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A C Spector

Publications and source records attributed to A C Spector.

52 records · Page 3Linked to original sources
PubMed1992

Parabrachial gustatory lesions impair taste aversion learning in rats.

Lesions in the gustatory zone of the parabrachial nuclei (PBN) severely impair acquisition of a conditioned taste aversion (CTA) in rats. To test whether this deficit has a memorial basis, intact rats (n = 15) and rats with PBN lesions (PBNX; n = 10) received seven intraoral taste stimulus infusions (30 s, 0.5 ml) distributed over a 30.5-min period after either LiCl or NaCl injection. This task measures the rapid formation of a CTA and has minimum demands on memory. LiCl-injected intact rats progressively changed their oromotor response profile from one of ingestion to one of aversion. NaCl-injected intact rats did not change their ingestive pattern of responding. In contrast, there was no difference between LiCl- and NaCl-injected PBNX rats. These same PBNX rats failed to avoid licking the taste stimulus when tested in a different paradigm. A simple impairment in a memorial process is not likely the basis for the CTA deficit.

Afferent Pathways↗
PubMed1992

A quantitative comparison of taste reactivity behaviors to sucrose before and after lithium chloride pairings: a unidimensional account of palatability.

Alterations in the motivation to ingest sucrose can be quantified by measuring the number and type of oral motor and somatic responses (i.e., taste reactivity [TR]) that are elicited by sucrose. In 2 experiments, rats had intraorally infused sucrose paired with LiCl injections for several trials, or they were injected with LiCl and had sucrose infused every 5 min during the 30-min postinjection period (data from Spector, Breslin, & Grill, 1988). In both experiments, ingestive TR responses decreased, whereas aversive TR responses increased over trials. Individual response components that comprise the ingestive and aversive categories followed the same trends of increase or decrease but changed at different rates as a function of number of trials or exposures. Overall, the array of response components could be projected onto a single unidimensional scale of palatability to capture the motivational states that ranged from acceptance to rejection.

Animals↗
PubMed1992

Salt taste discrimination after bilateral section of the chorda tympani or glossopharyngeal nerves.

Gustatory deafferentation of the anterior tongue by bilateral section of the chorda tympani nerve, which removes only 15% of the total taste buds in the rat, severely impaired the rat's ability to discriminate NaCl from KCl. The discrimination deficit was selective. Denervated rats were able to discriminate sucrose from quinine. Despite eliminating four times as many taste buds by bilateral section of the glossopharyngeal nerve, posterior lingual deafferentation had no effect on NaCl vs. KCl discrimination performance. Collectively, these data suggest that afferents in the chorda tympani nerve provide the highest degree of disparity between the peripheral signals representing NaCl and KCl. Electrophysiological findings of others implicate the sodium-specific afferents that appear to exclusively exist in the chorda tympani nerve as the critical elements subserving the NaCl vs. KCl discrimination.

Animals↗
PubMed1992

Dynamics of gastric emptying during and after stomach fill.

Gastric contents were sampled at various points during and after intragastric infusions of glucose solution (6.25, 12.5, 25%) delivered at rates typical of normal ingestion in the rat. The postinfusion results were consistent with those reported in the literature in that glucose solute emptied at a relatively stable rate over time and across stimulus concentrations. During fill (1.0 ml/min; experiment 1), by contrast, solute (caloric) emptying rate increased about threefold as stimulus concentration was raised. For each concentration, emptying rate was uniformly higher during than after fill (approximately 4 times higher at the lowest concentration). In experiment 2, gastric emptying rate during 12-min intragastric infusions of 12.5% glucose varied directly with the volumetric rate (0.5, 1.0, 2.0 ml/min) at which they were delivered. These results show that different rules govern gastric emptying during and after stomach fill. The results also suggest that a large proportion of a liquid meal may empty before feeding is terminated and that variations in the rate of ingestion could affect the gastric/postgastric distribution of ingesta and, in turn, the satiation process.

Analysis of Variance↗
PubMed1990

A new gustometer for psychophysical taste testing in the rat.

This paper provides a detailed description of a gustometer designed and constructed in our laboratory for psychophysical taste testing in rats. The gustometer features: a) 12 stimulus channels, b) the ability to deliver a specified volume of a taste stimulus per lick (e.g., 5 microliters), c) the accurate measurement of immediate licking responses, d) an automatic drinking spout cleaning mechanism for use between taste trials, and e) complete computer control and analysis. Complete plans and electronic schematics are included. In addition, results from contamination tests are presented verifying the reliability of the stimulus delivery system. The usefulness and versatility of this apparatus in a variety of behavioral tasks is discussed.

Animals↗
PubMed1990

Ingestion rate as an independent variable in the behavioral analysis of satiation.

