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T E Robinson

Publications and source records attributed to T E Robinson.

117 records · Page 7Linked to original sources
PubMed1977

Hippocampal electrical activity during waking behaviour and sleep: analyses using centrally acting drugs.

Rhythmical slow activity (RSA) occurs in the hippocampus under many conditions including waking behaviour, active sleep and surgical anaesthesia. Under all these conditions RSA, apparently, is produced by the coupled operation of CA1 and dentate gyrus generators. Two ascending brainstem systems appear capable of initiating activity in these coupled generators. One system, ascending via the diagonal band and medial septal nucleus, may contain cholinergic synapses since it is blocked by atropine and stimulated by eserine. The RSA produced by this system usually has a frequency of 4--7 Hz and can occur during total immobility during the waking state, active sleep or anaesthesia. A second ascending system produces RSA of higher frequency (usually 7--12 Hz) and is active during waking if, and only if, movements such as walking occur. During active sleep this system is active only during phasic muscular twitches. Anaesthetics (ether, urethane) and morphine abolish activity in this second system but it is resistant to atropinic and nicotinic drugs. Amphetamine stimulates, and major tranquillizers depress the atropine-resistant system but these drugs do not abolish its normal relation to behaviour. Neocortical activity appears to be controlled by two ascending systems which parallel closely those ascending to the hippocampus.

Anesthesia, General↗
PubMed1976

Life cycle studies with Eimeria magna Pérard, 1925.

Excystation of Eimeria magna required exposure to CO2 at body temperature followed by trypsin and bile. Incubation in the presence of CO2 produced marked effects on the inner layer of the oocyst wall. The evidence suggests that CO2 stimulates enzymic activity from within the oocyst rather than exerting a physico-chemical effect on the oocyst wall from the outside. Released sporozoites measured 19.65 X 3.33 mum. In the rabbit, E. magna undergoes at least 5 cycles of asexual schizogony before gametogony takes place. First-generation schizonts were observed at 30 hr, measured 15 X 11 mum and contained 4, 6, 8 or occasionally 12 merozoites; the merozoites were characterised by two very large and prominent refractile granules. As the infection progressed, schizont size and merozoite numbers became more variable; some schizonts contained 2-8 fat merozoites, many probably multinuclear, while other schizonts contained 12-100 thinner merozoites. First generation schizogony took place in the glands; all subsequent stages developed in the upper parts of the villi of the small intestine. Sexual forms have been seen as early as 96 hr, but maximum sexual activity was noted at 120-192 hr. Oocysts measured 35.87 X 24.05 mum. The first oocysts were passed 6-7 days after inoculation, with peak production at 8-9 days. Sporulation was optimal at 30 degrees C; higher temperatures inhibited sporulation, and were in time lethal, while sporulation would take place normally after suppression by cold for at least 11 months. Single oocyst inoculations indicated a maximum reproductive potential of 26.15 million. Pathogenic effects were mostly mild, amounting to growth depression over days 4-7 and softening of the faeces; occasionally diarrhoea and/or death occurred.

Animals↗
PubMed1976

Intraventricular anti-cholinergics do not block cholinergic hippocampal RSA or neocortical desynchronization in the rabbit or rat.

Electroencephalographic (EEG) electrodes and ventricular cannulae were implanted in 8 rabbits and 12 rats. Two anti-cholinergic agents, atropine sulfate and scopolamine hydrobromide, were given systemically (1-50 mg/kg) and intraventricularly (5-800 mug). Systemic but not intraventricular injections blocked sensory stimulation-induced or eserine-induced neocortical desynchronization and hippocampal RSA in rats and rabbits which were immobile and either undrugged or ethanol intoxicated. Systemic injections also blocked hippocampal RSA but not neocortical desynchronization in rats given sensory stimulation under urethane anaesthesia, while intraventricular injections only reduced RSA amplitude. Neither systemic nor intraventricular injections blocked neocortical desynchronization or hippocampal RSA recorded from animals when they walked in a motor driven wheel. These experiments support the hypothesis that there are two types of neocortical desynchronization and hippocampal RSA, one cholinergic and one non-cholinergic. They also suggest that atropine and scopolamine pass more readily to the neural system responsible for cholinergic EEG activity from the capillary bed than from the ventricular fluid.

