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At least 541 records · Page 30Linked to original sources
PubMed1994

Effects of the neuroleptic alpha-flupenthixol on latent inhibition in aversively- and appetitively-motivated paradigms: evidence for dopamine-reinforcer interactions.

Three experiments examined the influence of the dopamine (DA) D1/D2 receptor antagonist alpha-flupenthixol on the latent inhibition (LI) effect. LI is a phenomenon which is manifest when non-reinforced pre-exposure to a stimulus retards subsequent conditioning to that stimulus, and has been proposed as an animal model of the selective attentional processes that are disrupted in acute schizophrenia. Experiment 1 extended previous findings that neuroleptics enhance the LI effect in conditioned suppression paradigms in rats to alpha-flupenthixol (0.23 mg/kg). Experiment 2 demonstrated that this enhancement of the LI effect was also seen in a parallel appetitively-motivated conditioning paradigm at the same dose. In both Experiment 1 and Experiment 2, the enhancement of the LI effect by alpha-flupenthixol appeared to be accompanied by a decrease in the impact of the reinforcer (be it appetitive or aversive). Experiment 3 investigated the possible role of the reinforcer in the effect of alpha-flupenthixol on the LI effect in the aversive, conditioned suppression paradigm by increasing the intensity of footshock in rats treated with alpha-flupenthixol. Increasing the intensity of the footshock completely abolished the enhancement of LI found following injection of alpha-flupenthixol, a result which could not be attributed to a floor effect. The results provide no support for interpretations of the influence of DA manipulations on the LI effect that draw parallels with deficits in selective attention observed in acute schizophrenia.

Acoustic Stimulation↗
PubMedDate not supplied

Pavlov and appetite.

Before working on conditioned reflexes, Pavlov completed a research program designed to investigate the physiological controls of salivary, gastric, and pancreatic secretions. The originality and significance of this work resulted in a Nobel Prize in 1904, the first awarded to a physiologist. The first part of this manuscript focuses on the experimental analysis of the controls of gastric secretion. This demonstrates Pavlov's experimental skill and his ability to draw strong inferences about how a psychic factor like appetite grew into a physiological effect, such as gastric secretion. The second part of the manuscript reviews Pavlov's ideas about the central neural mechanism for appetite and its stimulatory effect on gastric secretion, and demonstrates that Pavlov's "conceptual nervous system" is very similar to our own.

Animals↗
PubMedDate not supplied

Acquisition and discrimination of appetitively and aversively conditioned heart rate responses in rhesus monkeys.

This report describes the acquisition of a conditional heart rate response to both classical aversive and appetitive conditioning in eight rhesus monkeys (Macaca mulatta). The behavioral paradigm consisted of two discrete one minute tones followed by the corresponding unconditional stimuli, i.e., electric shock or Purina monkey chow. A third tone followed by neither food nor shock served as a discriminative stimulus (DS). The conditional heart rate responses developed in two phases. The first phase was characterized by similar responses to both conditional stimuli and the DS. Control heart rate rose during this period. During the second phase, control heart rate decreased (five animals), the DS response disappeared, and different conditional heart rate patterns to food and shock emerged. The existence of distinct conditional response patterns indicates probable differences in the autonomic nervous regulation of the heart during aversive and appetitive conditioning.

Animals↗
PubMed2000

Appetitive nature of drug cues confirmed with physiological measures in a model using pictures of smoking.

RATIONALE: In smokers, pictures of smoking that increase desire for a cigarette are described as pleasant rather than unpleasant. This suggests that these smoking cues may be appetitive and not withdrawal-like or aversive as held by traditional theories of drug cue formation. OBJECTIVE: Cues for smoking were examined using physiological measures of motivational valence. METHODS: Non-deprived smokers, deprived smokers and deprived smokers who expected to smoke (n=54) viewed a computer screen presenting experimental and control scenes (experiment 1). The acoustic startle reaction and activity of the corrugator and the zygomatic facial muscles were then measured after onset of smoking cues and standardized pleasant, neutral or unpleasant control scenes. Individuals who never smoked (n=18) were also used to test for cue effects on startle (experiment 2). RESULTS: No evidence was found that smoking cues were aversive in smokers. The smoking cues affected the startle responses and corrugator activity in a way similar to that of pleasant control material but significantly different from that of unpleasant material; the cue effects on zygomatic activity was most similar to that of neutral material. The general pattern of effects was not influenced by overnight smoke deprivation, expectancy to smoke or smoke repletion, but it was different in never smokers where the smoking scenes were found to be similar to unpleasant control scenes. CONCLUSIONS: Nonsubjective measures of motivational valence further suggest that drug cues are conditioned stimuli having appetitive effects. Startle response modulated by drug cues may be useful for probing motivational processes underlying dependence in the human.

