A vagally mediated histaminergic component of food-related drinking in the rat.

Six experiments with 95 male albino Sprague-Dawley rats (1) demonstrated that exogenous histamine was a potent stimulus for drinking behavior that was dependent upon an intact abdominal vagus and (2) provided evidence for a histaminergic component of the stimulus for food-related drinking in the rat. Histamine elicited drinking in a dose-related manner typically within 5 min after sc injection in Ss. Threshold for increased drinking was 1.25 mg/kg, and 2.5 mg/kg elicited half of the maximal drinking response that followed 20 mg/kg. Bilateral subdiaphragmatic vagotomy, with the hepatic branch left intact, severely attenuated drinking in response to systemic histamine: Vagotomized Ss drank later and less than did normal Ss after doses of histamine between 1.25 and 40 mg/kg. This attenuation was attributed to the destruction of vagal afferent fibers because histamine-elicited drinking was not affected by blockade of vagal efferents with atropine methyl nitrate. Drugs antagonistic to peripheral H? histamine receptors specifically inhibited drinking in response to histamine: Cimetidine or metiamide injected ip delayed and decreased drinking after sc histamine and temporarily decreased drinking after hypovolemia produced by sc polyethylene glycol, but failed to inhibit drinking after water deprivation, cellular dehydration, or isoproterenol. Finally, cimetidine or metiamide inhibited drinking in temporal association with a meal of liquid or solid food without slowing the rate of eating or decreasing food intake. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physiology of drinking elicited by eating.

Notes that much of normal drinking occurs around mealtime and that little is known about the physiological mechanisms involved, despite the identification of neurological substrates and physiological mechanisms for drinking in response to homeostatic deficit. The present author discusses the course of ingested food along the gastrointestinal tract, where food elicits a neuroendocrine cascade of events with the potential for mobilizing drinking. This perspective helps to identify histamine, and perhaps insulin and serotonin, as serving vagally mediated mechanisms that can elicit drinking around mealtime to preclude homeostatic imbalance. The experimental study of how normal drinking behavior ensures homeostasis by precluding homeostatic imbalance has the advantage of promising to enrich, rather than to damage, the status of homeostasis as a guiding principle for understanding the neurobiology of behavior. The concept would be enriched because it would become clear that cognitive functions such as learning, remembering, and planning one's behavior at times guarantee homeostasis and therefore prevent the necessity of a rapid behavioral response to repair the physiological emergency of a homeostatic deficit. (3? p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attack, eating, drinking, and gnawing elicited by electrical stimulation of rat mesencephalon and pons.

Conducted a study with 108 Long-Evans male rats. Eating, drinking, and gnawing were electrically elicited from the rat mesencephalon in the vicinity of the lateral branch of the descending medial forebrain bundle, but attack was evoked from the dorsomedial tegmentum adjacent to the central gray. The effective zones continued further caudally to the dorsal posterior pons. Unlike hypothalamically elicited behavior, eating, drinking, and gnawing often persisted 5-40 sec after termination of stimulation. Vocalization and escape activity were obtained principally from the vicinity of central pain pathways originating from the anterolateral cord. Other electrodes produced eating, drinking, gnawing, and grooming, which began only after termination of stimulation. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Histamine H3 receptors contribute to drinking elicited by eating in rats

A role for endogenous histamine and its H3 receptor subtype for mediating drinking elicited by eating was examined in adult male Sprague-Dawley rats. The i.p. injection of the H3 agonist R-alpha-methylhistamine (Ramh, 2.5 mg/kg) shortened the latency to initiate drinking and increased 1-h water intake in nondeprived rats freely eating pellets and drinking water. The ICV injection (through a surgically implanted chronic cannula) of 10 micrograms Ramh increased water intake; this Ramh-induced drinking was abolished by previous ICV injection of the H3 antagonist thioperamide (Th, 60 micrograms). For rats drinking and eating after 24-h food deprivation, s.c. Th inhibited drinking behavior: for example, 10 mg/kg Th s.c. delayed the latency to initiate drinking and inhibited 1-h water intake without inhibition of food intake. In contrast, 60 micrograms Th ICV failed to inhibit food-related drinking in rats eating after food deprivation. For nondeprived rats eating a small cracker, 10 mg/kg Th s.c. delayed the latency to initiate drinking and abolished water intake without effect of eating, and 60 micrograms Th ICV had similar effects upon drinking elicited by ingestion of cracker. The IG infusion (through a surgically implanted gastric catheter) of 2 ml 600 or 900 mOsm/kg NaCl, a treatment that is subthreshold for increase in systemic plasma osmolality at the initiation of drinking, elicited drinking that was abolished by 10 mg/kg Th s.c. and attenuated by 60 micrograms Th ICV. The IG infusion of 2 ml 1800 mOsm/kg NaCl, a treatment that is above threshold for increase in systemic plasma osmolality, elicited drinking that was attenuated by 10 mg/kg s.c. or 60 micrograms Th ICV. These results demonstrate that peripheral and central H3 receptors for histamine have a role in drinking elicited by eating and the postprandial gastrointestinal osmotic consequences of eating. These findings extend the evidence demonstrating a histaminergic contribution to food-related drinking in rats.     

