Search PubMed⌕ Search

Biomedical subjects

J R Nation

Publications and source records attributed to J R Nation.

54 records · Page 3Linked to original sources
PubMed1983

Behavioral effects of chronic lead exposure in the adult rat.

Adult rats fed daily rations of laboratory chow laced with lead acetate, were tested for operant (schedule-controlled) responding and conditioned suppression. In Experiment 1, animals receiving 10 mg/kg lead showed significantly lower operant response rates (lever pressing) than controls. Conditioned suppression performance was not different between the two groups. During retraining that followed a 42 day no-training period, lead-treated subjects showed greater percent of prior baseline responding than controls. The groups were not different on a test for stimulus control or an appetitive resistance to extinction test. In Experiment 2, separate lead-treated groups were chronically exposed to either 10 mg/kg, 5 mg/kg, or 1 mg/kg lead daily. Behavioral tests showed that while the lowest lead level (1 mg/kg) occasioned higher rates of operant lever pressing relative to controls, the highest level (10 mg/kg) again produced lower rates. On a retraining task administered after an interpolated 90 day no-training period, the two highest exposure groups were significantly above controls regarding percent of baseline responding and there was evidence that the 5 mg/kg group was significantly superior to controls in terms of absolute response rate. No differences in conditioned suppression or resistance to extinction were observed in the second experiment.

Animals↗
PubMed1982

Conditioned suppression in the adult rat following chronic exposure to lead.

Conditioned suppression was examined for control (N = 8) and lead-treated (N = 8) adult rats. Treated animals were exposed daily to 10 mg/kg lead administered via the diet as lead acetate. 40 days of operant lever press training on a multiple schedule using food as reward was given. Lever press training continued for an additional 5 days but during this period subjects experienced superimposed 3 min tone presentations followed by electric shock (1.3 mA, 1.5 s duration) to a grid floor. Tone presentations were observed to be significantly more disruptive of operant steady state responding for treated subjects as compared to controls. This finding supports earlier claims that lead exposure enhances emotionality.

Animals↗
PubMed1980

Persistence: the role of partial reinforcement in psychotherapy.

Persistence, which refers to the ability of a learned behavior to survive protracted nonreinforcement (extinction), has been an overlooked dimension of clinical intervention. While persistence of newly acquired coping behavior is desired (and possibly assumed) by all psychotherapeutic procedures, few treatment programs possess features that operate to sustain responding in the face of a nonsupportive, nonreinforcing environment. The present article presents a treatment strategy designed to foster persistence based on the laboratory findings that partial reinforcement schedules produce greater resistance to extinction than continuous reinforcement schedules--a phenomenon referred to as the partial reinforcement extinction effect. The two major theories of persistence (Amsel's general theory of persistence and Capaldi's sequential theory) are discussed, and the basic principles of these models are extended to a number of therapeutic modalities including depression therapies, systemic desensitization, assertiveness training, and aversion therapy. In addition, procedural considerations including generalized and discriminated persistence are discussed.

Adaptation, Psychological↗
PubMed1978

Persistence training: a partial reinforcement procedure for reversing learned helplessness and depression.

This article examines the relative merits of either partial or continuous (total) success therapy as a device for reversing learned helplessness and depression in humans. College students experienced (a) no treatment followed by either abbreviated (20 trials) or extended (40 trials) continuous success therapy, (b) soluble problems followed by either abbreviated or extended continuous success therapy, (c) insoluble problems followed by either abbreviated or extended continuous success therapy, or (d) insoluble problems followed be either abbreviated or extended partial success therapy. Subsequently, subjects in all eight groups received 40 escape-extinction trials in which aversive tones were not controllable. The results of this experiment indicated that both continuous and partial success schedules were effective in reversing depressed responding (helplessness) induced by prior exposure to insoluble problems. However, only the partial success therapy schedules produced persistent escape responding in extinction. Also, across therapy procedures, extended therapy generated more response persistence in escape extinction than did abbreviated therapy. Theoretical implications of these results are discussed, and a compatible new treatment program, labeled persistence training, is introduced.

