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D G Mook

Publications and source records attributed to D G Mook.

At least 19 recordsLinked to original sources
PubMed1992

Effect of body weight manipulations on sham feeding in the rat.

Rats with chronic esophageal fistulas were permitted to sham-feed a carbohydrate solution (a simplified model food) for a 40-min session each day. Body weight was elevated, then reduced again, by varying the caloric density of the liquid diet by which the rats were maintained. With 1M glucose as tastant, induction of mild obesity caused an abrupt reduction in sham meal size. Sucrose concentration-intake functions were lowered at all concentrations by mild obesity, but without change in slope. Both changes were reversed by weight reduction to around normal body weight; further weight reduction produced no further change. Therefore, some correlate of body weight biases the oral control of bout size. The bias seems to change rather abruptly between one value and another at a weight level slightly above normal.

Animals↗
PubMed1992

How important is hedonism? Reasons given by college students for ending a meal.

College students (N = 64, 50, and 36 in three replications) were asked to complete the statement, "I usually stop eating a meal when ...". A number of alternatives were offered, together with an open (write-in) option. By far the most common completion was "... I feel full". The hedonic alternatives, "... the food stops tasting good" (first study) or "the food tastes less good" (first replication) were chosen by very few of the subjects, though explicitly presented as alternatives. In a second replication, subjects rank-ordered in importance the various reasons for ending a meal; not all subjects ranked the hedonic alternative at all, and most of those who did ranked it low in importance. Though hedonic shifts during a meal have been repeatedly shown to occur, these data suggest that they are of little salience, and perhaps of little importance, as factors in meal termination.

Adult↗
PubMed1991

Preparation and maintenance of chronic esophagostomized rats: an update.

We report significant improvements in our procedures for preparing and maintaining rats with esophageal fistulas and gastric cannulas. The most important of these are 1) a new cannula assembly, 2) a two-stage surgical procedure, 3) a modified diet, and 4) a less stringent maintenance regimen.

Animals↗
PubMed1991

All-or-none suppression of glucose sham feeding by an intragastric mixed meal in rats.

Rats were permitted to sham feed a 1 M glucose solution after varying delays (0-40 min) following the intragastric (IG) infusion of a large, nutritionally adequate meal. (a) The meal affected sham feeding in an all-or-none way. After such a meal, sham feeding was either suppressed almost entirely, or it was not suppressed at all as compared with a no-meal control condition. (b) When it occurred, the suppression was short-lived: As little as a 20-min delay after the meal could suffice to change its suppressant effect from "all" to "none." This implies in turn that the much longer suppression found under other conditions is not a product of systemic inhibition on readiness to ingest. (c) The duration of the suppression appeared to decrease with successive exposures to the experimental conditions. After several such exposures, some rats showed no postprandial suppression at all, even immediately after the IG meal.

Animals↗
PubMed1990

Functional recovery of the gustatory system after sodium deprivation during development: how much sodium and where.

Restriction of maternal dietary sodium beginning on or before embryonic day 8 and continued thereafter results in reduced taste responses of the chorda tympani nerve to NaCl in the offspring. The effects of deprivation, however, are reversible. A single ingestive bout of 30 ml isotonic NaCl was sufficient to restore normal sodium taste, and the restorative effects of the single exposure apparently persisted throughout multiple generations of taste receptor cells. Furthermore, the recovery apparently did not depend on direct receptor cell-stimulus interactions. Rats permitted to drink 30 ml of isotonic NaCl, but not allowed to retain it, did not recover normal sodium taste responses, suggesting that factors other than taste stimulation are important in the restorative effects of sodium.

Amiloride↗
PubMed1989

Adjustment to intermittent access in rats drinking saccharin: II. Adjustment of lapping rate.

Hungary rats were permitted to drink saccharin under conditions in which (a) the drinking spout was available continuously, or (b) it was withdrawn during alternate 30-sec periods. Rats adjust to such constraint by increasing their integrated lap rate (laps/min). We show that one way in which they do this is to lap at a higher rate within bursts of lapping. This faster lapping is not an artifact of forced interruptions and resumptions. It cannot only be maintained over a drinking session, but also initiated midway through the session if restricted access is imposed then. Therefore, the period of the lapping cycle can be adjusted, within limits, in response to situational constraints on access to the fluid.

