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Biomedical subjects

T E Robinson

Publications and source records attributed to T E Robinson.

At least 109 records · Page 6Linked to original sources
PubMed1984

Sex differences in the effects of early experience on the development of behavioral and brain asymmetries in rats.

The influence of early experience (preweaning handling) on the development of several postural/motor asymmetries (side bias in an open field, turn preference in a T-maze, amphetamine-induced rotational behavior, tail pinch-induced asymmetries) and the lateralization of brain dopamine was studied in adult male and female rats. In many cases the adult patterns of behavioral and brain asymmetries were modified by early handling in a sexually dimorphic manner. In addition, the direction of postural/motor asymmetries was very much task-dependent, especially in females. We conclude that: early experience may modify the development of behavioral and brain asymmetries; sex differences in asymmetries are very common; early handling may affect males and females differently; and different measures of postural/motor asymmetries may reflect different and multiple brain asymmetries.

Animals↗
PubMed1984

A simple in vitro technique to measure the release of endogenous dopamine and dihydroxyphenylacetic acid from striatal tissue using high performance liquid chromatography with electrochemical detection.

An easily constructed, inexpensive and simple system is described for the superfusion of neural tissue. To characterize the system, the dynamics of endogenous dopamine and dihydroxyphenylacetic acid release from striatal tissue were studied before and after exposure to potassium, amphetamine or cocaine.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1983

Optimizing the exercise protocol for cardiopulmonary assessment.

Twelve normal men performed 1-min incremental exercise tests to exhaustion in approximately 10 min on both treadmill and cycle ergometer. The maximal O2 uptake (VO2 max) and anaerobic threshold (AT) were higher (6 and 13%, respectively) on the treadmill than the cycle; the AT was reached at about 50% of VO2 max on both ergometers. Maximal CO2 output, heart rate, and O2 pulse were also slightly, but significantly higher on the treadmill. Maximal ventilation, gas exchange ratio, and ventilatory equivalents for O2 and CO2 for both forms of exercise were not significantly different. To determine the optimum exercise test for both treadmill and cycle, we exercised five of the subjects at various work rate increments on both ergometers in a randomized design. The treadmill increments were 0.8, 1.7, 2.5, and 4.2%/min at a constant speed of 3.4 mph, and 1.7 and 4.2%/min at 4.5 mph. Cycle increments were 15, 30, and 60 W/min. The VO2 max was significantly higher on tests where the increment magnitude was large enough to induce test durations of 8-17 min, but the AT was independent of test duration. Thus, for evaluating cardiopulmonary function with incremental exercise testing by either treadmill or cycle, we suggest selecting a work rate increment to bring the subject to the limit of his tolerance in about 10 min.

Adult↗
PubMed1982

Long-term facilitation of amphetamine-induced rotational behavior and striatal dopamine release produced by a single exposure to amphetamine: sex differences.

Amphetamine (AMPH)-induced rotational behavior in non-lesioned rats and AMPH-stimulated dopamine (DA) release from striatal tissue fragments in vitro were used to study the long-term effects of a single injection of AMPH on activity in the mesostriatal DA system. A single injection of a low dose of AMPH (1.25 mg/kg) greatly enhanced the rotational behavior produced by a second injection of AMPH given 3-4 weeks later in intact female, ovariectomized female and castrated male rats. The effect of AMPH pretreatment in intact males differed from that in the other groups. When only 7-8 days separated the two test sessions both intact male and female rats showed sensitization of rotational behavior, but the magnitude of the change was greater in females. In addition, a single injection of 1.25 mg/kg of AMPH in vivo produced a long-lasting (3-5 weeks) enhancement of AMPH-stimulated DA release from striatal tissue in vitro. It is suggested that: (1) repeated injections of AMPH are not necessary to produce a long-lasting facilitation of behaviors mediated by the mesostriatal DA system; (2) gender and/or hormonal state influences the development of long-term changes in the mesostriatal DA system; and (3) changes in DA release from presynaptic terminals may contribute to the behavioral sensitization produced by stimulant drugs. The phenomena reported here may provide complementary in vitro and in vivo models for studying neuroplasticity in brain DA systems.

Animals↗
PubMed1982

Sex differences and estrous cycle variations in amphetamine-elicited rotational behavior.