Refractory periods of neurons directly excited in stimulus-bound eating and drinking in the rat.

Studied male hooded rats to determine whether the amygdaloid, or the brainstem, or neither population of neurons is involved in eating and drinking. Latency to the onset of eating or drinking became short when the intrapair interval of twice-threshold stimulating pulse pairs was increased beyond .50-.65 msec. This indicates that the absolute refractory periods of neurons directly excited in eating and in drinking elicited by lateral hypothalamic stimulation are between .50-.70 msec. The previous finding that the absolute refractory period characteristic of basolateral amygdaloid neurons directly excited by the same lateral hypothalamic stimulation is also in this range is considered evidence that the amygdaloid neurons are involved in the eating and drinking. Results also indicate either that the eating and drinking are elicited through different neurons with similar characteristics, or through the same neurons. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of drinking history on food-deprived drinking in the rat.

Investigated the role of drinking during development in 40 male hooded Long-Evans rats. Experimental Ss were deprived of water during rearing; ingestion of lettuce provided for sufficient fluids. Body weight, feeding, drinking, and urine volume over successive food deprivation periods were compared with normally reared controls. The lettuce-reared Ss drank less water and ate less lettuce when food deprived, but did not differ from normal Ss in drinking or in lettuce intake when food was available ad lib. It is suggested that lettuce-reared animals drink water principally in response to fluid deficits. Other research indicates that the drinking of normally reared rats anticipates fluid deficits and is not initiated by events related to the need for water. The present results suggest that this anticipatory drinking is acquired. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Facilitation and suppression of centrally elicited feeding and drinking by electrical stimulation of the midbrain.

Stimulated the lateral hypothalamus of 25 male Wistar rats to elicit feeding and drinking responses. A pulse of stimulation was then presented to the midbrain reticular formation 10 or 16 msec after each pulse to the lateral hypothalamus (dual stimulation). When the interval between pulses was 16 msec, elicited feeding and drinking were significantly reduced during dual stimulation. When the interval was 10 msec, the elicited responses were facilitated in some cases and inhibited in others. Results are interpreted as tentative support for the view that the lateral hypothalamus and midbrain interact in the control of ingestive behaviors, but the site of this interaction has not been determined. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of amygdaloid lesions on eating elicited by cortical spreading depression

The investigations were carried out in 296 patients with myocardial infarction (238 men and 58 women) aged 24-91 years, admitted to an intensive care unit on the 1st or 2nd day of the disease. In all patients the catheter for determination of central venous pressure was introduced into the right atrium through the cephalic vein the the first 100 cases, and through the subclavian vein in 196 cases. The catheter was kept in the atrium for 3-4 days. Values of c.v.p. between 50 and 120 mm Hg were accepted as normal.     

Periprandial self-intravenous drinking in the rat.

Describes 4 experiments in which self-injected intravenous (iv) drinking (SID) of intact and desalivated male albino Wistar rats (N = 29) was studied over long periods in relationship with continuously recorded feeding of powdered chow. Periprandial episodes of SID were similar to those of oral drinkers, but the preprandial anticipatory component was increased in these permanently dehydrated (oliguric) Ss. The elimination of hedonic factors together with the observed responses to calorically or osmotically modified diets available ad lib or in restricted schedules (1 or 2 meals a day) emphasized the regulatory role of periprandial drinking. Ss that received injections in parallel with their SID-paired partners showed a nonreliable meal onset following iv water receipt; generally, meals remained taken in an idiosyncratic pattern. In the absence of food, SID Ss continued the rhythm of iv water ingestion. Results are discussed with reference to regulatory nature of drinking and to biological oscillator models. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hypothalamic knife cuts: Effects on eating, drinking, irritability, aggression, and copulation in the male rat.

Describes 2 experiments with a total of 43 male hooded rats. In Exp. I, Ss with parasagittal knife cuts that separated the medial from the lateral hypothalamic areas (a) became hyperphagic, hyperdipsic, obese, and irritable; (b) did not change their level of aggressive responses against mice; and (c) copulated at an impaired rate or not at all. In Exp. II, 2 groups of Ss were subjected to coronal cuts restricted between the fornices at levels either anterior or posterior to the ventromedial hypothalamic nuclei. Most of the anterior-cut Ss increased their food and water intake, and some became irritable. Of the posterior-cut Ss, none increased and 1/2 decreased their food intake, some became hyperdipsic, and 1 became irritable. Neither of the coronal-cut groups changed levels of aggressive or sexual responses. It is concluded that the mediolateral hypothalamic connections are important for eating, irritability, and copulation. (42 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Female lordotic behavior mediated by monoamines in male rat.

