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At least 991 records · Page 55Linked to original sources
PubMed1976

Disinhibition and external inhibition of response following septal lesions in rats.

Septal-lesioned and sham-operate rats were tested for reactivity to extraneous stimuli (clicks or flashing lights) presented during periods of low or high responding generated by a 120-sec FI schedule of reinforcement. While septal-lesioned rats tended to show greater disinhibition and less external inhibition than sham-operates, the magnitude of the deficits was not considered sufficiently great to warrant the conclusion that the septal syndrome results from increased susceptibility to disinhibition.

Acoustic Stimulation↗
PubMed1984

Subject control as a determinant of the reinforcing properties of intracranial stimulation.

There has been some controversy whether experimenter-administered electrical stimulation of the brain is aversive or simply less reinforcing than that delivered via self-stimulation. Rats with MFB-LH electrodes self-stimulated with high, medium, and low currents and the self-produced rates were tape recorded. In Experiment 1, the rats were allowed to choose between self-administered versus replayed ESB. When both types of stimulation were available at medium intensities, the rats preferred to self-administer the ESB. This preference was increased when the re-played stimulation was presented at a lower intensity than the self-administered ESB. However, the preference for contingent ESB decreased when the intensity of the experimenter administered ESB was increased suggesting that experimenter-administered ESB is not aversive. In Experiment 2, the rats chose between experimenter administered ESB delivered at the played-back self-generated rate versus a regular averaged rate. All Ss preferred the previously self-generated mode. In Experiment 3, the rats were deprived of water and given four daily competition tests between experimenter administered ESB versus water. All rats "self-dehydrated" again demonstrating that experimenter-administered ESB is not aversive. It is concluded that rats prefer to control the rate at which ESB is presented, but that non-contingent stimulation is clearly not aversive.

Animals↗
PubMed1986

Clonidine has a bidirectional effect on operant responding for food.

Clonidine, an alpha-noradrenergic agonist, has had inconsistent effects when administered peripherally in previous studies of feeding behavior. The present experiment was undertaken to evaluate clonidine using an operant feeding paradigm (continuous reinforcement schedule) to provide detailed data on the time course of its effects. Over an entire four-hour session, all doses of clonidine tested (25, 50, or 100 micrograms/kg) increased bar-pressing. The 50 micrograms/kg dose was most effective. An examination of the time course of responding revealed that the initial effect of clonidine was to decrease responses with the duration and magnitude of the decrease directly proportional to dose. However, clonidine also prolonged a phase of steady responding for food once the animals resumed bar-pressing, resulting in a net increase of food intake. Future investigations of clonidine should take into account the effects of increasing dose on delayed onset of feeding.

Animals↗
PubMed1987

Effects of medial frontal cortex lesions on DRL performance in rats.

Rats with medial frontal cortical lesions (MFC) and control animals with sham operations were tested on an ascending series of 8 DRL schedules of reinforcement ranging from 5 to 70 seconds. Rats with MFC lesions did not differ from the control group in performance when response rate, responses per reinforcement and efficiency were analyzed. These results indicate that deficits in "response inhibition" often displayed by rats with MFC lesions may be task-specific.

Animals↗
PubMed1990

Predictability of repeated challenge: effects on cardiovascular activity in the type A (coronary prone) behavior pattern.

Fifty-two healthy young adults classified either as Type A (coronary prone) or Type B were randomly assigned to a vigilance task during which observing responses produced targets according to either a predictable (i.e., fixed-interval 90-sec) or a nonpredictable (i.e., random-interval 90-sec) reinforcement schedule. During the task, blood volume pulse, interbeat interval, masseter (EMG) activity, and blood pressure were monitored. Transient peripheral vasomotor constriction and heart rate increases were initiated within an 8- to 12-sec period following target detection with the predictable schedule, with subjects evincing greater responsivity than their nonpredictable schedule counterparts. Type A subjects assigned to the random-schedule evinced significantly shorter heart rate and blood volume pulse response durations than did Type B subjects. Longer postevent EMG elevations were evidenced by subjects assigned to the predictable schedule. No significant blood pressure differences were found among the groups. The impact of challenge-contingent behavior on cardiovascular responsivity and the relevance of attentional processes to this relationship and to cardiovascular risk are discussed.

