Short- and long-term lithium administration: effects on the brain's serotonergic biosynthetic systems

Short-term treatment with lithium chloride stimulates the uptake of tryptophan and its conversion to serotonin by striate synaptosomes. Preincubation of striate synaptosomes with L-tryptophan and in vivo administration of L-tryptophan appear to act in a similar manner. Midbrain tryptophan hydroxylase activity is reduced in temporal continuity with the lithium-induced activation of tryptophan uptake and conversion. By 10 days, conversion of tryptophan to serotonin in nerve endings becomes a joint function of the maintained increased uptake of tryptophan and a decreased level of tryptophan hydroxylase activity in nerve endings. The occurrence of this delayed alteration corresponds in time to the previously described axoplasmic flow rate for tryptophan hydroxylase.     

Thyroxine: effects of neonatal administration on maturation, development, and behavior

In the report, "Thyroxine: effects of neonatal administration on maturation, development, and behavior," by S. Schapiro and R. J. Norman (10 Mar., p. 1279), the first line of Fig. 2 should read: "Fig. 2. Electroencephalograms from the cortex of thyroxine-treated and control infant...."     

Thyroxine: effects of neonatal administration on maturation, development, and behavior

Thyroxine was administered to infant rats within the first 3 days of postnatal life; controls receiving 0.01N NaOH were from the same litter. Thyroxine accelerated the maturation of the pituitary-adrenal response to elec tric shock. The "startle response" ap peared earlier in the experimental ani mals, as did the development and re sponse of the electroencephalogram to novel stimuli. The thyroxine-treated rats, when 16 to 18 days old, acquired a conditioned-avoidance response faster than did controls.     

Norepinephrine turnover and metabolism in rat brain after long-term administration of imipramine

The rate of disappearance of intracisternally administered tritiated norepinephrine from rat brain is decreased after a single dose of the tricyclic antidepressant imipramine. During long-term administration of imipramine, however, the rate of disappearance of tritiated norepinephrine from brain gradually increases, and there is a concurrent decrease in the content of endogenous norepinephrine in brain. These findings may help to explain why antidepressant effects are observed clinically only after long-termn treatment with imipramine.     

Monosodium glutamate: lack of effects on brain and reproductive function in rats

Monosodium glutamate was injected subcutaneously in infant rats of both sexes. The lateral preoptic and arcuate nuclei and median eminence were examined by light and electron microscopy for possible monosodium glutamate effects. As adults, treated animals showed no adverse monosodium glutamate effects on the reproductive system and neural morphology.     

冬季圈养灰雁行为初步观察

灰雁Anser anser是雁形目Anseriformes鸭科Anatidae雁属Anser的珍稀鸟类。为深入了解人工饲养灰雁冬季的行为节律,以东洞庭湖救助的灰雁为研究对象,利用目标动物取样法对灰雁冬季行为进行观察。研究将灰雁的行为分为取食、运动、警戒、静止、清理、社会共6类,包含20种具体行为,并对每一种行为进行了描述,建立了灰雁行为谱。记录灰雁每一种行为持续的时间。研究发现:灰雁不同行为最长持续时间差异较大,灰雁休憩行为最长可持续20 min左右,但通信的最长时间仅为16 s。灰雁不同行为的最短持续时间则差异不大,为3~10 s。白天行为节律的研究表明:取食、静止、运动、清理是灰雁冬季所占时间比例较高的行为,但各行为所占时间比例在1 d中存在波动。静止是灰雁行为所占比例最大的行为种类,主要发生在上午和傍晚,取食行为在1 d中存在2个高峰,但受喂食时间的影响。警戒主要伴随摄食而发生,且摄食时会伴随较多其他行为。冬季人工饲养灰雁白天行为节律的研究对于灰雁的成功救助和人工繁殖具有十分重要的意义。图 2 表 2 参16     

Object-carrying by rats: an approach to the behavior produced by brain stimulation

Rats were provided with opportunity to turn reinforcing hypothalamic stimulation on and off by traversing back and forth across a chamber. When provided with edible and inedible objects, all animals that self-stimulated carried them from the stimulation to the nonstimulation side. Neither food deprivation nor a history of stimulus-bound eating produced a preference for the edible objects. Equivalent stimulation provided without regard to the animals' location in the chamber did not elicit object-carrying. Results are interpreted in terms of the natural conditions which normally elicit this species-specific unit of behavior. Implications for understanding other behavior patterns elicited by hypothalamic stimulation are suggested.     