Animals↗
PubMed1976

Methods in coccidiosis research: separation of oocysts from faeces.

Factors which may be important in the large-scale extraction of coccidial oocysts from faeces ha.ve been investigated with Eimeria tenella. Age of bird, inoculum, feeding status at the time of inoculation, period of collection, feeding status during collection, collection medium, homogenization and sieving, flotation, washing, sporulation and further purification have all been considered. The aim has been to establish a method to produce the maximum number of oocysts of a required degree of purity and viability, with the expenditure of the minimum amount of physical effort, time, animals and chemicals. In our method, groups of chickens 3-4 weeks of age are inoculated with 5000 oocysts of E. tenella and food is supplied ad lib. Over the period 5-8 days after inoculation, faeces are collected in trays containing 2% (w/v) potassium dichromate solution, while food intake is restricted. The faecal material is homogenized, passed once through 40 and 100 mesh sieves, centrifuged and the oocysts recovered from the sediment by 3 flotations in saturated salt solution. Following washing, oocysts are sporulated by forced aeration at 30 degrees C and may be further purified by hypochlorite treatment, or passage in 5% Tween 80 solution through a glass bead column followed by sucrose density gradient centrifugation. Routine passages along these lines over a 5 year period have given a recovery of 46% of the oocysts excreted by over 7000 birds.

Animals↗
PubMedDate not supplied

The neural basis of drug craving: an incentive-sensitization theory of addiction.

This paper presents a biopsychological theory of drug addiction, the 'Incentive-Sensitization Theory'. The theory addresses three fundamental questions. The first is: why do addicts crave drugs? That is, what is the psychological and neurobiological basis of drug craving? The second is: why does drug craving persist even after long periods of abstinence? The third is whether 'wanting' drugs (drug craving) is attributable to 'liking' drugs (to the subjective pleasurable effects of drugs)? The theory posits the following. (1) Addictive drugs share the ability to enhance mesotelencephalic dopamine neurotransmission. (2) One psychological function of this neural system is to attribute 'incentive salience' to the perception and mental representation of events associated with activation of the system. Incentive salience is a psychological process that transforms the perception of stimuli, imbuing them with salience, making them attractive, 'wanted', incentive stimuli. (3) In some individuals the repeated use of addictive drugs produces incremental neuroadaptations in this neural system, rendering it increasingly and perhaps permanently, hypersensitive ('sensitized') to drugs and drug-associated stimuli. The sensitization of dopamine systems is gated by associative learning, which causes excessive incentive salience to be attributed to the act of drug taking and to stimuli associated with drug taking. It is specifically the sensitization of incentive salience, therefore, that transforms ordinary 'wanting' into excessive drug craving. (4) It is further proposed that sensitization of the neural systems responsible for incentive salience ('for wanting') can occur independently of changes in neural systems that mediate the subjective pleasurable effects of drugs (drug 'liking') and of neural systems that mediate withdrawal. Thus, sensitization of incentive salience can produce addictive behavior (compulsive drug seeking and drug taking) even if the expectation of drug pleasure or the aversive properties of withdrawal are diminished and even in the face of strong disincentives, including the loss of reputation, job, home and family. We review evidence for this view of addiction and discuss its implications for understanding the psychology and neurobiology of addiction.

Adaptation, Physiological↗
PubMedDate not supplied

Sex differences in amphetamine-elicited rotational behavior and the lateralization of striatal dopamine in rats.

Sex differences are described in both a lateralized behavior (amphetamine-elicited rotation) and in the lateralization of striatal dopamine (DA) content. Amphetamine (AMPH) elicited significantly more partial turns, total rotations and lateralized (net) rotations in female, than in male rats. The two sexes also differed in their pattern of net rotations over time. In females, but not males, the striatum containing higher DA levels after amphetamine was consistently found to be contralateral to the dominant direction of rotation observed in the first 5 min interval after AMPH. No relationship was found between rotational behavior and medial frontal cortex DA or norepinephrine. The results are discussed in reference to cerebral lateralization in humans, and to possible sex differences in the modulatory effects of gonadal steroid hormones on striatal function.

Animals↗