Adult↗
PubMed1993

Spontaneously hypertensive rats (SHR) as a putative animal model of childhood hyperkinesis: SHR behavior compared to four other rat strains.

Childhood hyperkinesis or attention-deficit hyperactivity disorder (ADHD) is a behavior disorder of which the main symptoms are attention problems and hyperactivity. The main objective of the present study was to investigate whether the spontaneously hypertensive rat (SHR) strain is a useful animal model of ADHD. Five different rat strains were tested: SHR, Wistar-Kyoto (WKY), Wistar, Sprague-Dawley (SPRD), and PVG (hooded) rats. The protocol consisted of three different test procedures: 1) A 7.5-min free-exploration open-field test (home cage accessible), where the SHR was less active than Wistar and SPRD but more active than WKY; SHR showed longer latencies to leave the home cage than both Wistar and SPRD rats, spending less time in the field, ambulating and rearing less than Wistar and SPRD but more than WKY. Within session, the SHR tended to be more active at the end of the session than at the start, while the opposite tended to be the case in the other groups. 2) A 7.5-min forced exploration open-field test (home cage not accessible), where the results showed that the SHR is less active than both the Wistar and Sprague-Dawley strains, but more active than PVG and WKY. 3) A two-component multiple schedule of reinforcement with a fixed interval 2 min signalled by houselight on and a 5-min extinction signalled by houselight off. Lever pressing by SHR was markedly different from that of the other four strains, which were quite Except early in the interval, SHR pressed the lever more than any of the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Interactions between atropine, chlorpromazine and cocaine on food reinforced behavior.

Previous investigations have demonstrated the ability of atropine and chlorpromazine pretreatment to increase intravenous cocaine self-administration in rhesus monkeys. These results were interpreted as resulting from either an antagonism of cocaine's reinforcing effect or an effect of cocaine which may interfere with its self-administration. The generality of the postulated drug antagonism was tested in monkeys exhibiting stable FR10 food-reinforced behavior. Intramuscular pretreatment with 0.25-4.0 mg/kg of chlorpromazine significantly depressed this behavior as did pretreatment with 0.25-2.0 mg/kg of atropine. These same dosages had been shown to increase cocaine self-administration. Fifteen-minute influsions of cocaine (1.0-10 mg/kg), which began 15 min after session onset, also resulted in a depression of food reinforced behavior. When chlorpromazine pretreatment and cocaine infusion were combined, the decrement in food reinforced responding was lessened. However, when cocaine infusion and atropine pretreatment occurred concurrently, the depression in responding was increased. These data indicate that chlorpromazine may nonspecifically antagonize the behavioral effects of cocaine; whereas, atropine may enhance these effects.

Animals↗
PubMedDate not supplied

LSD and fixed-internal responding in the rat.

A series of 6 doses of lysergic acid diethylamide-25 (LSD) altered the bar-pressing behavior of 6 rats maintained on a fixed-interval, 5 min (FI 5) schedule of reinforcement. High doses of LSD (0.16, 0.32 mg/kg) depressed overall rates of responding. Low response rates, which occurred during the first half of the interval between successive reinforcements, were increased by low (0.01, 0.02 mg/kg), moderate (0.04, 0.08 mg/kg), and high doses of LSD; high rates of responding which occurred during the final half of the interval were decreased only by high doses of LSD. All doses (except the lowest) decreased the Index of Curvature, a statistic describing the temporal distribution of responses. The results were discussed in terms of baseline rate of responding and the presence or absence of timing behavior.

Animals↗
PubMed1976

Ethanol as a positive reinforcer via the oral route for rhesus monkeys: maintenance of fixed-ratio responding.

Two rhesus monkeys were required to emit 1 to 16 responses (FR 1, 2, 4, 8, and 16) per 0.5 ml delivery of either 8% (w/v( ethanol or water. Ethanol had been established as an effective reinforcer via the oral route in an earlier experiment [4]. At FR 16, responding maintained by ethanol clearly exceeded responding maintained by water for both monkeys. The volume of ethanol intake per session remained nearly constant from FR 1 to FR 16, however, the volume of water consumed per session decreased when FR 16 was required.

Animals↗