Adult↗
PubMed1997

5-HT2C receptor activation decreases appetite and body weight in obese subjects.

We studied the effect of 2 weeks administration of the 5-HT2C receptor agonist, m-chlorophenylpiperazine (mCPP), on appetite and body weight in 18 moderately obese subjects in a double-blind, placebo-controlled trial, mCPP caused a small but significant (0.75 kg) reduction in body weight and in subjective ratings of hunger. Plasma prolactin was significantly elevated by the final dose of mCPP. Our data suggest that during 2 weeks treatment in humans, mCPP may continue to activate brain 5-HT2C receptors, and that this effect is associated with decreases in appetite and body weight.

Adult↗
PubMed2006

Facilitated extinction of appetitive instrumental conditioning following excitotoxic lesions of the core or the medial shell subregion of the nucleus accumbens in rats.

The nucleus accumbens has been implicated in the control of goal-directed behaviour, including instrumental conditioning. Here, we evaluated the effect of N-methyl-D: -aspartate (NMDA)-induced excitotoxic lesions restricted to either the core or the medial shell subregions of the nucleus accumbens (NAC) on extinction in rats using a trial discrete fixed ratio-5 (FR-5) appetitive operant procedure. Neither core nor shell lesions of the NAC affected the acquisition of instrumental responding. Both lesions facilitated the cessation of responding when the instrumental act no longer yielded reinforcement. Our results suggest that both the NAC core and medial shell contribute to the control of extinction learning of appetitively motivated instrumental behaviour.

Analysis of Variance↗
PubMed2003

The effect of temperature on digestive and assimilation efficiency, gut passage time and appetite in an ambush foraging lizard, Cordylus melanotus melanotus.

In ectotherms, an increase in body temperature increases metabolic rate and may increase rates of digestive processes. We measured the thermal dependence of the apparent digestive and apparent assimilation efficiencies (ADE and AAE), gut passage time (GP) and appetite in Cordylus melanotus melanotus, a medium sized Crag Lizard, which is endemic to South Africa. Trials were conducted at 20, 22, 25, 30, 32 and 35 degrees C under controlled conditions. Trials lasted 14 days, during which, lizards were fed ca. 1 g mealworms per day. Glass beads were used as markers to determine GP at the beginning and end of trials. Faeces and urates were collected daily and oven dried at 50 degrees C. The energy content of egested matter was then measured using bomb calorimetry. ADE and AAE were not affected by temperature for either males or females. The mean+/-SE ADE and AAE were 94.4+/-0.3% and 87.2+/-0.6%, respectively. GP was not significantly different between males and females at any temperature, but decreased significantly with increasing temperature. Appetite was significantly different between the different temperatures measured. The decrease of gut passage time with increasing temperature was expected, since the digestive and assimilation efficiencies are similar over the range of temperatures tested. Lizards are thus assimilating a similar proportion of ingested energy, but at faster rates at higher temperatures. The results indicate that the digestive physiology of this species results in maximum energy gain per meal in environments where food is scarce.

Animals↗
PubMed1984

Electrical activity of the reticular formation during aversive and appetitive conditioning in rats.