The experiments reported here were designed to determine if there are sex- and/or estrus cycle-dependent differences in amphetamine (AMPH)-elicited rotational behavior in unlesioned rats. Whole brain or striatal levels of AMPH produced by systemic administration of the drug were also measured. At all doses tested (1.0-10.0 mg/kg) systemic administration of AMPH resulted in significantly higher brain levels of AMPH in females than in males. A systemic dose was then calculated which produced equivalent brain levels of AMPH in males and females. Even with equivalent brain levels of AMPH, males produced significantly fewer net rotations than females in estrus, diestrus 2, or proestrus. In female rats the brain levels of AMPH produced by systemic administration did not vary with the estrous cycle. However, the amount of AMPH-elicited rotational behavior did. On the day of estrus, female produced significantly more net rotations than they did 24 h later, on the day of diestrus 1. It is suggested that sex and estrous cycle dependent differences in rotational behavior may be due to the direct or indirect modulation of mesostriatal dopamine activity by gonadal steroid hormone.

Amphetamine↗
PubMed1982

Sex differences and estrous cycle dependent variation in rotational behavior elicited by electrical stimulation of the mesostriatal dopamine system.

In this study electrical stimulation-induced rotational behavior was used as a behavioral index of mesostriatal dopamine (DA) activity to investigate gender and hormonal influences on the DA system. In female rats we found estrous cycle related variations in electrical stimulation-induced rotational behavior. A constant electrical stimulus produced significantly more turning on the day of estrus, than it did 24 h later, on diestrus 1. Gonadectomy attenuated contraversive rotational behavior in female, but not male rats. In contrast, ovariectomy had no effect on the ipsiversive rotational behavior produced by stimulation of the reticular formation. This evidence supports the idea that endogenous changes in gonadal hormone levels influence the functional activity of the mesostriatal DA system in a sexually dimorphic manner.

Animals↗
PubMed1981

Gonadectomy attenuates turning behavior produced by electrical stimulation of the nigrostriatal dopamine system in female but not male rats.

Rotational behavior induced by electrical stimulation of ascending dopamine neurons is used as a behavioral model to investigate gender and hormonal influences on extra-hypothalamic dopamine systems. Steroid hormones influence the metabolism of many dopaminergic drugs, and therefore this approach avoids the complications inherent in drug-induced behavior models of dopamine activity. We found that gonadectomy of female, but not male, rats severely attenuates electrical stimulation-induced rotational behavior. This suggests that some female gonadal steroid hormone(s) may modulate the activity of ascending dopamine neurons, while male gonadal hormones do not.

Analysis of Variance↗
PubMed1980

Monoamine replacement after reserpine: catecholaminergic agonists restore motor activity but phenylethylamine restores atropine-resistant neocortical low voltage fast activity.

A large dose of reserpine abolishes an atropine-resistant form of neocortical low voltage fast activity (LVFA) which normally accompanies certain patterns of motor activity in rats. An attempt was made to reverse this effect by replacement of specific monoamines or by injection of suitable agonists in rats pretreated with reserpine (10 mg/kg). The following compounds, alone or in various combinations, failed to restore atropine-resistant LVFA in reserpinized rats even though spontaneous motor activity was restored in many cases: L-DOPA (150-300 mg/kg) after pretreatment with an inhibitor of peripheral L-aromatic amino acid decarboxylase; 5-hydroxytryptophan (100-200 mg/kg); D-amphetamine (1-2 mg/kg); apomorphine (0.25-2.5 mg/kg); lysergic acid diethylamide (100-300 microgram/kg); and clonidine (0.5-1.0 mg/kg). In contrast beta-phenylethylamine was quite effective in restoring atropine-resistant LVFA and its effects were not diminished by pretreatment with alpha-methyl-p-tyrosine (400 mg/kg), chlorpromazine (15 mg/kg). It is suggested that a trace amine plays an essential role in the production of atropine-resistant LVFA independent of catecholamines.

5-Hydroxytryptophan↗
PubMed1980

Effects of hemicholinium-3 and choline on hippocampal electrical activity during immobility vs. movement.

