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K C Liang

Publications and source records attributed to K C Liang.

46 records · Page 3Linked to original sources
PubMed1983

4-OH amphetamine enhances retention of an active avoidance response in rats and decreases regional brain concentrations of norepinephrine and dopamine.

An .82 mg/kg dose of dl-4-OH amphetamine administered ip immediately following training in a one-way active avoidance task enhanced retention performance measured 24 hr later. In contrast, 4-OH amphetamine in a dose range of .41--1.65 mg/kg ip did not affect retention of a swim escape task. The behaviorally active dose of .82 mg/kg 4-OH amphetamine decreased dopamine concentrations in the amygdala and hippocampus. A dose of 8.2 mg/kg 4-OH amphetamine administered ip to naive untrained rats decreased concentrations of norepinephrine measured in the amygdala, cortex, hippocampus, hypothalamus, and midbrain; decreased concentrations of dopamine in the amygdala, cortex, hippocampus, and striatum; and significantly reduced concentrations of norepinephrine and epinephrine in the adrenal medulla. In addition, because the integrity of the adrenal medulla is necessary for the enhancing action of 4-OH amphetamine and because 4-OH amphetamine reduces concentrations of catecholamines in the brain and adrenal medulla, it is possible that 4-OH amphetamine affects retention performance by a dual action on the brain and the adrenal medulla.

Adrenal Medulla↗
PubMed1982

Post-training amygdaloid lesions impair retention of an inhibitory avoidance response.

The study examined the effect of pre- and post-training bilateral amygdaloid lesions on retention of a one-trial inhibitory avoidance response. Groups of rats, including unimplanted controls and implanted controls, were trained and tested for retention at 4, 7 or 12 days following training. The lesions were made at one of several intervals before or after training: 2 days before, immediately after, or 2, 5 or 10 days after. At all retention intervals the retention of implanted controls was poorer than that of unimplanted controls and, in comparison with both control groups, the retention of animals lesioned before training was impaired. Retention was also impaired by the post-training lesions. The degree of impairment varied with the interval between the training and the lesion: lesions made within 2 days following training impaired retention, while lesions made 10 days following training had no impairing effect. These findings suggest that post-training lesions of the amygdala affect retention by impairing time-dependent processes involved in memory storage. With a sufficiently long training-lesion interval (10 days) an intact amygdala is not essential for retention.

Amygdala↗
PubMed1981

Age-related changes in the catecholamine content of peripheral organs in male and female F344 rats.

Norepinephrine levels of old and young F344 rats of both sexes were compared in several organs that receive sympathetic innervation. In addition, both norepinephrine and epinephrine concentrations in the adrenal medulla of young and old rats were determined. A rationale was developed for making age-related comparisons of the catecholamine content in peripheral organs which accounted for age-related changes in organ weight and body weight. It was found that norepinephrine concentrations were decreased for old male rats in heart auricles. In contrast, in old female rats there were no age-related changes in the catecholamine content of any peripheral organ.

Adrenal Glands↗
PubMed1980

Attenuation of amphetamine-induced enhancement of learning by adrenal demedullation.

These experiments investigated the effect of immediate posttrial administration of peripherally acting DL-4-hydroxyamphetamine on retention of a one-trial inhibitory avoidance response in intact, adrenal medullectomized, sympathectomized, and medullectomized and sympathectomized rats. In intact rats, 0.82 mg/kg of DL-4-OH-amphetamine enhanced retention performance. In rats sympathectomized by peripheral 6-hydroxydopamine, 24 h prior to training, a lower dose of 4-OH-amphetamine (0.21 mg/kg) was most effective in enhancing retention. Adrenal demedullation abolished the memory enhancing effects of DL-4-OH-amphetamine and also D-amphetamine. These findings suggest that the memory enhancing effects of DL-4-OH-amphetamine and D-amphetamine involve adrenal medullary catecholamines.

Adrenal Medulla↗
PubMed1980

Central and peripheral actions of amphetamine on memory storage.

These experiments investigated the effects of central (intracerebroventricular) and peripheral (i.p.) posttraining administration of D-amphetamine on rat's retention of a one-trial inhibitory avoidance response. While retention was enhanced by i.p. administration (1.0 mg/kg) the central administration (dose range 50-500 microgram) did not affect retention. In rats given peripheral 6-OHDA 24 h prior to training a lower dose (i.p.) of amphetamine (0.25 mg/kg) was most effective in enhancing retention. These findings suggest that the mrmory enhancing effects of D-amphetamine are mediated at least in part through peripheral systems.

Animals↗
PubMed1980

Enkephalin and fear-motivated behavior.

Leu[Enkephalin (400.0 micrograms/kg) and the enkephalin analog [DAla,DLeu]enkephalin (0.4, 4.0, and 40.0 micrograms/kg) were intraperitoneally administered to rats 5 min before they were trained on aversively motivated tasks. The peptides impaired acquisition of a one-way active avoidance response, facilitated acquisition of an inhibitory avoidance response, and had no effect on acquisition of a swim-escape response. The data indicate that the enkephalin effects are not mediated through actions on locomotor activity, pain perception or reactivity, or light sensitivity. Rather, we suggest that [Leu]enkephalin and its analog strengthen the tendency of rats to suppress behavior in the presence of cues previously associated with aversive stimulation. This effect may be due to an enkephalin-induced increase in fear or arousal. The enkephalin effect on behavior was obtained at low doses and was observed within a few minutes after administration. These findings are consistent with the interpretation that enkephalin effects may be initiated at a peripheral site.

Animals↗
PubMed1975

The priority of malaria eradication programs.

The planning of health activities begins with the setting of priorities--that is to say, the selection and arrangement of the problems to be attacked in an order consistent with their gravity and the possibilities that exist for the adoption of effective measures for their soultion. The assignment of priorities not only implies financial, administrative, and manpower support, but also involves the continuing renewal of health workers' interest in fulfilling the tasks that have been entrusted to them. According to the extent and severity of the problem, priorities may have to be envisaged on a world, continental, regional, or local scale. Ever since the beginning of the present century the Governments of the Americas have accorded high priority to malaria control and, since 1954, to its eradication. In recent years malaria programs in the Americas have been classified into three groups according to their epidemiologic status and prospects for the future. As of 1974, Group I included the 12 political units (countries or territories) in which malaria had been eradicated. These units should give suitable priority to activities for ensuring that they remain free of the disease. Group II was composed of eight units whose prospects of achieving eradication within a short period were good. Here the highest priority should go to efforts designed to eliminate residual foci and to complete the last steps toward ultimate eradication. Group III contained 14 units, the majority of which had part of their territories in the consolidation or maintenance phase. In some of these Group III units malaria eradication could be achieved within a short period if additional funds are found; in others the situation is quite different and eradication cannot be expected in a foreseeable time. The latter units should therefore give high priority to activities that will conserve the gains already made (in those areas which are in the consolidation and maintenance phases) and that will gradually reduce the incidence of malaria in areas that are still in the attack phase. In general, when a malaria program is given high priority by the Government concerned, adequate funds for the campaign can be obtained more redily, either through the regular budget or from international and bilateral agencies.

Central America↗