Behavioral neuroscience
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Behavioral neuroscience · Oct 1985
Differential changes in noradrenaline turnover in specific regions of rat brain produced by controllable and uncontrollable shocks.
A series of three studies was performed to investigate the effects of the ability to avoid or escape shock (controllability) and the lack of ability to do so (uncontrollability) on noradrenergic neurons in various brain regions of male Wistar rats. The levels of noradrenaline (NA) and its major metabolite, 3-methoxy-4-hydroxyphenylethyleneglycol sulfate (MHPG-SO4), in the hypothalamus, amygdala, thalamus, midbrain, hippocampus, cerebral cortex, pons plus medulla oblongata, and basal ganglia were measured fluorometrically. These studies indicated that after 3 hr and 6 hr in a free operant avoidance-escape stress procedure, the experimental rats able to avoid or escape shock showed greater increases in NA turnover (lower NA levels and higher MHPG-SO4 levels) in specific brain regions (i.e., the hypothalamus, amygdala, and thalamus) than the yoked rats unable to control the same shock. ⋯ Yoked rats given the same repetitive sessions of uncontrollable shock displayed sustained increases in NA turnover preferentially in the hypothalamus and amygdala, compared with the experimental rats. These results suggest that NA release in specific brain regions in the experimental "coping" rats is increased before the rats have learned the effective coping response. However, once a coping response is firmly established, NA release is reduced.
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Behavioral neuroscience · Aug 1985
Environmental influences on locomotor recovery following cortical lesions in rats.
Groups of rats were exposed to an enriched environment 2 hr per day for 30 days during the immediate pre- and/or postoperative period, or not at all. Animals in four of these groups sustained lesions in the bilateral sensorimotor cortex. One sham-operated control group was enriched pre- and postoperatively; a second control group was not. ⋯ Animals that were enriched preoperatively failed to demonstrate any deficit postoperatively, and the topology of their hindlimb movement appeared to be normal. In preoperatively impoverished animals, postoperative enrichment reduced the degree of initial deficit and speeded recovery of locomotion when compared with animals not enriched at all. However, preoperatively impoverished rats demonstrated an aberrant topology of hindlimb movement even after they were "behaviorally recovered".
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Behavioral neuroscience · Jun 1985
Comparative StudyNondependent monkeys self-administer hydromorphone.
Four monkeys, 2 rhesus and 2 cynomolgus, were trained to perform a multiple fixed-ratio extinction (MULT/FR/EXT) schedule for banana pellets. Subsequently, all animals were given hydromorphone (HYM) self-administration training, which consisted of substitution of FR (fixed ratio) 2 cocaine for FR 80 banana pellets and substitution of FR 2 HYM for FR 2 cocaine. All of the animals acquired cocaine self-administration. ⋯ Because none of the monkeys showed signs of spontaneous withdrawal or disruption of their appetitive baseline during the second postmaintenance session, a HYM challenge dose of 1 mg/kg was given noncontingently to assess whether tolerance to the daily maintenance dose had been acquired. The bolus dose of HYM suppressed lever pressing for food in both species, a result indicating a lack of tolerance. These results suggest that the positive reinforcing properties of HYM are sufficient to maintain opioid self-administration and that tolerance and physical dependence are not necessary.
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Behavioral neuroscience · Jun 1983
Self-administered intravenous infusion of hypertonic solutions and sodium appetite of sheep.
The effects of self-administered iv infusion of hypertonic NaCl, mannitol, glucose, urea, or isotonic NaCl on Na appetite were studied. Sodium-depleted sheep were trained to bar press in order to replace Na deficits of 300-500 mmol. During basal conditions, each delivery to a drinking cup was 15 ml of .6 M NaHCO3 (9 mmol). ⋯ Isotonic NaCl had no effect on the ingestion of NaHCO3 solution, plasma, or CSF composition. In regard to the "turn-off" of Na appetite by systemic infusion, these data are consistent with the theory of neural cells within the blood-brain barrier responsive to changes of Na concentration or osmolality in their environment. In contrast, water intake was stimulated by hypertonic NaCl or mannitol but not by urea or glucose, results suggestive that the sensors involved in thirst (e.g., osmoreceptors) are in an area of the brain lacking the blood-brain barrier.