Evoked potentials (EP) to a conditioned stimulus (CS) were recorded from several parts of the reticular formation (RF), the midbrain central gray (CG), the occipital cortex (OC), the basolateral amygdala and the ventrobasal thalamus during appetitive and aversive classical conditionings in rats. In addition, single unit activity to rewarding CS (+) and punishing CS (-) in a single discriminative classical conditioning was recorded from RF, OC, CG and the tectum. In the EP study, peak-to-peak (p-p) amplitudes, especially of the pontine RF, increased in the initial phase of pre-conditioning, in aversive conditioning and in appetitive conditioning but not in aversive pseudo-conditioning. The p-p amplitude in the pontine RF might reflect an amount of stimulus value the animal received. Slow negative potentials after CS presentation in RF was a reflection of body movements, indicating heavy involvement of RF in motor functions. In the single unit studies, cells which selectively responded to the CS (-) were more frequently found in the medial tegmental area close to the median raphe nucleus as compared to other areas. These results were considered to indicate high sensitivity of RF to the significance of the stimulus, and also the involvement of the medial tegmental area close to the median raphe nucleus in aversive emotional processes. Although many studies employing stimulation or lesion techniques have reported the steady relation between aversive emotional responses and CG, no supporting result was obtained in the present experiments.

Affect↗
PubMed1985

Diuresis and reduction of salt appetite by lateral ventricular infusions of atriopeptin II.

Infusions of 60 pmol/h atriopeptin II into the lateral ventricles stimulated urine flow in both normally hydrated and sodium depleted conscious rats without any increase in the excretion of sodium, potassium or total solutes. The urinary sodium concentration and osmolality both declined significantly. In addition to the renal effects, cerebroventricular infusions of 60 pmol/h atropeptin II reduced salt appetite in rats following depletion of sodium by combined treatment with furosemide diuresis and low sodium diet. Neither 60 nor 600 pmol/h doses had any effect on urine volume or concentration during intravenous infusions, so the effects appear to be mediated by the central nervous system (CNS). Atriopeptins may act through the CNS to facilitate reduction of extracellular volume in synergy with peripheral natriuresis: by increasing urine flow independently from natriuresis; and by restricting further expansion of extracellular volume by reducing salt appetite.

Animals↗
PubMed1989

The effects of sodium appetite on the responses of cells in the zona incerta to the sight or ingestion of food, salt and water in sheep.

Single-unit recordings were made from neurones in the zona incerta (ZI) of conscious sheep in response to the sight/visual approach or ingestion of various foods, salts and water. Animals were given parotid fistulae so that effects of sodium appetite, induced by not replacing the sodium lost in the saliva, could be assessed. When sodium depletion was prevented by giving the animals 1% sodium bicarbonate in their drinking water, the majority of cells (45 out of 49) responded most strongly to the sight or visual approach of food compared to water or salt. Four cells responded best to the sight of water, but none to the sight of salt and salt solutions. When a sodium appetite was stimulated, by removing the 1% sodium bicarbonate replacement for 4-6 days, there was a significant change in response profiles of ZI cells. The majority of cells responded most strongly to the sight of salts or salt solutions (35 out of 49) and significantly fewer cells responded most strongly to food (8 out of 49). The number of cells responding primarily to water was not affected (6 out of 49). For 3 cells responding to salts it was shown that, after repeated ingestion of salt over several hours, food became a more potent stimulus. A similar decreased response to foods during sodium depletion, and an increased one to salts, was seen in ZI cells which responded to the ingestion of both solids and liquids. These results show that changing an animal's motivational state produces significant changes in the responses of cells in the ZI responding to the sight or visual approach of substances.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1990

Subfornical organ lesion decreases sodium appetite in the sodium-depleted rat.

The effect of subfornical organ (SFO) lesion on various models of ingestive behaviour was investigated in rats. Intake of water after 24 h water deprivation or systemic administration of hypertonic NaCl were not altered by SFO lesions. Intake of food or water after 24 h of food deprivation were not altered by SFO lesions. Intake of NaCl after furosemide-induced Na depletion was decreased by ablation of the SFO. This decrease in Na intake was ameliorated by pretreatment with a low dose of captopril. These results suggest that the SFO is involved in Na intake after Na depletion, but not in water or food intake following periods of water or food deprivation, respectively. The observation that a low dose of captopril can eliminate the decrease in Na appetite which occurred subsequent to SFO lesion suggests that other brain areas may also participate in Na-depletion-induced Na appetite.