A novel intake testing paradigm, allowing explicit adjustment of the rate of sucrose ingestion via intraoral delivery, was used to investigate the effects of ingestion rate on ingestion duration and amount consumed. In experiment I, 12 rats were tested under each of three sucrose concentrations (0.1, 0.3, and 1.0 M) delivered at each of four rates (0.5, 1.0, 1.5, and 2.0 ml/min). For each stimulus concentration, intraoral intake varied as a decreasing linear function of ingestion rate (infusion rate). In experiment II, a second (part B) infusion (0.5, 1.0, or 1.5 ml/min) was initiated 30 s after an initial (part A) infusion (0.5, 1.0, or 1.5 ml/min) of the same stimulus was rejected. Amount consumed during the part B infusion was substantial only when the part B infusion rate was lower than that of part A. Quantitative analysis of experiment II indicated that across sessions with common part B infusion rates, total session intake remained stable regardless of 1) whether the part A ingestion rate was greater than or equal to that of part B, 2) systematic differences in part A intake and duration, 3) differences in total session duration, and 4) differences in average ingestion rate for the session (total session intake/total session duration). The behavioral results are discussed in relation to the analysis of satiety under traditional intake testing paradigms and to gastric and postgastric theories of satiety.

Analysis of Variance↗
PubMed1990

Chemospecific deficits in taste detection after selective gustatory deafferentation in rats.

Electrophysiological data support the existence of sodium-specific taste receptors that appear to be limited to the anterior tongue. However, previous behavioral findings suggest that bilateral transection of the chorda tympani nerve (CTn) has minimal consequences on NaCl intake and preference. This study employed a conditioned avoidance procedure to measure detection thresholds to NaCl and sucrose both before and after bilateral transection of the CTn. Rats were trained to maintain spout contact in response to water presentations (70 microliters) and to avoid spout contact when a taste solution (70 microliters) was presented. In experiment 1, all rats (n = 3) showed statistically significant impairments in the detectability of NaCl after bilateral section of the CTn. The mean increase in the NaCl detection threshold was 1.41 log units. In contrast, sucrose threshold in these same rats was marginally affected by CTn section (mean increase = 0.22 log units). Experiment 2 (n = 4) replicated the findings of the first experiment. The mean increase in the NaCl detection threshold was 2.23 log units. Sucrose threshold in these rats was, again, only marginally affected by CTn section (mean increase = 0.83 log units). Histological examination of the anterior tongue from the rats in experiment 2 indicated that the CTn transections were complete. These findings reveal that the anterior oral receptive field (innervated by the CTn) containing only 15% of the total taste bud population is critical for the normal detection of NaCl.

Afferent Pathways↗
PubMed1988

Taste reactivity as a dependent measure of the rapid formation of conditioned taste aversion: a tool for the neural analysis of taste-visceral associations.

Several explanations may account for deficits in the ability of animals to form taste aversions following neural manipulations. These encompass impairments in conditioned stimulus (CS) and unconditioned stimulus (US) processing, conditioned response (CR) measurement, and expression, memory, and taste-visceral integration. A behavioral procedure that aids in the distinction between some of these possibilities is presented. In Experiment 1, 10 rats received seven intraoral (IO) infusions of sucrose (30 s, 0.55 ml) spaced every 5 min starting immediately after the injection of 3.0 mEq/kg of lithium chloride (LiCl). Control rats (n = 12) were treated identically except that they were injected with sodium chloride (NaCl). Oromotor and somatic taste reactivity behaviors were videotaped and analyzed. Lithium-injected rats systematically decreased their ingestive taste reactivity behavior over time, whereas aversive behavior increased. Control rats maintained high and stable levels of ingestive responding and demonstrated virtually no aversive behavior over the 30-min period following sodium injection. Rats were tested several days later for the presence of a conditioned taste aversion (CTA). Rats previously injected with lithium during sucrose infusions demonstrated significantly more aversive behavior than the control group, which demonstrated none. There were no differences in the level of ingestive behavior displayed by the two groups on the CTA test. Experiment 3 revealed that when similarly treated rats were tested for a CTA while in a lithium-induced state, a difference in the ingestive behavior between the two groups was observed. In Experiment 2, naive rats were injected with either NaCl or LiCl but did not receive their first sucrose infusion until 20 min later. These rats also received sucrose infusions at 25 and 30 min postinjection. There were no differences in the taste reactivity behavior displayed by lithium- or sodium-injected rats during any of the sucrose infusions. Collectively, these findings indicate that rats dramatically change their oromotor responses to sucrose during the period following LiCl administration, provided that the infusions start immediately after injection. Furthermore, this time-related behavioral change is predominantly attributable to associative processes. This paradigm can be useful in distinguishing between neural manipulations that affect the establishment of taste-visceral associations from others that affect the animal's ability to retain such associations over the commonly employed 24-hr conditioning-test interval.

Afferent Pathways↗
PubMed1986

Radiation-induced taste aversion: effects of radiation exposure level and the exposure-taste interval.