Adolescent↗
PubMedDate not supplied

Cadmium exposure results in decreased responsiveness to ethanol.

Adult male Sprague-Dawley rats were maintained on an ad lib diet containing 100 ppm cadmium (Group Cadmium-Diet) or a control diet with no added cadmium. On Day 61, all animals (N = 10/group) were challenged with a single hypnotic dose of ethanol (3.5 g/kg IP), prepared from a 20% v/v solution of tap water and a stock solution of 95% ethanol. The latency from the time of the injection until the loss of the righting reflex was recorded, as well as the latency for recovery of the reflex. The results showed a nonsignificant trend for animals exposed to cadmium to lose the righting reflex less rapidly than controls, and Cadmium-Diet animals regained the righting reflex significantly more rapidly than controls. These findings suggest that the pharmacologic effectiveness of ethanol is altered by chronic exposure to dietary cadmium. The implications of these data for other studies of cadmium/ethanol interactions are discussed.

Animals↗
PubMedDate not supplied

The effects of naltrexone on cadmium-induced increases in oral ethanol self-administration.

Adult male rats were exposed to a standard laboratory diet (N = 20), or an adulterated diet containing 100 ppm added cadmium (N = 20), for 60 days. On Day 61, half the animals from each dietary condition received subcutaneous implants of two 30 mg naltrexone pellets, and the remaining half the animals received identical implants of 30 mg placebo pellets. One week later, animals from groups created by this interaction (Groups Control-Placebo, Control-Naltrexone, Cadmium-Placebo, Cadmium-Naltrexone) were tested in an ethanol self-administration paradigm that presented a 10% ethanol solution (v/v) in both a choice and nonchoice format. The results indicated that cadmium exposure increased the oral self-administration of ethanol in the choice setting where water was offered as an alternative, and the opiate antagonist naltrexone failed to attenuate this effect.

Alcohol Drinking↗
PubMedDate not supplied

Lead attenuates the antipunishment effects of ethanol.

Adult male rats were exposed to a diet containing no added chemicals, or a diet containing 500 ppm added lead (as lead acetate), for 70 days. On Day 71 (training day), after 24 h of water deprivation, all animals were placed in a test apparatus and permitted to make 220 licks for a 5.5 percent (v/v) sucrose in water solution. On Day 72 (test day), all animals received conditioned punishment training where electric shock was delivered to the tongue following every 20 licks of the sucrose and water solution. Prior to commencing punishment training on Day 72, half the animals for the control diet condition (Group Control-Diet-Saline), and half the animals for the lead diet condition (Group Lead-Diet-Saline), received IP injections of saline. Conversely, the remaining half of the animals (Groups Control-Diet-Ethanol and Lead-Diet-Ethanol) received IP injections of 1.5 g/kg ethanol. The results of the conditioned punishment test revealed that animals exposed to a control diet and administered ethanol (Group Control-Diet-Ethanol) engaged in more punished licking and received more shocks than their lead-treated counterparts (Group Lead-Diet-Ethanol). Both of the groups exhibited more punished licking and received more shocks than either of the groups that received saline injections. The possibility that lead contamination may reduce the pharmacologic impact of ethanol is noted.

Animals↗
PubMedDate not supplied

Lead/ethanol interactions. I: rate-depressant effects.

