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D G Mook

Publications and source records attributed to D G Mook.

At least 37 records · Page 2Linked to original sources
PubMed1987

Some determinants of the time course of saccharin ingestion in hungry rats.

In rats that are food- but not water-deprived, a saccharin "meal" is characterized by a progressive decrease in lap rate as the bout progresses. However, saccharin does not trigger a fixed rate of lapping at any point in the sequence. When rats have only intermittent access to saccharin early in the session, they increase their rates of lapping so that, within each few minutes, the amount of lapping (or some correlate such as volume drunk) is held constant. This happens over a wide range of restriction conditions. And if compensation cannot occur during a period of constraint, then it occurs afterward, promptly and precisely. When constraint is withdrawn, rats drink amounts such that the total amount of drinking (or its correlate), through that point in the ingestive bout, is defended. These findings imply that the controlling system includes (1) an integrator that keeps track of the amount of drinking that has occurred, even across interruptions; and (2) a short-term feedback loop that operates minute by minute within the bout. This loop regulates, not the rate of lapping to be emitted, but the amount of lapping to be done (or its correlate); Thus the decline in responsiveness to saccharin as drinking progresses reflects a depression of this regulated value, not of lap rate per se.

Animals↗
PubMed1986

Satieties and cross-satieties for three diets in the rat.

In food-deprived rats, intake of a 2 M glucose solution is independent of deprivation level. However, subsequent intake of laboratory chow does vary with deprivation, though the immediately-preceding glucose meal did not. If deprivation is severe, the rat may eat as much chow as if the prior glucose meal had not occurred. In the converse case, a preload of chow has no suppressant effect whatever on intake of glucose, at any deprivation level. As with chow, intake of milk after a glucose load varies with food deprivation, even though the preceding intake of glucose did not. In contrast to the chow case, however, there is cross-satiety between milk and glucose in both directions; a meal of either one suppresses subsequent intake of the other. We conclude: (1) Intake of different diets is limited (satiated) by different postingestive mechanisms with different functional properties; some are sensitive to deprivation, others not. (2) Offering a new diet can change the properties of satiety, as if it recruited a new satiety mechanism and disengaged the old one. (3) The interactions among different satiety mechanisms are complex and non-reciprocal. Glucose and milk both contribute to a satiety mechanism that limits intake of both. A glucose preload can augment or accelerate satiety for chow, and thus reduce chow meal size; but the converse is not true. A single state or variable, "satiety" in the abstract, probably does not exist.

Animal Feed↗
PubMed1986

Satiety for glucose solution in rat: the specificity is postingestive.

Rats that have drunk a concentrated glucose solution to satiety, and will drink no more of it if access is prolonged, will return to vigorous ingestion if offered carbohydrate powder or laboratory chow. We show that this specificity of satiety is maintained even if the initial glucose load is delivered directly to the stomach, bypassing the stimuli and the responses associated with spontaneous ingestion. Therefore, the specificity of satiety for glucose does not reflect sensory- or response-specific satiety.

Animal Feed↗
PubMed1986

Saccharin drinking by hungry rats: adjustment to constraints.

In food-deprived rats, rate of lapping at a saccharin cylinder declines progressively over a session. The decline is unaffected, within limits, by restricted access: Whether the cylinder is available continuously, or only during alternate 30-sec intervals, the rat adjusts its momentary lap rate so that the amount of lapping within each 5-min period remains the same. It is as if the rat specifies over each brief period how much ingestive behavior is to occur, and then adjusts its lap rate so that actual ingestive behavior matches the specification. The specification in turn moves down as the drinking bout progresses.

Animals↗
PubMed1984

Behavioral correlates of oral and postingestive satiety in the rat.

Hungry rats display the characteristic "satiety sequence" after drinking a glucose solution: The end of ingestion is accompanied by grooming and exploring, followed by resting. With saccharin solutions over a range of concentrations, however, ingestion is accompanied and followed by persistent grooming and exploring; resting rarely occurs. Gastric preloads of glucose solution promote resting to reinstate the "satiety sequence" after a bout of saccharin ingestion. Therefore, the systemic effects of glucose are sufficient to promote resting. In the absence of postingestive factors, the "satiety sequence" is incomplete following saccharin ingestion as it is after sham-feeding.

Animals↗
PubMed1984

"De-satiation" produced by liquid diet in rats satiated for glucose solution.

Previous work has shown that after rats have drunk a glucose solution to "satiety," and during the time when solution intake would remain inhibited, intake can be reinstated by offering powdered glucose. This "de-satiation" phenomenon shows that solution intake comes to an end before any limit on caloric or solute intake has been reached. Here we show that a milk-based liquid diet can also reinstate ingestion in the solution-sated rat. And such a rat increases its intake further when the diet is diluted with water. Therefore, the original "satiety" for glucose solution does not reflect a refusal of fluid per se, or of water; nor does it reflect an inhibition on the lapping response.

