Microstructural Analysis Of Licking Behavior Research Articles

Characterizing Hedonic Responses to Flavors Paired with Internal Pain and Nausea through the Taste Reactivity Test in Rats.

Feeding behavior is a complex experience that involves not only sensory (i.e., visual, odor, taste, or texture) but also affective or emotional aspects (i.e., pleasure, palatability, or hedonic value) of foods. As such, behavioral tests that assess the hedonic impact of foods are necessary to fully understand the factors involved in ingestive behavior. In this protocol, we use the taste reactivity (TR) test to characterize the hedonic responses of rats to flavors paired with either lithium chloride-induced nausea or internal pain produced by hypertonic NaCl, two treatments that reduce voluntary consumption. This application of the TR test demonstrates how emetic and non-emetic (somatic pain in particular) treatments produce dissociable patterns of hedonic reactions to fluids: only emetic treatments result in the production of aversive orofacial responses, reflecting conditioned nausea, whereas somatic pain produces immobility, reflecting conditioned fear. Other methods, such as the microstructural analysis of licking behavior, do not reliably distinguish conditioned nausea and fear, a key advantage of the more selective TR procedure. This protocol also contains guidance for adaptation to other species and designs.

Wistar Kyoto Rats Display Anhedonia In Consumption but Retain Some Sensitivity to the Anticipation of Palatable Solutions.

The Wistar Kyoto (WKY) rat has been proposed as a model of depression-like symptoms. However, anhedonia—a reduction in the response to normatively rewarding events—as a central depression symptom has yet to be fully assessed in this model. We compared WKY rats and Wistar controls, with stress-susceptibility examined by applying mild unpredictable stress to a subset of each group. Anhedonia-like behavior was assessed using microstructural analysis of licking behavior, where mean lick cluster size reflects hedonic responses. This was combined with tests of anticipatory contrast, where the consumption of a moderately palatable solution (4% sucrose) is suppressed in anticipation of a more palatable solution (32% sucrose). WKY rats displayed greatly attenuated hedonic reactions to sucrose overall, although their reactions retained some sensitivity to differences in sucrose concentration. They displayed normal reductions in consumption in anticipatory contrast, although the effect of contrast on hedonic reactions was greatly blunted. Mild stress produced overall reductions in sucrose consumption, but this was not exacerbated in WKY rats. Moreover, mild stress did not affect hedonic reactions or the effects of contrast. These results confirm that the WKY substrain expresses a direct behavioral analog of anhedonia, which may have utility for increasing mechanistic understanding of depression symptoms.

Moxonidine into the lateral parabrachial nucleus modifies postingestive signals involved in sodium intake control

The activation of α2-adrenoceptors with bilateral injections of moxonidine (α2-adrenoceptor and imidazoline receptor agonist) into the lateral parabrachial nucleus (LPBN) increases 1.8% NaCl intake induced by treatment with furosemide (FURO)+captopril (CAP) subcutaneously. In the present study, we analyzed licking microstructure during water and 1.8% NaCl intake to investigate the changes in orosensory and postingestive signals produced by moxonidine injected into the LPBN. Male Sprague–Dawley rats were treated with FURO+CAP combined with bilateral injections of vehicle or moxonidine (0.5nmol/0.2μl) into the LPBN. Bilateral injections of moxonidine into the LPBN increased FURO+CAP-induced 1.8% NaCl intake, without changing water intake. Microstructural analysis of licking behavior found that this increase in NaCl intake was a function of increased number of licking bursts from 15 to 75min of the test (maximum of 49±9bursts/bin, vs. vehicle: 2±2bursts/bin). Analysis of the first 15min of the test, when most of the licking behavior occurred, found no effect of moxonidine on the number of licks/burst for sodium intake (24±5licks/burst, vs. vehicle: 27±8licks/burst). This finding suggests that activation of α2-adrenoceptors in the LPBN affects postingestive signals that are important to inhibit and limit sodium intake by FURO+CAP-treated rats.