Adult male rats were exposed to a diet containing 500 ppm added lead as lead acetate (group lead-diet) or a control diet containing no added chemicals (group control-diet) for 61 days prior to commencing fixed-ratio 32 (FR 32) lever press training for water reinforcement. After steady state responding was achieved, all animals received serial administrations of acute doses of ethanol prior to the daily training session. Specifically, lead-diet and control-diet rats received i.p. injections of .25, .5, .75, 1.0, and 1.25 g/kg ethanol, in ascending order, alternating daily with injections of saline. The results revealed a dose-dependent rate-depressant effect, with higher doses of ethanol producing more behavioral suppression than lower doses for both groups. In addition, at the dose of 1.0 g/kg it was observed that the suppressive effects of ethanol on schedule-controlled responding were reduced among lead-treated animals relative to controls. These data are discussed in terms of lead-induced attenuation of the pharmacologic effects of ethanol.

Animals↗
PubMedDate not supplied

Lead/ethanol interactions. II: pharmacokinetics.

Adult male rats were exposed ad libitum to water containing either 500 ppm lead acetate (group-lead) or an equivalent amount of sodium acetate (group-control) for 60 days prior to receiving ip injections of either 1.0, 2.0, or 3.0 g/kg ethanol (20% v/v). Blood alcohol concentrations (BACs) were recorded over a 6-h time period postinjection, and the groups were compared at each dose for differences in the pattern of ethanol pharmacokinetics. While there was a dose-related effect obtained with increasing ethanol doses producing increasing BAC values, at no dose was there any evidence of group separation at any point during the 6-h postinjection period. These data are instructive with respect to understanding the nature of previously demonstrated lead/ethanol interactions, and rule out the possibility that lead-induced disturbances in the catalysis of ethanol, or some other pharmacokinetic operation, is the basis for the effects of lead on ethanol intake and ethanol administration. Alternative possible accounts of this curious interaction between a xenobiotic contaminant and alcohol are discussed.

Animals↗
PubMedDate not supplied

Ethanol self-administration in rats following exposure to dietary cadmium.

Rats were maintained on an ad lib diet containing 100 ppm cadmium (Group Cadmium-Diet) or a control diet with no added cadmium (Group Control-Diet). After 55 days of exposure to their respective diets, animals were tested for fluid intake using a nonchoice procedure that presented a 15% ethanol solution in the home cage for 5 days. Subsequently, all animals were offered a 10% ethanol solution or tap water in a 3-bottle, 2-fluid choice test in the home cage. This fluid intake test was conducted for a 5 day baseline period, and then again concurrently with avoidance acquisition (14 days) and extinction (4 days) training on a free operant (Sidman) avoidance task that required animals to lever press to avoid electric footshock. After training was terminated the choice test was continued further in the home cage for a 15 day post-avoidance period. Ethanol intake was greater for animals exposed to cadmium on all tests of fluid consumption, and all animals consumed more ethanol during the periods following termination of the stressor (avoidance extinction, post-avoidance) than during the actual period of stress (avoidance acquisition). Interpretive comments focus on the effects of cadmium on stress reactivity, sensory processing, and metabolism.

Alcohol Drinking↗
PubMedDate not supplied

The effects of cadmium on the self-administration of ethanol and an isocaloric/isohedonic equivalent.

During a period of baseline fluid intake recording, adult male rats were presented with a three-bottle, two-fluid choice test that offered either a 10% ethanol solution (v/v) and tap water as alternatives, or a sucrose/quinine solution and tap water as alternatives. The sucrose/quinine solution was equivalent to the ethanol solution both in terms of calories and palatability. After intakes stabilized, half of the animals from each test condition were placed on a diet containing 100 ppm cadmium and the remaining half of the animals were placed on a standard laboratory diet. After 60 days of exposure to their respective diets, all animals were presented their earlier test solutions, both in a nonchoice and choice format. The results from the choice test indicated that although cadmium treatment did not produce a clear preference for ethanol over water, cadmium exposure was associated with a significant increase in ethanol consumption. Moreover, the self-administration of the isocaloric/isohedonic equivalent (sucrose/quinine solution) was unaffected by cadmium contamination. These data are discussed in terms of their implications for both nutritional and sensory-impairment accounts of metal-related changes in the volitional intake of ethanol.