Animals↗
PubMed1983

"De-satiation": the reinstatement of feeding in glucose-satiated rats.

In rats "satiated" for glucose in solution, feeding can be reinstated by presentation of the same commodity (glucose) in powdered form. The effect is not reciprocal, so it is not a response to change or variety per se; and it does not reflect a greater palatability of the powder, which is rejected in favor of the solution in choice tests. Sucrose powder leads to an even larger "second meal" than glucose powder, showing that intake in the solution-sated rat remains sensitive to the stimulus properties of the diet. We conclude that the postingestive conditions necessary for satiety must be set by the stimulus properties of the diet--including, but not limited to, the properties that specify a diet's nutrient composition.

Animals↗
PubMed1983

Effects of food deprivation on intake of solid and liquid sugars in the rat.

In free-feeding rats, glucose at 0.025 M or 2 M evokes a vigorous bout of drinking. Powdered sucrose evokes more feeding than would occur without it, but powdered glucose does not. Food deprivation has little effect on intake of 2 M glucose, but it markedly augments intake of the powders, which rises to caloric-intake values higher than that of the 2 M solution. This occurs even if the powders are offered only after solution intake has come to an end and at a time when it would remain inhibited. We conclude: 1. Some sweet-tasting commodities will evoke ingestive behavior in free-feeding rats, but others, some of them even sweeter, will not. 2. Solid carbohydrates follow different laws from concentrated carbohydrate solutions, in that the former, but not the latter, rise with deprivation. Intake of powders must therefore be limited or satiated by different and more permissive mechanisms from the ones that limit solution intake.

Animals↗
PubMed1983

Glucose solution intake in the rat: the specificity of postingestive satiety.

Hungry rats were permitted to drink a concentrated glucose solution to 'satiety', as indicated by (1) cessation of drinking, (2) the appearance of behaviors correlated with satiety (grooming and exploring followed by resting), and (3) refusal to drink appreciable further quantities when access to the solution was prolonged. Yet such rats returned to vigorous and prolonged feeding when offered laboratory pellets, powered chow, or even glucose itself in powered form. "Satiety" for a glucose solution does not reflect a generalized suppression of hunger or of a specific carbohydrate hunger. Its properties are more specific than existing theories of energy intake regulation would lead us to suppose.

Animals↗
PubMed1983

Oropharyngeal control of ingestion in rats: acquisition of sham-drinking patterns.

Rats with esophageal fistulas, offered a concentrated glucose solution, sham drank relatively small amounts on the first session. This was true whether or not such a solution was familiar. Intake rose to very high levels over ensuing sham-drinking sessions, a result showing that the initial small volumes were not attributable to fixed properties of the solution itself (e.g., aversiveness, viscosity, or input to "satiety" mechanisms). The gradual acquisition of copious sham drinking was not affected by previous "practice" at sham drinking other commodities; it was not simply an alteration in motor habits. Finally, the gradual acquisition of the sham-drinking pattern did not occur with more dilute solutions; in response to these, sham drinking was copious and continuous from the outset. The following conclusions are made: (a) Rats must learn to respond, by continuous drinking, to the absence of the postingestive inhibition normally produced by concentrated solutions. (It is a separate and open question whether the response to the presence of such inhibitory factors must also be learned.) (b) No such learning is required in the case of more dilute solutions. This is further evidence that controlling factors with differing properties operate at different levels even of the single commodity, glucose in solution.

Animals↗
PubMed1983

The state of the art and the fate of the earth.

A recent review by Nevin of Jonathan Schell's The Fate of the Earth applies a "behavioral perspective" to the problem of species survival in a nuclear age. It is suggested that no perspective, in this context as in others where less is at stake, should dismiss prematurely some useful ideas from other perspectives. A sampling of "cognitive" concepts is offered to illustrate what actions, aimed at resisting species extinction, might follow from them-not instead of, but in addition to, the guidelines for action a behavioral perspective provides.

Journal Article↗
PubMed1975

Some observations on the preference deficits produced by lateral preoptic lesions in the rat.

Following water drprivation, rats with lateral preoptic (LPO) damage lose the normal preference for glucose solutions. Food deprivation reinstates the preference. This dependency is specific to sweet-tasting fluids, and the deficit persists even if thirst is alleviated prior to the preference test. Such rats will drink sweet solutions in response to intravascular fluid depletion, but they are deficient in response to sweet solutions under nondeprived conditions. This last finding in particular suggests that hunger and palatability, as determinants of the response to sweet solutions, may be dissociated by LPO damage.

Animals↗