake is increased in most species, however hamsters primarily increase food hoarding. Food deprivation-induced increases in food hoarding by Siberian hamsters are mimicked by peripheral ghrelin and central AgRP injections. Because food deprivation stimulates ghrelin as well as AgRP synthesis/release, food deprivation-induced increases in hoarding may be mediated by melanocortin 3 or 4 receptor (MC3/4-R) antagonism via AgRP, the MC3/4-R inverse agonist. Therefore, we asked: Can a MC3/4-R agonist block food deprivation- or ghrelin-induced increases in foraging, food hoarding and food intake? This was accomplished by injecting melanotan II (MTII), a synthetic MC3/4-R agonist, into the 3rd ventricle in food deprived, fed or peripheral ghrelin injected hamsters and housed in a running wheel-based food delivery foraging system. Three foraging conditions were used: a) no running wheel access, non-contingent food, b) running wheel access, non-contingent food or c) a foraging requirement for food (10 revolutions/pellet). Food deprivation was a more potent stimulator of foraging and hoarding than ghrelin. Concurrent injections of MTII completely blocked food deprivation- and ghrelin-induced increases in food intake and attenuated, but did not always completely block, food deprivation- and ghrelin-induced increases in food hoarding. Collectively, these data suggest that the MC3/4-R are involved in ghrelin- and food deprivation-induced increases in food intake, but other neurochemical systems, such as previously demonstrated with neuropeptide Y, also are involved in increases in food hoarding as well as foraging.

The melanocortin system as a central integrator of direct and indirect controls of food intake

the neural control of food intake and body weight is a complex function in which cognitive and emotional variables, as well as long-term signals of metabolic status and fuel storage, are integrated with short-term signals related to individual meals. Several years ago, Smith ([20][1]) proposed a

Metabolic signals, hormones and neuropeptides involved in control of energy balance and reproductive success in hamsters.

In the 'postgenome era', most research on the neuroendocrine control of energy homeostasis has focused on hormonal and neuropeptide control of food intake (i.e. the amount of food eaten) in rats and mice. The amount of food consumed is influenced by both the motivation to procure food and the consummatory act of ingestion. In some species, the rate of food intake remains relatively constant, while survival is maintained via changes in food procurement, external storage and internal expenditure. For example, in hamsters, metabolic signals, peripheral hormones and central neuropeptides influence hunger motivation, food hoarding and changes in energy expenditure without necessarily influencing the amount of food ingested. A similar suite of metabolic signals, hormones and neuropeptides is involved in optimizing reproductive success under fluctuating energetic conditions. Reproductive processes are inhibited or delayed when energy expenditure outstrips energy intake and mobilization from storage. Estrous cyclicity in Syrian hamsters is sensitive to the availability of oxidizable glucose, but the presence of central glucose alone is not sufficient for normal estrous cycles. Food deprivation-induced anestrus does not depend upon food deprivation-induced increases in concentrations of adrenal hormones such as glucocorticoids. If hormones such as insulin and leptin play a role, they might do so by modulating the availability of glucose detected at extra-hypothalamic sites, instead of or in addition to direct effects on the mechanisms that control gonadotropin releasing hormone secretion. Despite our ability to measure and manipulate gene transcription, understanding of fuel homeostasis requires examination of indirect effects of hormones and neuropeptides on peripheral metabolism, attention to the motivational as well as consummatory aspects of ingestion, and the study of behaviour in a natural or seminatural context.

Food-deprivation increases cocaine-induced conditioned place preference and locomotor activity in rats.

Food-deprivation increases the reinforcing efficacy of cocaine and other drugs within self-administration experiments. In this study, the effects of food-deprivation on cocaine-induced conditioned place preference were investigated. Male Sprague-Dawley rats were assigned to one of two feeding conditions: satiated (with ad libitum food) or deprived (maintained at 80% of free-feeding body weights). During conditioning trials, on alternate days, rats received IP injections of cocaine (0.0, 2.5, 5.0, or 10.0 mg/kg; n = 12 per dose group) and were confined for 30 min in one of two distinct environments. On intervening days, the same rats were injected with saline and confined for 30 min in the opposite environment. After four cocaine and four saline trails, a 15-min choice test (with no injections) was given. During this time, the rats were able to move freely through a passageway between both environments. Relative to the food-satiated rats, the food-deprived rats showed a greater conditioned preference for the cocaine-paired environment during the choice test, greater cocaine-induced locomotor activity during conditioning trials, and a greater degree of sensitization to the activating effects of cocaine across conditioning trials. This study extends the general findings of food deprivation-induced increases in the reinforcing efficacy of cocaine to include the conditioned place preference paradigm.