Earlier studies have shown that the hippocampal rhythmical slow activity (RSA or theta) which may occur during behavioral immobility (IRSA) is abolished by systemically administered atropine (is atropine-sensitive), although the RSA which accompanies movements, such as walking, running or swimming (MRSA) is atropine-resistant. This study was designed to manipulate brain cholinergic activity in ways other than through the use of postsynaptic receptor antagonists, and to determine the effects of such manipulations on IRSA and MRSA. The IRSA elicited by electrical stimulation of the reticular formation in urethanized rats was severely attenuated by intraventricular injections of hemicholinium-3 (HC-3), a drug which depletes brain acetylcholine. A subsequent systemic injection of choline chloride restored IRSA elicited by electrical stimulation. In contrast, HC-3 had no deleterious effects on the MRSA recorded from freely moving rats. Therefore, atropine-sensitive IRSA is also HC-3 sensitive, and atropine-resistant MRSA is also HC-3 resistant. These results support the hypothesis that there are two pharmacologically distinct neurochemical systems which may produce hippocampal RSA. It is suggested that acetylcholine is necessary for the production of IRSA, but is not necessary for the production of MRSA.

Animals↗
PubMed1980

Hippocampal rhythmic slow activity (RSA; theta): a critical analysis of selected studies and discussion of possible species-differences.

The literature concerning the correlates of hippocampal RSA (theta) has seen a wealth of hypotheses generated from seemingly contradictory data. Two possible reasons for this are examined here. (1) An analysis of the maximum published RSA amplitudes in over 70 papers shows that there is enormous variation in how effective various research groups have been in tapping the hippocampal RSA generator zones. It is suggested that this variation is a major source of 'contradictory data'. The enormous variability is probably due to the fact that the laminar structure of the hippocampus, and the location of two seemingly independent 180 degrees out-of-phase RSA generators, results in very disparate signals being recorded by electrodes of different configurations. Electrodes which are not optimally placed result in records which may provide misinformation as to whether or not the hippocampus is in the RSA 'mode'. The results of studies with less than adequate records must therefore be viewed with great caution. (2) An explanation often evoked to account for much of the controversy is that of species differences. This idea is examined and it is suggested that there are probably not major species differences in that all of the species appropriately examined thus far have neural systems capable of producing both an atropine-sensitive and an atropine-resistant form of RSA. All species (with the exception of primates) also show relations of RSA to ongoing motor behavior. However, there are definitely species differences in the neural mechanisms underlying the production of atropine-sensitive, immobility-related RSA. Although all species appear to be capable of producing immobility-related RSA some do so only rarely (e.g. rats), while others do so frequently, particularly in response to sensory stimulation (e.g. rabbits, cats, guinea pigs). Therefore, the answer to the question as to whether there are species differences in the occurrence of RSA may be yes, or not, depending upon how specifically the question is posed.

Animals↗
PubMed1977

Are the dorsal noradrenergic bundle projections from the locus coeruleus important for neocortical or hippocampal activation?

Three different methods were used to examine the importance of the dorsal noradrenergic bundle projections from the locus coeruleus (LC) in activation of the neocortex and hippocampus in freely moving rats. (1) After cerebral norepinephrine (NE) was depleted by systemic neonatal injections of 6-hydroxydopamine (6-OHDA) both atropine-resistant and atropine-sensitive forms of hippocampal rhythmical slow activity (RSA; theta) and neocortical low voltage fast activity (LVFA) remained intact. Compared to controls the adult rats treated with 6-OHDA in infancy reared less in a 24 h time sample of behavior and ran less in running wheels. (2) Brain dopamine and NE were also depleted by systemic injections of alpha-methyl-p-tyrosine. Following this treatment rats were very inactive behaviorally. However, normal activation of the hippocampus and neocortex was still present. (3) In normal rats, electrical stimulation of the LC was relatively ineffective, compared to stimulation of nucleus reticularis pontis caudalis, in producing behavioral changes (especially locomotion) or either atropine-resistant or atropine-sensitive hippocampal RSA or neocortical LVFA. It is concluded that the locus coeruleus is not important for cerebral activation, and that mechanisms for cerebral activation are probably diffusely represented in the reticular core. The data also show that when attempting to assess the effect of experimental manipulations on brain activity it is essential to control for the possible effects of changes in behavior.

Animals↗