In Exp I direct application of serotonergic or b-adrenergic receptor blockers to anterior or posterior areas of the hypothalamus induced lordosis in 18 intact estrogen-primed male Sprague-Dawley rats. Such treatment with an a-adrenergic blocker or systemic administration of progesterone failed to increase lordosis. In Exp II (n = 7) centrally elicited lordosis did not occur without estrogen priming. It is concluded that anatomical and neurochemical similarity may exist in the brain mechanism mediating lordotic behavior in male and female adult rats. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Forebrain lesions differentially affect drinking elicited by dipsogenic challenges and injections of muscimol into the median raphe nucleus.

Injections of muscimol into the median raphe nucleus (MR) elicit intense drinking in normally hydrated rats. To determine whether this response is dependent on forebrain systems mediating other aspects of water intake, the authors examined the effects of lesions of the subfornical organ (SFO), median preoptic nucleus (MnPO), lateral preoptic area (LPO), or lateral hypothalamus (LH) on the drinking. Lesions of the SFO or LH attenuated muscimol-elicited drinking, whereas lesions of the MnPO or LPO increased water intake after the treatment. All of the lesion groups showed a deficit in drinking to injections of polyethylene glycol and at least one of the doses of hypertonic saline. Only the SFO- and LH-lesioned groups showed a suppression of drinking to systemic injections of angiotensin II, suggesting that the drinking elicited by intra-MR injections of muscimol may involve changes in the central circuits mediating angiotensin-induced drinking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Abdominal vagotomy disrupts food-related drinking in the rat.

In 2 experiments with a total of 41 Sprague-Dawley albino rats, Ss with complete subdiaphragmatic bilateral transection of the abdominal vagus (Vgx-C) showed disordered food-related drinking when drinking water in temporal association with a meal of dry food after 5-hr food deprivation and when drinking water in association with a liquid meal after 24-hr food deprivation. The Vgx-C Ss drank after significantly longer latencies and drank significantly less water in 1 hr than did sham-vagotomized (Sham) Ss after eating the same size meal (solid or liquid). Ss with incomplete vagal transection (Vgx-I) ate and drank like Shams. Water intake of Sham and Vgx-I Ss correlated positively with the meal size of solid food, but the water intake of Vgx-C Ss did not. The failure of Vgx-C Ss to drink water normally when food was ingested was not due to failure of a food stimulus to reach the intestine, because Vgx-C and Sham Ss emptied equivalent volumes of liquid food from the stomach into the intestine within 10 min of food entering the stomach. Results indicate that the abdominal vagus is an important neurological substrate for food-related drinking in the rat. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Long-term self-intravenous "drinking" in the rat.

Results of a series of experiments show that male Wistar albino rats, when water was available only by intravenous self-injection, learned to rehydrate by pressing a lever even after desalivation and for periods up to 90 days. It appears that hydromineral regulation was occurring about a new, lower set point for body fluid content which was necessary for the onset and maintenance of intravenous "drinking." The regulatory nature of the operant was confirmed by appropriate modulation of operant rate to amount of reinforcement per leverpress and in tonicity of self-injected fluid. There seemed to be some "motivational deficits," and these Ss did not respond for intravenous water as the oral controls did when challenged with traditional intra- and extracellular thirst stimuli. More complex stimuli (e.g., heat and salty food) led to compensatory responding. While interoceptors alone seemed capable of eliciting the defense of a homeostatic hydromineral balance, the control over the operant was less precise than for normal oral drinking. (57 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differences in affiliative behavior of weanling rats selecting eating and drinking sites.

In 3 experiments with Long-Evans rats, the presence of an adult at a feeding site profoundly influenced a conspecific weanling's probability of eating there. Presence of an adult at a drinking site did not have a comparable effect. This indicates that the influence of adult presence at a feeding site on pup feeding site selection, reported in previous studies, is not simply an epiphenomenon reflecting a general affiliative tendency of rat pups. Rather, social affiliation appears to be a factor of special importance in the feeding site selection of young rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Water-intake volume regulation in the rat: Schedule-induced drinking compared with water-deprivation-induced drinking.

