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O T Phillipson

Publications and source records attributed to O T Phillipson.

At least 37 records · Page 2Linked to original sources
PubMed1988

Afferent projections to the dorsal thalamus of the rat as shown by retrograde lectin transport. II. The midline nuclei.

Afferent projections to midline thalamic cell groups which innervate nucleus accumbens, were identified by the retrograde transport of unconjugated wheat germ agglutinin followed by the identification of labelled cell groups with immunocytochemistry. Large numbers of neurones were labelled in a variety of hypothalamic nuclei; principally in the medial preoptic area, anterior hypothalamic area, ventromedial, periventricular, arcuate and posterior hypothalamic nuclei, and in the supramammillary and lateral hypothalamic areas. Following rostral thalamic injections labelled cells were also found in the lateral septum, bed nucleus of the stria terminalis, and zona incerta. Prominent and localised label was found in the nucleus reticularis of thalamus at its most rostral medial tip. Cortical label was found in the ventral subiculum following rostral injections, and in the perirhinal cortex following mid-thalamic injections. In the brainstem label was found in central grey, laterodorsal tegmental nucleus, raphe, dorsal and ventral parabranchial nuclei and nucleus of the tractus solitarius. The results are discussed in the context of striatal function, particularly the nucleus accumbens, which is a component of the ventral striatum. Thus, the midline thalamic nuclei may provide an interface where a variety of inputs from many limbic regions and hypothalamic nuclei can influence nucleus accumbens function. Comparison of afferents to several thalamic nuclei directly related to striatal function and the prefrontal cortex show, that forebrain thalamic afferents from pallidal and hypothalamic sites, are organised with a clear topography. Some afferents suggest specific routes which may allow the reticular activating system to participate in the regulation of basal ganglia function.

Afferent Pathways↗
PubMed1988

The perception of visual ambiguous figures in schizophrenia and Parkinson's disease.

The frequency of reversal and dominance of aspect of three versions of an ambiguous Schröder staircase were studied in patients with a diagnosis of either schizophrenia or Parkinson's Disease (PD), and in a mixed group of psychiatric patients before and after prolonged neuroleptic therapy. It was found that schizophrenics perceived the staircases from above for significantly less time, and had a (nonsignificant) tendency to have more reversals than controls. PD patients saw the staircases from above for significantly more time, and also had (nonsignificantly) more reversals than controls. In the psychiatric patients, long term neuroleptic therapy had no significant effect on either reversal rate or dominance of aspect. When the contrast and the luminance of the stimulus were manipulated, normal subjects reported significantly less reversals and significantly increased dominance of the superior aspect when the contrast of the stimulus was reduced. Changing the luminance had no significant effect. The implications of these results for visual abnormalities in schizophrenia and Parkinson's Disease are discussed.

Adult↗
PubMed1987

Dopaminergic innervation of the primary visual cortex in the rat, and some correlations with human cortex.

Dopaminergic terminals have been identified in the primary visual cortex with three techniques; immunocytochemistry with an anti-dopamine antiserum, retrograde axonal transport techniques using unconjugated wheat germ agglutinin and HPLC determination of catecholamines and metabolites in microdissected sub-regions of occipital cortex in the rat. The results demonstrate a specific dopaminergic innervation, arising from the ventral tegmental area, which is found mainly in laminae VI and V, but with minor innervation also in lamina I. Dopaminergic innervation to adjacent cortical regions is also described. Neurochemical data from post-mortem human material suggests that a similar innervation exists in man. An analysis of the distribution of dopaminergic fibres in relation to the known connections and possible functions of the deep laminae of visual cortex suggests that dopaminergic axons may participate in the corticofugal control of visual afferent pathways.

Aged↗
PubMed1987

Regulation of dopamine function in the prefrontal cortex of the rat by the thalamic mediodorsal nucleus.