Animals↗
PubMed1985

Dehydration-induced sodium appetite in rats.

The effect of 24 hr water deprivation on Na balance was studied in rats. Under baseline conditions, the animals had free access to food and water. During water deprivation, Na excretion was increased, Na intake (i.e., food intake) was decreased and Na deficits of 0.8-1.0 mmol were incurred. During the 24 hr period immediately following the deprivation period when water was returned, Na excretion was decreased and Na balance was restored to baseline or pre-deprivation level. In a second series of experiments, under baseline conditions, the animals had free access to food, water and 0.5 M NaCl. During water deprivation with NaCl solution withheld, Na excretion was not changed relative to baseline but Na deficits of 0.8-1.0 mmol were incurred due to decreased Na intake. During the 24 hr period immediately following deprivation when both water and NaCl solution were returned, intake of the hypertonic NaCl solution was increased and Na balance was restored. In a third series of experiments, under baseline conditions, the animals had free access to food, water, 0.5 M NaCl, 0.5 M KCl, 0.25 M of MgCl2 and 0.25 M CaCl2. During the 24 hr period following water deprivation and also the withholding of the electrolyte solutions, the appetite induced was predominantly for NaCl. The results suggest that the Na appetite observed subsequent to a period of water deprivation may be due to Na deficiency.

Animals↗
PubMed1988

Salt appetite during pregnancy in sheep.

Sodium preference was examined in three groups of sheep which had all sustained two consecutive pregnancies and lactations on either adequate sodium intakes (group C) or low sodium diets (B and C). Group B received a potassium supplement as well as a low sodium diet during the present experiment. No convincing or sustained increase in sodium preference resulted from the reduction in body sodium caused by pregnancy and lactation in group B or C, whether the sodium solutions offered were 40 or 300 mmol/l. In a second experiment, sodium preference (sodium bicarbonate, 40 mmol/l) was studied throughout pregnancy in sheep on low or adequate sodium diets, also non-pregnant controls on low sodium diets. Again, pregnancy on a low sodium intake failed to intensify salt appetite except for a transient (but significant) peak around d90, close to the peak of aldosterone secretion; a similar increase in preference occurred on the adequate sodium diet. However, salt appetite failed to intensify during the period of peak sodium demand (the last third of pregnancy) whereas renal and faecal sodium conservation are appropriately increased.

Animals↗
PubMed1993

Adrenalectomy enhances the anorectic effect of dexfenfluramine: relation to mineralocorticoids and salt appetite.

A previous observation that adrenalectomized (ADX) rats were more anorectic and lost more weight than intact controls when treated with the serotonergic agent, d,l-fenfluramine, was confirmed using a high dose of the more selective d-enantiomer, dexfenfluramine (DFEN). However, ADX rats were not more anorectic than intact controls to a lower dose of DFEN. The extreme weight loss at high doses was accompanied by a loss of appetite for NaCl solution. The rapid deterioration of these animals may have been due to excessive loss of sodium ions and extracellular fluid volume, although this was not assessed directly. This interpretation was supported in a second study in which treatment of ADX rats with a selective mineralocorticoid, which eliminates both the need and appetite for NaCl, normalized weight loss during DFEN treatment. These data do not support the idea of an interactive role of glucocorticoids and brain serotonin in anorexia. The density of serotonin uptake sites in frontal cortex was reduced by DFEN in a dose-dependent manner, but did not differ between ADX and intact control groups.

Adrenal Glands↗
PubMed1993

Hepatic vagotomy does not disrupt the normal satiation of NaCl appetite.

The necessity of the hepatic branch of the vagus nerve for the normal satiation of NaCl intake under the condition of sodium depletion was tested. Sham- or hepatic-vagotomized male, Long-Evans rats were sodium depleted by injection with Lasix (furosemide, 10 mg) and were maintained overnight on sodium-deficient diet and water. The intake of 0.3 M NaCl during a 2-h salt appetite test was not significantly different between the sham- and hepatic-vagotomized groups. In a second group of sham- or hepatic-vagotomized rats, a load of 7.5 ml of 0.5 M NaCl was given by gavage at 15 or 90 min prior to a 1-h NaCl appetite test. The preload decreased NaCl intake equivalently in both groups. Gastric emptying of a preload of NaCl at 15 and 90 min was also the same for sham- and hepatic-vagotomized rats. Thus, the hepatic branch of the vagus nerve is not necessary for the normal short-term satiation of NaCl intake under the condition of acute sodium depletion produced by furosemide.