Hungry rats drink extremely large amounts of water when they are intermittently fed small amounts of food (schedule-induced polydipsia). The present 5 experiments examined whether such animals are motivated to drink for long durations, to ingest large amounts of fluid, or to do both. When drinking-tube apertures were decreased to slow the rate of water ingestion, each of 8 female Sprague-Dawley rats spent more time drinking than when larger apertures were used (averages of 11.5 vs 7.8 min, respectively). The mean volumes ingested were not different. These equal volumes were generated by adjustment of each drink duration in accordance with ingestion rate even during the first few drinks of the sessions and when the drinking tubes were frequently switched (every 1–3 min) during the sessions. During drinking induced by water deprivation when food was concurrently available, restriction of the tube apertures reduced intake volumes by 18–29%. However, when food was not concurrently available during water-deprivation-induced drinking, regulation of intake volumes was comparable with that found during schedule-induced polydipsia. Data pose difficulties for theories that ascribe a crucial role to the motor aspects of schedule-induced drinking. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral and pharmacological specificity of the feeding elicited by cholinergic stimulation of the substantia nigra in the rat.

In 4 experiments, microinjections of the cholinergic agonist carbachol into anterior substantia nigra dose dependently increased food intake in satiated rats (31 male Listar hooded rats and 13 hooded PVG/C rats). This resulted from a prolongation of the duration of eating. In the absence of food, those doses of carbachol that stimulated food intake (.1 and .5 μg) had no effect on any other response examined, including gnawing, drinking, locomotion, grooming, sniffing, and rearing. The effect of carbachol depended on the degree of prior food deprivation, but supra-additive effects of carbachol and deprivation were not observed. These results are contrasted with those of previous studies demonstrating the nonspecific behavioral effects of electrical stimulation of the brain and of studies showing that carbachol has radically different behavioral effects at other CNS sites. Microinjection of an acetylcholine/eserine sulfate mixture also significantly increased food intake. This response was abolished by prior microinjection of the muscarinic receptor antagonist atropine into the substantia nigra, a result that provides evidence for pharmacological specificity of the behavioral effects. Data provide further evidence for the hypothesis that a functional cholinergic system is present within substantia nigra. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Abdominal vagotomy inhibits osmotically induced drinking in the rat.

Results of a study with 35 male Sprague-Dawley rats show that after complete bilateral transection of the abdominal vagus (Vgx-C9), with the hepatic branch left intact, Ss drank later and less than normal after cellular dehydration induced by hypertonic saline. When access to water was delayed for 1 hr after cellular dehydration, Vgx-C Ss initiated drinking quickly with normal latency, but (a) a gastric water preload was a more effective stimulus for drinking suppression in Vgx-C than in normal Ss; (b) gastric emptying of a water or phenol red solution preload was more rapid in Vgx-C than in normal Ss; and (c) when gastric emptying dysfunction in Vgx-C Ss was removed by having Ss sham drink, Vgx-C and normal Ss sham drank equivalent amounts of water. Thus, disordered preabsorptive satiety caused by abnormally rapid gastric emptying of water was a factor in the decreased drinking of Vgx-C rats after cellular dehydration. Disordered satiety for ingested water could not, however, account for the abnormal latency to initiate drinking after cellular dehydration in Vgx-C rats. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of nitric oxide and vasoactive intestinal polypeptide in vagally mediated relaxation of the gastric corpus in the anaesthetized ferret

We have examined the role of protein kinase C (PKC) in the stimulation of protein synthesis by insulin using two complementary approaches. In the first, fibroblasts were pretreated with phorbol esters to down-regulate PKC. In these cells, the effects of insulin and of phorbol esters on protein synthesis were completely abolished, although serum still elicited an effect approaching that seen in control cells. Secondly, we used newly developed inhibitors of PKC which, again, blocked the effects of insulin and phorbol esters without greatly reducing the response to serum. Thus PKC apparently plays an important role in the stimulation of translation by insulin.     

A purinergic component of the excitatory postsynaptic current mediated by P2X receptors in the CA1 neurons of the rat hippocampus

The pyramidal neurons in the CA1 area of hippocampal slices from 17- to 19-day-old rats have been investigated by means of patch clamp. Excitatory postsynaptic currents (EPSCs) were elicited by stimulating the Schaffer collateral at a frequency below 0.2 Hz. It was found that inhibition of glutamatergic transmission by 20 microM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 100 microM 2-amino-5-phosphonovaleric acid (D-APV) left a small component of the EPSC uninhibited. The amplitude of this residual EPSC (rEPSC) comprised 25 +/- 11% of the total EPSC when measured at a holding potential of -50 mV. The rEPSC was blocked by selective P2 blocker pyridoxal phosphate-6-azophenyl-2'-4'-disulphonic acid (PPADS) 10 microM and bath incubation with non-hydrolysable ATP analogues, ATP-gamma-S and alpha, beta-methylene-ATP at 50 and 20 microM, respectively. The rEPSC was dramatically potentiated by external Zn2+ (10 microM). In another series of experiments exogenous ATP was applied to the CA1 neurons in situ. An inward current evoked by ATP was inhibited by PPADS to the same extent as the rEPSC. It is concluded that, depending on membrane voltage, about one-fifth to one-quarter of the EPSC generated by the excitatory synaptic input to the hippocampal CA1 neurons of rat is due to the activity of P2X receptors.