Dopamine (DA) utilisation has been assessed in the medial bank of the prefrontal cortex (FCx) and the agranular insular cortex (AgCx) of the rat in response to unilateral manipulations of the thalamic mediodorsal nucleus (MD). The ratios of 3,4-dihydroxyphenylacetic acid (DOPAC):DA and 4-hydroxy-3-methoxyphenylacetic acid (homovanillic acid, HVA):DA are used as indices of DA utilisation and were shown to increase in the ipsilateral FCx following electrical stimulation of lateral MD. A similar response was observed 1 hr after an infusion of the excitotoxin sodium ibotenate into lateral MD, although in this case the increase in DA utilisation in FCx was bilateral. Longer periods of recovery after ibotenate treatment (2 day and 1 week) produced DA utilisation ratios that had returned to near control values and by 1 week a significant decrease was detected in HVA:DA of the contralateral FCx. All treatments had little effect on DA utilisation in AgCx, although there was a tendency towards enhanced ratios after electrical stimulation and short-term ibotenate injection. These findings suggest that stimulation of MD neurones may tend to activate the DA system in their convergent terminal regions of cortex. It is argued that these influences result from interactions at the level of the DA terminal rather than at the cell bodies of mesocortical DA neurones.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1986

The agranular insular cortex: a site of unusually high dopamine utilisation.

Dopamine (DA) utilisation (expressed as homovanillic acid:DA) was compared in the medial prefrontal cortex (FCx), the agranular insular cortex (AgCx), the caudate-putamen (medial, CPM and lateral, CPL divisions) and the nucleus accumbens (NAc). DA utilisation in these regions decreased in the order AgCx greater than FCx greater than CPM, CPL, NAc, whilst the concentration of DA decreased in the reverse order. Thus, although fewer DA neurones appear to innervate AgCx compared with FCx, the rate of DA utilisation/release is much greater in AgCx. It is suggested that this apparently more marked activity in DA neurones innervating AgCx may reflect a relative lack of autoreceptor control.

Animals↗
PubMed1986

Modification of visual orientation illusions by drugs which influence dopamine and GABA neurones: differential effects on simultaneous and successive illusions.

The effects of haloperidol, nomifensine and lorazepam on the visual tilt illusion were studied in normal volunteers. Haloperidol and nomifensine produced no significant changes in the illusion, although in previous work they had been found to reduce and enhance, respectively, a closely related illusion, the tilt aftereffect. By contrast, lorazepam produced a dose-related increment in the size of the tilt illusion, but had no effect on the tilt aftereffect. The results are discussed in relation to proposed mechanisms which may underlie the two kinds of illusion. The differential effects of individual drugs on the two illusions may reflect their differing actions on two processes: lateral inhibition and adaptation in visual channels.

Adolescent↗
PubMed1986

Effects of haloperidol and nomifensine on the visual aftereffects of tilt and movement.

An antipsychotic and two antidepressant drugs were studied for their effects on the visual aftereffects of tilt and movement in normal volunteers. Compared with placebo, haloperidol reduced the aftereffects. The antidepressant nomifensine enhanced the tilt but not the movement aftereffect, while maprotiline (another antidepressant) had no significant effect on either aftereffect. Control experiments showed that these changes were unlikely to have resulted from drug induced alterations in scanning eye movements during adaptation. The results are discussed with reference to possible dopaminergic influences on the visual system, and to some of the symptoms of schizophrenia.

Adult↗
PubMed1986

Thalamic control of dopaminergic functions in the caudate-putamen of the rat--I. The influence of electrical stimulation of the parafascicular nucleus on dopamine utilization.