Animals↗
PubMed1989

Orosensory suppression of saccharin drinking in rat: the response, not the taste.

Hungry rats drink saccharin solutions with avidity, but the ingestion is self-limited: rate of lapping slows down progressively. Since postingestive changes do not produce this suppression, it must depend on a feedback signal generated by lapping the fluid. We show that the suppression depends on the number of laps emitted, not on the taste of the fluid; a given number of laps early in the session produces the same suppression later in the session, whether those early laps are accompanied by a moderate saccharin taste, a weak taste, or no sweet taste at all. Therefore, the feedback signal is provided by the act of lapping; taste does not contribute to it. Yet taste does influence amount ingested. Perhaps it provides a feed-forward signal, that in turn sets the amount of feedback required to end the bout.

Animals↗
PubMed1988

Adjustment to intermittent access in rats drinking saccharin: I. Pauses in drinking.

Hungry rats drink saccharin solutions avidly. When access to the cylinder is restricted, so that it is available during alternate 30-sec periods rather than continuously, rats adjust to this constraint so that total amount of lapping, over each period of a few minutes each, is defended. We show that the rats achieve this defense, in part, by pausing less often and for briefer periods between bursts. Log-survivorship analysis of the pauses in drinking suggests (a) that they are generated by two processes with different time constants, (b) that early in the session, both processes are suppressed when access is restricted; and (c) that later in the session, pauses reflecting the shorter-term process begin to appear, even if access is restricted. Therefore, adjustment to constraints on access is achieved in part by suppression or inhibition of two processes that generate pauses, and the suppression is relaxed earlier for the one with shorter time constant.

Animals↗
PubMed1988

Sham drinking of glucose solutions in rats: some effects of hydration.

Sham-drinking patterns were observed in rats with oesophageal fistulae and gastric cannulae. In rats both food- and water-deprived at test, first-session sham intake was an inverted U-shaped function of glucose concentration (the preference-aversion pattern). Sham intake at low and high extremes rose with repeated exposure, so that the function flattened. When the rats were hydrated by a gastric water preload, sham intake of glucose at low concentrations was much reduced, whereas sham intake at high concentrations was little affected, so that the function became monotonic increasing. This time sham intake rose with repeated testing at high concentrations, but not low ones, so that the function steepenned. At low concentrations, the low sham intakes reflected a rapid termination of the sham-drinking bout. This does not reflect a delayed effect of the gastric water load, for introducing a further delay between load and drinking test did not enhance the effect. Finally, an intragastric load of isotonic NaCl was less effective than water in suppressing sham drinking, just as it is less effective in inhibiting thirst. We conclude: (1) sham drinking is terminated by an accumulation of orosensory feedback; and (2) the taste presented to the mouth, and the animal's hydrational status, jointly determine the amount of such feedback that is necessary to end the ingestive bout.

Animals↗
PubMed1988

Glucose sham drinking in the rat: satiety for the sweet taste without the sweet taste.

In rats sham drinking through oesophageal fistulae, sham intake of a dilute glucose solution (0.25 M) is greatly reduced, but not abolished, by an intragastric water preload. Since no further fluid enters the body, the early cessation of sham drinking must reflect a purely oral control, set by hydrational status. We show that lapping after the water load is abolished if the rat has sham-drunk appreciable quantities before the load is delivered. This is true even if the initial sham drinking is of plain water, with no sweet taste. Therefore, (1) the effect of the preload is to set the total quantity of oral feedback required to end the sham drinking bout; and (2) the necessary oral feedback is provided by the lapping response itself. It does not depend upon gustation.

Animals↗
PubMed1987

Preparation and maintenance of rats with chronic esophagostomy and gastric cannula.

We describe surgical and maintenance procedures for the "double-fistula" preparation in rat. Rats are prepared with esophageal fistulas, so that material swallowed escapes from an opening in the throat; and with gastric cannulas that permit both nutritional and hydrational maintenance, and the experimental intubation of fluids directly into the stomach.

Animals↗
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↗