Alcohol Drinking↗
PubMedDate not supplied

Behavioral antagonism between lead and cadmium.

Adult male rats were exposed to one of four dietary conditions for a period of 60 days. Group Control-Diet received a diet containing no added lead or cadmium, group Lead-Diet received a diet that contained 500 ppm added lead, group Cadmium-Diet received a diet that contained 100 ppm added cadmium, and group Lead-Cadmium-Diet received a diet that contained both 500 ppm added lead and 100 ppm added cadmium. Subsequent to exposure, animals were tested in a Digiscan activity monitor. Animals were then sacrificed and metal concentrations were determined in blood and brain. The results from this experiment showed that lead alone increased movement and vertical activity. Cadmium alone decreased movement and increased rest time. Cotreatment with lead and cadmium failed to produce behavioral differences relative to controls; thus, it seems that the changes in activity caused by one metal are antagonized by the other. Results from the analyses of residues in tissues revealed that blood lead concentrations were lower in the cotreatment condition than the lead along condition. However, brain residue accumulations were not different for these two exposure conditions. There was no evidence that the presence of lead attenuated increases in cadmium residues in blood or brain. Overall, the residue data agree with a central, as contrasted with a peripheral, account of lead/cadmium interaction effects, at least as relates to behavior. Because lead and cadmium were additive with regard to producing decreased body weights, it seems that the toxic effect of these metals is antagonized by cotreatment in some instances, and augmented in others.

Animals↗
PubMedDate not supplied

The effects of chronic cobalt exposure on behavior and metallothionein levels in the adult rat.

Adult rats fed daily rations of laboratory chow laced with cobalt chloride were tested for operant (schedule-controlled) responding and conditioned suppression (CER). Animals exposed to 20 mg/kg Co, but not animals exposed to 5 mg/kg Co, lever pressed at a significantly slower rate than nontreated control subjects over the last 8 sessions of a 35 session operant training phase (1 session/day). Control and treatment subjects did not show significantly different CER performances. Nor were significant differences found on a test of mixed VI-2, DRO responding where subjects were required to lever press for reward during the first 15 min component and not lever press during the last 15 min component of the schedule. Testicular atrophy was evident among subjects exposed to 20 mg/kg Co. Atomic absorption spectrophotometric analyses revealed a dose-response effect regarding tissue accumulations of Co in blood, bone, brain, hair, small intestine, kidney, liver, and testes. Contrary to the biochemical pattern shown by some other heavy metals, prolonged Co exposure did not induce significant increases in metallothionein concentrations in the liver, kidney, or small intestine.

Animals↗
PubMedDate not supplied

The effects of chronic cadmium exposure on schedule controlled responding and conditioned suppression in the adult rat.

Adult rats fed daily rations of laboratory chow with added CdCl2 were tested for schedule controlled responding and conditioned suppression (conditioned emotional response-CER). Determinations of tissue Cd, levels of metallothionein, and the ratio of Cd in the tissue to the Cd-binding capacity of metallothionein also were made. Animals were exposed daily to either 5 mg/kg Cd (Group Cd-5), 1 mg/kg Cd (Group Cd-1), or no Cd (Group Control). An initial phase of training on a variable interval 2 min (VI-2) food reinforcement schedule lasting 40 sessions (1 session/day) was followed by CER training and then an interpolated period (100 days) of continued exposure but with no training. Schedule retraining was introduced for 21 sessions (1 session/day). The results showed no group differences during original schedule training. On the CER test, Group Cd-1 was found to exhibit less suppression (defined in terms of lever press rates) than controls to preaversive stimuli. Group Cd-5 showed significantly greater suppression to the primary aversive stimulus (shock) than the other two groups. Both treatment groups showed significantly lower lever press rates than controls on the schedule retraining task. These behavioral disturbances occurred commensurate with increases in non-metallothionein bound Cd in the liver, kidney, and small intestine.

Animals↗