Radiation-induced taste aversion has been suggested to possibly play a role in the dietary difficulties observed in some radiotherapy patients. In rats, these aversions can still be formed even when the radiation exposure precedes the taste experience by several hours. This study was conducted to examine whether increasing the radiation exposure level could extend the range of the exposure-taste interval that would still support the formation of a taste aversion. Separate groups of rats received either a 100 or 300 R gamma-ray exposure followed 1, 3, 6, or 24 h later by a 10-min saccharin (0.1% w/v) presentation. A control group received a sham exposure followed 1 h later by a 10-min saccharin presentation. Twenty-four hours following the saccharin presentation all rats received a series of twelve 23-h two-bottle preference tests between saccharin and water. The results indicated that the duration of the exposure-taste interval plays an increasingly more important role in determining the initial extent of the aversion as the dose decreases. The course of recovery from taste aversion seems more affected by dose than by the temporal parameters of the conditioning trial.

Animals↗
PubMed1984

A detailed analysis of sucrose drinking in the rat.

The present report represents an initial attempt to examine and quantify the eating and drinking patterns of rats presented with water, laboratory chow, and sucrose solution for 23 hours. The concentration of the sucrose solution was systematically increased (0.10 M, 0.25 M, 0.5 M, 1.0 M) with a single concentration being presented to rats in four-day blocks. As has been previously shown, total intake (ml) of sucrose solution increased with concentration to a peak at 0.25 M and then decreased with further rises in concentration. Calories consumed from sucrose monotonically increased with concentration, reaching a maximum at 0.50 M. As calories consumed from sucrose increased with rising concentration, chow intake monotonically decreased. This compensatory decrease in chow intake was primarily attributable to decreases in nighttime chow consumption when the concentration of sucrose available was less than or equal to 0.25 M; when the concentration was greater than 0.25 M, further reductions in chow intake occurred during the day. Moreover, the decrease in chow intake was due solely to a reduction in the number of chow bouts. As the concentration of sucrose increased, the day-to-night ratio of sucrose intake approached unity. Bout volume increased with concentration to a broad peak spanning 0.25-0.5 M, and then decreased with 1.0 M. Bout duration changed with sucrose concentration such that the bout drinking rate (ml/min) was seen to monotonically increase, reaching a stable maximum at 0.5 M. Since the caloric intake per sucrose bout progressively increased with each rise in concentration, the asymptotic portion of the curve describing calories consumed from sucrose was attributable to alterations in sucrose bout number and not sucrose bout size.

Animals↗
PubMed1983

The effect of postconditioning CS experience on recovery from radiation-induced taste aversion.

Seventy-two hours after saccharin (CS) was paired with either a 100R or sham radiation exposure, rats received a 0-, 3-, 6-, 12-, 24-, or 46-hour saccharin-alone presentation followed by a 23-hour two-bottle preference test. Generally, faster recovery from the aversion was observed in animals receiving longer CS-alone presentations. The present procedure differs from previous work done with other toxins in that animals were not fluid-deprived during the postconditioning period. This enabled animals to constantly control the volume, duration, and inter-bout interval of the saccharin drinking episodes independent of any experimentally imposed drinking schedule. In addition, the two-bottle test provided a sensitive measure of the status of the saccharin aversion following the saccharin-alone presentation.

Animals↗
PubMedDate not supplied

Glossopharyngeal nerve transection reduces quinine avoidance in rats not given presurgical stimulus exposure.

Behavioral studies on the effects of bilateral glossopharyngeal nerve (GL) transection on quinine responsiveness have yielded mixed results. These differences may be explained by the presence or absence of presurgical exposure with the tastant. In the present experiment we measured unconditioned licking to quinine in rats that had no exposure to quinine before surgery. Rats were water deprived and trained to lick water during 10 s trials in an automated gustometer. Next, they were divided into groups that received either GL transection or sham surgery (CON). Following recovery, the water-deprived rats were presented with seven concentrations of quinine hydrochloride (0.003-3 mM) and distilled water. The number of licks to each tastant was averaged over three days of testing. Rats with GL transection licked significantly more to the higher concentrations of quinine relative to CON rats, resulting in a 0.44 log10 unit shift in the quinine concentration-response curve. These results when considered with prior work suggest that experience before nerve transection may have a small protective effect on taste-guided behavioral responsiveness to quinine in rats.

Animals↗
PubMedDate not supplied

Gustatory function in the parabrachial nuclei: implications from lesion studies in rats.

In rodents, third order gustatory neurons reside in the parabrachial nuclei of the dorsal pons. Lesions in this area of the brain have a variety of consequences on taste-related behaviors. Some behaviors are severely impaired, such as the expression of either conditioned taste aversion or depletion-induced sodium appetite. Other taste-based behaviors are less affected or not influenced at all. Although the lesion-behavior approach possesses serious methodological limitations, the constellation of findings from studies employing this experimental strategy in the PBN has promising implications. Foremost among these is the suggestion that the neural circuitry subserving performance in some of these taste-guided behavioral paradigms is dissociable. This paper critically reviews this body of behavioral research and discusses the conceptual ramifications of the results.

Animals↗