Decreased consumption of sweet fluids in mu opioid receptor knockout mice: a microstructural analysis of licking behavior

Evidence suggests that the palatability of food (i.e., the hedonic impact produced by its sensory features) can promote feeding and may underlie compulsive eating, leading to obesity. Pharmacological studies implicate opioid transmission in the hedonic control of feeding, though these studies often rely on agents lacking specificity for particular opioid receptors. Here, we investigated the role of mu opioid receptors (MORs) specifically in determining hedonic responses to palatable sweet stimuli. In Experiment 1, licking microstructure when consuming sucrose solution (2 to 20%) was compared in MOR knockout and wildtype mice as a function of sucrose concentration and level of food deprivation. In Experiment 2, a similar examination was conducted using the palatable but calorie-free stimulus sucralose (0.001 to 1%), allowing study of licking behavior independent of homeostatic variables. In Experiment 1, MOR knockout mice exhibited several alterations in sucrose licking. Although wildtype mice exhibited a twofold increase in the burst length when food deprived, relative to the nondeprived test, this aspect of sucrose licking was generally insensitive to manipulations of food deprivation for MOR knockout mice. Furthermore, during concentration testing, their rate of sucrose licking was less than half that of wildtype mice. During sucralose testing (Experiment 2), MOR knockout mice licked at approximately half the wildtype rate, providing more direct evidence that MOR knockout mice were impaired in processing stimulus palatability. These results suggest that transmission through MORs mediates hedonic responses to palatable stimuli, and therefore likely contributes to normal and pathological eating.

Effects of benzodiazepine receptor ligands on the ingestion of sucrose, intralipid, and maltodextrin: an investigation using a microstructural analysis of licking behavior in a brief contact test.

Microstructural analysis of licking behavior in the rat was conducted (a) to describe in detail the characteristics of benzodiazepine-induced changes in ingestion and (b) to determine if the changes are consistent with an alteration in palatability. The effects of the benzodiazepine receptor (BZR) agonist midazolam (0.3-3 mg/kg), and the partial inverse agonist Ro 15-4513 (0.3-3 mg/kg), on licking for several concentrations of sucrose, Intralipid, and maltodextrin in a brief contact test were investigated. Midazolam increased the total number of licks for all 3 fluids; conversely, Ro 15-4513 decreased the total number of licks. Midazolam increased mean bout duration for sucrose and maltodextrin drinking and there was a trend toward a similar effect with Intralipid drinking. Ro 15-4513 reduced mean bout duration for all 3 test fluids. These data are discussed in terms of bidirectional changes in fluid palatability by drug actions at BZRs.

Effects of benzodiazepine receptor ligands on the ingestion of sucrose, intralipid, and maltodextrin: An investigation using a microstructural analysis of licking behavior in a brief contact test.

Effects of benzodiazepine receptor ligands on the ingestion of sucrose, intralipid, and maltodextrin: An investigation using a microstructural analysis of licking behavior in a brief contact test.

Analytical issues in the evaluation of food deprivation and sucrose concentration effects on the microstructure of licking behavior in the rat.

A microstructural analysis of licking behavior in nondeprived and 23-hr food-deprived rats (n = 15) presented with various sucrose solutions (0.03-1.0 M) in daily single-bottle, 1-hr sessions was conducted. Food deprivation and concentration interacted to increase total licks. The effects of food deprivation and concentration on burst size (BS), burst number (BN), and other parameters varied as a function of the pause criterion (PC; 0.3-100 s) used to define licking bursts. A rationale for selecting a 1-s PC for further analysis is presented. Despite the lack of correlations between temporally contiguous burst and pause combinations, mean BS decreased and pause duration increased as meals progressed. At the 1-s PC, BS increased linearly with concentration, implying that this microstructural parameter is influenced in part by taste. Food deprivation did not affect BS but rather increased BN and proportionally extended the meal duration.

Effects of the benzodiazepine receptor inverse agonist Ro 15-4513 on the ingestion of sucrose and sodium saccharin solutions: A microstructural analysis of licking behavior.

Effects of the benzodiazepine receptor inverse agonist Ro 15-4513 on the ingestion of sucrose and sodium saccharin solutions: A microstructural analysis of licking behavior.

Effects of the benzodiazepine receptor inverse agonist Ro 15-4513 on the ingestion of sucrose and sodium saccharin solutions: a microstructural analysis of licking behavior.

The effects of the benzodiazepine receptor partial inverse agonist Ro 15-4513 on consumption of either a 1% sucrose solution or a 0.1% sodium saccharin solution in nondeprived male rats was examined. A video-recording approach was adopted in which licks were counted in a frame-by-frame analysis. Ro 15-4513 (1-10 mg/kg) caused a significant decrease in the intake of both sucrose and saccharin solutions that was associated with a reduction in the initial rate of licking. There was a decrease in the total duration of drinking, total licks, and number of bouts for both sucrose and saccharin. For sucrose, mean bout duration was significantly reduced, although this was not so for saccharin. Intrabout lick rate, the latency to engage in drinking, and the postdrinking time were not affected for either sucrose or saccharin. These data are consistent with previous evidence that strongly suggests that benzodiazepines influence palatability.