Animals↗
PubMed1995

An angiotensin-independent, hypotension-induced, sodium appetite in the rat.

We have investigated the role of peripheral angiotensin II in the generation of hypotension (without hypovolaemia)-induced salt intake in rats treated with an IV infusion of the quaternary ammonium peripheral ganglion blocker Penthonium. At a dose of 15.4 mg/ml this compound induces a significant decrease in blood pressure from the beginning of the infusion. Intake of 3% NaCl was significantly increased only on the first day (1.7 +/- 0.3 ml, n = 7, p < 0.01 vs. the day before) and this induced salt appetite was not altered (2.3 +/- 0.9 ml, n = 7, p < 0.05 vs. the day before) by intracerebroventricular administration of a nonpeptide AII-type 1 receptor specific antagonist, Losartan, at a dose known to block AII-induced drinking (250 ng). We conclude from these results that AII liberated in response to the hypovolaemia is probably not responsible for the subsequent induced intake of NaCl which may be the result of a direct barosensitive input to the salt appetite centers of the brain.

Angiotensin II↗
PubMed1994

Neural coding of aversive and appetitive gustatory stimuli: interactions in the hamster brain stem.

There is increasing evidence, both electrophysiological and behavioral, that bitter and sweet stimuli drive parallel pathways in the gustatory brainstem. Here we report two lines of investigation that suggest significant interactions among these parallel systems. First, responses recorded from single cells in the hamster's parabrachial nuclei (PbN) show that quinine hydrochloride (QHCl) produces a substantial suppression (> 40%) of the responses of PbN cells to sucrose. Sucrose stimulation has a reciprocal suppressive effect on the response to QHCl. These results imply that aversive and appetitive stimuli produce mutual inhibition in the gustatory system; studies of the chorda tympani nerve response suggest that this inhibition likely arises within the brainstem. A second line of investigation, using both an in vitro brainstem slice preparation and in vivo pharmacological manipulations of cells in the hamster NST, has demonstrated an inhibitory network within the rostral NST that plays a role in the modulation of taste activity. Patch-clamp and extracellular recording studies in vitro show that cells within the rostral central subdivision of the NST are inhibited by gamma-aminobutyric acid (GABA); this mediation is largely through the GABAA receptor subtype. Here we show that responses to taste stimulation recorded extracellularly from NST cells in vivo can be inhibited by local microinjections of GABA; this inhibition is blocked by the GABAA receptor antagonist bicuculline methiodide. Responses to sucrose are significantly more inhibited than those to NaCl or KCl. These combined lines of evidence show that appetitive and aversive stimuli activate mutually inhibitory systems within the brainstem and suggest that the basis for this interaction is a GABAergic inhibitory network within the NST.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Methotrexate does not interfere with an appetitive Pavlovian conditioning task in Sprague-Dawley rats.

There has been considerable interest in developing an animal model of the neuropsychological toxicity of chemotherapeutic agents used in the treatment of patients with cancer, especially children, since these agents often cause significant, long-term neuropsychological deficits. Yanovski, Packer, Levine, Davidson, Micalizzi, D'Angio (13) recently proposed such a model based on their finding that methotrexate retarded the formation of aversive Pavlovian excitatory associations. The present experiment examined the generality of methotrexate induced cognitive impairments by testing rats in Appetitive Pavlovian Conditioning tasks and a Conditioned Taste Aversion paradigm. The results of our study revealed no impairment following methotrexate exposure on the Appetitive Pavlovian tasks or on the Taste Aversion task, relative to two control conditions. While there were a number of methodological differences between the present experiment and those conducted by Yanovski et al. (13), the present results question the robustness and generality of Yanovski's et al. (13) animal model.

Animals↗