Growth hormone-releasing factor: direct effects on growth hormone, glucose, and behavior via the brain

Intracerebroventricular administration of human pancreatic growth hormone-releasing factor caused a dose-dependent inhibition of growth hormone secretion, elevated plasma glucose concentrations, and produced marked behavioral and motor effects. Immunoneutralization with antiserum to somatostatin did not reverse the suppression of growth hormone. These findings suggest that hypothalamic growth hormone-releasing factor may regulate its own neurosecretion through an "ultrashort-loop" negative feedback mechanism and may have important neurotransmitter and neuromodulatory functions in the brain.     

Microwaves: effect on thermoregulatory behavior in rats

Rats, with their fur clipped, pressed a lever to turn on an infrared lamp while in a cold chamber. When they were exposed to continuous-wave microwaves at 2450 megahertz for 15-minute periods, the rate at which they turned on the infrared lamp decreased as a function of the microwave power density, which ranged between 5 and 20 milliwatts per square centimeter. This result indicates that behaviorally significant levels of heating may occur at an exposure duration and intensities that do not produce measurable changes in many other behavioral measures or in colonic temperature. Further study of how microwaves affect thermoregulatory behavior may help us understand such phenomena as the reported "nonthermal" behavioral effects of microwaves.     

Weaning of young rats: effect of time on behavior

Male rats were weaned on the 15th, 16th, 17th, 25th, and 30th day of postnatal life. The rate of elaboration of the conditioned reflex at 8 months of age and the stability of the memory trace at 12 months were studied. Compared with rats weaned at 30 days of age, those weaned on day 15 elaborated the conditioned reflex much more slowly and the memory trace was less firm. Rats weaned on days 16 and 17 elaborated the conditioned reflex more quickly than rats weaned on day 15 but more slowly than those weaned on day 30. In all groups the memory trace showed the same stability and was significantly firmer than in rats weaned on day 15. The higher nervous activity of rats weaned at the age of 25 days more nearly resembles that of rats weaned at 15 days than the 30th day.     

Ribonucleic acid: effect on conditioned behavior in rats

Acquisition of a behavioral response motivated by shock was enhanced in rats chronically treated with yeast ribonucleic acid, and resistance to extinction was greater in rats so treated than in controls. This extends the role of ribonucleic acid to include a behavioral effect in laboratory mammals treated with a purified preparation from yeast.     

Tetrodotoxin: effects on brain metabolism in vitro

A 3-micromolar concentration of tetrodotoxin completely inhibits the stimulation of respiration of rat brain cortex that takes place upon application of electrical impulses. It also inhibits increase in the rate of the respiration that occurs when calcium ions are omitted from the incubation medium. No effect of tetrodotoxin on brain respiration takes place when stimulation is brought about by the addition of 100 millimolar potassium chloride. Tetrodotoxin prevents the fall in the rate of oxidation of cerebral acetate that occurs during electrical stimulation but does not affect the increased rate of the oxidation that occurs in the presence of an increased concentration of potassium chloride. The data indicate that oxidation of cerebral acetate is diminished by influx of sodium ions, which is prevented by tetrodotoxin, and is increased by influx of potassium ions, which is unaffected by tetrodotoxin.     

Electroshock effects on brain protein synthesis: relation to brain seizures and retrograde amnesia

The effects of electroshock on brain seizure activity and brain protein synthesis were studied in male mice. A significant but short-lasting inhibition of brain protein synthesis and an increase in the amount of free leucine were produced by electroshock at intensities above the brain seizure threshold. Electroshock at intensities below the brain seizure threshold did not affect brain protein synthesis.     

Following the crowd: brain substrates of long-term memory conformity

Human memory is strikingly susceptible to social influences, yet we know little about the underlying mechanisms. We examined how socially induced memory errors are generated in the brain by studying the memory of individuals exposed to recollections of others. Participants exhibited a strong tendency to conform to erroneous recollections of the group, producing both long-lasting and temporary errors, even when their initial memory was strong and accurate. Functional brain imaging revealed that social influence modified the neuronal representation of memory. Specifically, a particular brain signature of enhanced amygdala activity and enhanced amygdala-hippocampus connectivity predicted long-lasting but not temporary memory alterations. Our findings reveal how social manipulation can alter memory and extend the known functions of the amygdala to encompass socially mediated memory distortions.