A neurochemical response of four dopamine-rich brain regions to unilateral electrical stimulation of the parafascicular thalamic nucleus was examined in the halothane-anaesthetized rat. Tissue concentrations of dopamine and its two major metabolites, 3,4-dihydroxyphenylacetic acid and 4-hydroxy-3-methoxyphenylacetic acid, were assayed by a high performance liquid chromatographic technique in samples of caudate-putamen complex, nucleus accumbens, prefrontal cortex and substantia nigra. The ratios of metabolite to parent amine concentrations were taken as indices of dopamine utilization. Halothane anaesthesia alone evoked significant bilateral increases of dopamine utilization in every brain region studied. Electrical stimulation of one parafascicular nucleus produced further bilateral elevations of dopamine utilization in the caudate-putamen complex without altering these parameters in the substantia nigra. In the prefrontal cortex, however, thalamic stimulation resulted in significant bilateral decreases of dopamine utilization. Electrical stimulation of cortical or other thalamic areas did not evoke this regional pattern of dopamine utilization. It is argued that these indices of dopamine utilization together serve as reliable indicators of synaptic dopamine release and it is concluded that the parafascicular thalamus is capable of facilitating dopaminergic neurotransmission in the caudate-putamen by a mechanism that is probably independent of changes in dopamine cell firing rate. An anatomical analysis suggests that a thalamo-cortical-striatal route is most likely to mediate this function.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1986

Thalamic control of dopaminergic functions in the caudate-putamen of the rat--II. Studies using ibotenic acid injection of the parafascicular-intralaminar nuclei.

We have investigated the role of the parafascicular-intralaminar thalamus in the regulation of dopaminergic function in the caudate-putamen by making unilateral injections of the excitotoxin, ibotenic acid, into the thalamus of the halothane-anaesthetized rat. Dopamine utilization was measured at 4 h, 18 h, and 7 days after operation in microdissected tissue from caudate-putamen, substantia nigra, and nucleus accumbens. High performance liquid chromatography with electrochemical detection was used to simultaneously determine dopamine, 3,4-dihydroxyphenylacetic acid and homovanillic acid. Dopamine utilization was recorded as a ratio of metabolite to its parent amine. At 4 h following injection large bilateral increases in dopamine utilization were recorded in both medial and lateral sectors of caudate-putamen. The percentage increases found for homovanillic acid-based ratios were larger than those found for 3,4-dihydroxyphenylacetic acid-based ratios. These results probably reflect increased dopamine release resulting from the acute effects of ibotenic acid. These changes were independent of dopamine utilization ratios recorded in the substantia nigra, which showed no change either ipsilateral or contralateral to the injection. In contrast to these findings, at 7 days following injection, dopamine utilization ratios were reduced both ipsilateral and contralateral to the injection, although only the ipsilateral reductions were significant. Again, no change was found for this survival time in the substantia nigra. At 18 h survival an intermediate pattern between the 4 h and 7 day result was found. In the nucleus accumbens, ibotenic acid injection produced similar results to those found in caudate-putamen, i.e. a bilateral increase in dopamine utilization at early time intervals and a unilateral ipsilateral decrease at long intervals following injection. These results show that dopamine release in the caudate-putamen is sensitive to experimentally induced changes in neural activity and lesions of its thalamic input. Since the effect of presumed stimulation is markedly greater than lesion, it would appear that, under the conditions employed in these experiments, the thalamus is relatively silent; a suggestion consistent with other evidence. Furthermore, since the changes found occurred in the absence of changes in utilization ratios in the substantia nigra, the mechanisms whereby thalamus regulates dopamine release may be exerted via a local circuit and/or a presynaptic mechanism in the region of dopamine terminals. The anatomical routes responsible for these effects are discussed.(ABSTRACT TRUNCATED AT 400 WORDS)

3,4-Dihydroxyphenylacetic Acid↗
PubMed1986

Thalamic control of dopaminergic functions in the caudate-putamen of the rat--III. The effects of lesions in the parafascicular-intralaminar nuclei on D2 dopamine receptors and high affinity dopamine uptake.