Food deprivation-induced increases in hoarding by Siberian hamsters are not photoperiod-dependent

Siberian hamsters increase food hoarding in response to chronic food restriction and food deprivation, conditions that lead to a loss of body mass and fat. Therefore, the first purpose of the present experiments was to test further the effects of food deprivation on food hoarding by varying the length and order of repeated fasts to address the following questions: 1. Does the magnitude of the food-hoarding response increase as food deprivation length increases? 2, Is the effect of food deprivation on food hoarding experience-dependent? Second, we were interested in testing the effects of short winter-like days (SDs) on food hoarding. We tested this by measuring food hoarding in long days (LDs) and SDs during baseline conditions and after food deprivation to address the following question: Does SD exposure increase baseline and food deprivation-induced hoarding due to the naturally occurring SD-induced decreases in body fat? During each experiment, we were interested in determining how hamsters utilize their food hoard (i.e., add to it and eat from it). Our results extended those of our previous studies in showing that: 1. Food-deprivation length and the initial food-hoard size were not related to one another; 2. The maintenance of food-hoard size was proportional to the length of the fast; 3. The effects of a bout of food deprivation on food hoarding were dependent upon the lengths of previous fasts; 4. Baseline food hoarding was not different between LD- and SD-exposed hamsters; 5. The maintenance of food-hoard size, but not the initial fast-induced increases in food-hoard size, were increased in SDs; 6. Hamsters ate approximately 25–33% of their daily food intake from the food hoard under all conditions, with the degree of food replacement increasing as fast length was increased; and 7. The typical SD-induced decrease in food intake was reflected in the food eaten from the food supply found outside the burrow, but food eaten from the hoard was increased. Collectively, the results of the present experiments suggest that the initiation of food hoarding may be associated with short-term fluctuations in energy metabolism associated with fasting, but that the more long-term decreases in body mass (fat) are involved in the maintenance of food-hoard size.

The role of food deprivation in the maintenance and reinstatement of cocaine-seeking behavior in rats

Lever-pressing responses of a group of five rats (Group E) were rewarded with i.v. injections of cocaine (0.1 mg/kg) under conditions of continuous access for eleven 24-h sessions. When the rats were partially food-deprived every third day, cocaine infusions more than doubled during that session. When saline was substituted for cocaine, responding diminished over a 10-day period (Extinction Phase), but when the rats were subsequently food-deprived every third day (Testing Phase), for a total of six cycles (20 sessions), high rates of responding for saline were reinstated only during food deprivation sessions. Seven control groups were included to investigate several questions regarding this effect. Group C-1 received cocaine but no food deprivation experience during the Training Phase, and Group C-2 received food deprivation experience without cocaine access. The results showed that simultaneous presentation of both the food deprivation condition and cocaine was necessary to reinstate food deprivation-induced increases in responding during the Testing Phase. To test for the importance of the contingency between responding and cocaine infusions during food deprivation (and satiation) in the Training phase, Group C-3 was yoked to Group E; they received the same number and pattern of infusions during the Training Phase, but infusions were not contingent upon lever-press responses. This group showed only small increases in saline-maintained responding due to food deprivation during the Testing Phase. Groups C-4 and C-5 were treated as Groups C-3 and E, respectively, except they were partially food-deprived during the 10-day Extinction Phase. Three of five rats in Group C-4 and all rats in Group C-5 showed no increases due to food deprivation during the Testing Phase. Group C-6 was pre-exposed to food deprivation before the experiment began, and Group C-7 was exposed to food deprivation only once during the Training Phase. Both procedures weakened the ability of food deprivation to produce high rates of saline-maintained responding. It was concluded that novel interoceptive stimuli related to food deprivation had become associated with the relatively novel reinforcing effects of cocaine and these interoceptive stimuli functioned as conditioned reinforcers to increase the maintenance and reinstatement of drug-seeking behavior.