Christopher L. Cunningham

Effects of concentration of ethanol injected intraperitoneally on taste aversion, body temperature, and activity.

Levels of ethanol-induced conditioned taste aversion and hypothermia were found to be directly related to the concentration of fixed amounts of ethanol injected i.p. in a range of doses (1.0–1.8 g/kg) and concentrations (8–32% v/v) commonly used in behavioral studies. No effect of ethanol concentration on locomotor activity was obtained. The results of blood-ethanol determinations indicate that a given dose of ethanol is absorbed more rapidly, and thus reaches greater peak levels, when injected in a higher concentration. Thus ethanol dosage might be better manipulated by varying the volume of a single concentration rather than by altering concentration. In this way, dose-response data will not be obscured by concentration-induced differences in absorption.

Flavor and location aversions produced by ethanol.

To test the possibility that ethanol might “simultaneously” be rewarding and punishing, male albino rats received five conditioning trials wherein access to saccharin was followed by injection of ethanol (1.5 g/kg) and placement in a distinctive compartment for 30 min. On alternate days, they were exposed to a second compartment without injection. Control rats received a similar treatment except that access to saccharin never preceded ethanol injection. Aversions were established to both flavor and location, and flavor did not interfere with conditioning of location aversion. Thus, ethanol appeared to have a uniformly negative effect.

Spatial aversion conditioning with ethanol

To determine whether dose level affected ethanols ability to establish a preference or aversion for an associated spatial location, two groups of male albino rats each received five pairings of an IP injection of ethanol (1 or 2 g/kg) with exposure to a distinctive compartment for 15 min. On alternate days, each rat was exposed to a different compartment after a saline injection. A choice test indicated that aversions were established at both dose levels, and thus failed to confirm a previous report of conditioned location preference at the lower dose level.

Alcohol as a cue for extinction: State dependency produced by conditioned inhibition.

A conditioned-emotional-response (CER) paradigm was used in two experiments to evaluate the effects of alcohol on extinction. In both experiments, rats received tone-shock pairings without alcohol and then received extinction trials either with or without alcohol (injections of saline, .75 or 1.5 g/kg ethanol). The high dose of alcohol suppressed baseline barpressing for food reward, but there was only weak evidence (Experiment 2) that it enhanced responding during the tone early in extinction. In both experiments, extinction of CER under the high alcohol dose was found to be state dependent, that is, post-extinction tests after saline injection showed a reinstatement of suppression to the tone. Experiment 2 indicated that this effect could be attributed to alcohol’s becoming a conditioned inhibitory stimulus as a result of its association with extinction. This supports the general suggestion that situational stimuli normally become inhibitory during the course of simple extinction and may have implications for the role that state-dependent learning plays in drug dependence.

Excitatory and inhibitory consequences of explicitly unpaired and truly random conditioning procedures on heart rate in rats

A comparison was made of heart-rate (HR) responses of restrained rats to CSs that were part of an explicitly unpaired or a truly random control procedure. Subsequent to these procedures, an assessment was made of the relative capacities of these CSs to affect an established HR CR in a combined-cue paradigm and to impede the development of a HR CR in a reversal-conditioning situation. The principal findings were (1) that the explicitly unpaired and truly random CSs generated HR responses of opposite direction, i.e., HR acceleration vs. HR deceleration, respectively, and (2) that conditioning of a decelerative HR CR to the CS that had earlier been employed in the explicitly unpaired procedure was retarded compared to what was obtained to the truly random CS. The two CSs did not have reliably different effects in the combined-cue test. It was suggested that the truly random CS may have produced both associative and nonassociative influences on HR. It was hypothesized further than the explicitly unpaired CS may have acquired the capacity to function as a conditioned inhibiting stimulus.

A digital system for recording startle, responses in small animals

An easily constructed, isometric startle-recording system is described. The animal enclosure is attached to a plywood board-which, in ten, is mounted in a “springboard” arrangement. Movement is detected by a phonocartridge mounted beneath the chamber, and a digital record of this movement is obtained through the use of a voltage-to-frequency converter. A brief experiment in which the system was used to assess the rat’s reaction to electric footshock is also presented.

Alcohol interacts with flavor during extinction of conditioned taste aversion

Intraperitoneal injections of ethanol (1.2 g/kg) given 30 min before taste-aversion extinction trials retarded extinction of aversion to a quinine-hydrochloride solution, did not affect extinction of aversions to sucrose or hydrochloric-acid solutions, but facilitated extinction of aversion to a sodium-chloride solution. These results do not support the general belief that ethanol retards extinction, but seem more consistent with the suggestion that IP injection of ethanol produces a taste which interacts with the tastes of orally ingested substances. Some implications of this possibility for the study of pharmacological agents on conditioned taste aversion are discussed.

Ethanol and avoidance-avoidance conflict in the rat

The effects of ethanol on avoidance-avoidance conflict behavior in a straight runway were studied in rats with a 2 by 2 design in which shock-escape training and subsequent shock-free conflict tests were administered after the animals had orally ingested either ethanol or sugar water. Rats trained under ethanol escaped shock more slowly and, during the conflict tests, approached the shock regions less closely, started and ran more slowly, and oscillated less than sugar-water-trained controls. However, rats tested under ethanol approached the shock regions more closely, started and ran more rapidly, oscillated more, and reversed direction more than rats tested when sober. No state-dependent interactions were obtained. Some of the results were consistent with a fear-reduction hypothesis, but others supported the assumption that ethanol affected the two avoidance gradients differentially.

Startbox-goalbox confinement durations as determinants of self-punitive behavior☆

Abstract Two levels of confinement duration (5 or 60 sec) in either startbox or goalbox were factorially combined with presence or absence of shock during extinction of a runway escape response in a self-punitive paradigm under a spaced-trials procedure. All groups were equated for amount and temporal spacing of handling before and after each trial. Shocked rats were more resistant to extinction than nonshocked rats only when startbox confinement was short. When startbox confinement was long, shock facilitated extinction. Long goalbox confinement enhanced running speed for shocked rats, but only in the presence of shock. It was suggested that duration of startbox confinement affects strength of conditioned fear, with long confinement leading to its extinction.

Ethanol and stimulus generalization

Two experiments examined stimulus generalization after injection of a dose of ethanol that did not affect motor performance (.8 g/kg). Generalization of conditioned suppression to tone frequencies was assessed in the first study with rats. In the second study, generalization of the pigeon’s autoshaped keypeck was examined along a line-tilt continuum. In both experiments, ethanol had no significant effect upon the height or shape of the generalization gradient. The second experiment also contained a dose-response analysis of keypecking in a hue-discrimination task. A low dose of ethanol (.4 g/kg) increased CS+ responding, a moderate dose (.8 g/kg) had no effect, and a high dose (1.2 g/kg) depressed responding. Responding to CS— was unaffected by any dose.