Dopamine receptor binding in the caudate-putamen was studied following bilateral lesions of the thalamostriatal pathway. Receptor binding was assayed using [3H]spiperone and defined with both (+)-butaclamol and S(-)-sulpiride. Radiofrequency lesions resulted in an increase in the Bmax of [3H]spiperone binding defined with both (+)-butaclamol and S(-)-sulpiride between 7 and 14 days following surgery. At longer survival times a fluctuating response was seen in which a decrease in receptor binding was observed at 28 days following lesion and a further rise again at 70 days. At no time point was significant change in Kd recorded. Further experiments were carried out to control for the possible effects of damage to fibres of passage and for inadvertent damage to habenula, as well as to define the receptor subtype involved. Ibotenic acid lesions resulted in similar effects to those reported with the radiofrequency method. Thus, 7 days following lesion, Bmax for (+)-butaclamol-defined [3H]spiperone binding increased by approximately 14-20% over that recorded in sham-lesioned animals. Using S(-)-sulpiride to define binding, Bmax was found to increase 13-17% in the same membrane preparations. Similar results were obtained in experiments at 14 days following ibotenic acid induced lesions. Again, no change in Kd was recorded. When radiofrequency lesions were made, which were largely restricted to habenula and associated fibres of passage, only small [(+)-butaclamol defined] or insignificant [S(-)-sulpiride defined] changes in Bmax were recorded. Combined radiofrequency lesions of habenula and ibotenic acid lesions of the thalamus resulted in a larger increase in Bmax for (+)-butaclamol defined binding than with S(-)-sulpiride defined binding. Our interpretation of these findings, in the light of the histology of the lesions, is that the predominant effect of removing thalamic input to the caudate-putamen is an increase in the number of D2 receptors, but without any change of affinity. A small component of the change in Bmax defined with (+)-butaclamol found with radiofrequency lesions may be due to a response at non-dopamine sites (possibly a 5-hydroxytryptamine receptor subtype) following damage to other caudate-putamen afferents which pass near the habenula or fasciculus retroflexus. Following unilateral ibotenic acid lesions of the thalamus, the number of high affinity uptake sites for dopamine was increased at long survival times.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

A semiautomated analysis method for catecholamines, indoleamines, and some prominent metabolites in microdissected regions of the nervous system: an isocratic HPLC technique employing coulometric detection and minimal sample preparation.

The application of a commercially available coulometric electrochemical detector to the automated HPLC analysis of some monoamines and their metabolites in microdissected areas of the rat nervous system is described. Apart from the stability and high sensitivity of the system, other appealing features of the technique are the facile sample preparation and long-term sample storage characteristics which show minimal analyte degradation. Basal values of some regional monoamine and metabolite concentration are listed together with a brief appendix that serves as a user's guide to the operation and maintenance of the detection system.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1985

The topographic order of inputs to nucleus accumbens in the rat.

Afferents to the nucleus accumbens have been studied with the retrograde transport of unconjugated wheatgerm agglutinin as detected by immunohistochemistry using the peroxidase-antiperoxidase method, in order to define precisely afferent topography from the cortex, thalamus, midbrain and amygdala. Cortical afferent topography was extremely precise. The largest number of cells was found following injections to the anterior accumbens. Anteromedial injections labelled a very large extent of the subiculum and part of the entorhinal cortex. Anterolateral injections produced less subicular and entorhinal label but also labelled the posterior perirhinal cortex. Posteromedial injections labelled only the ventral subiculum and a few cells in the adjacent medial entorhinal cortex. Posterolateral injections labelled few lateral entorhinal neurones but did label a long anteroposterior strip of perirhinal cortex. Prefrontal cortex label was found only after anterior accumbens injections. In the amygdala labelled neurones were found in cortical, central, lateral posterior, anteromedial and basolateral nuclei. Basolateral amygdala projected chiefly to the anteromedial accumbens and central nucleus to anterolateral accumbens. Only a weak amygdala label was found after posterior accumbens injections. In the ventral tegmental area, the midline interfascicular nucleus projected only to medial accumbens. The paranigral ventral tegmentum projected chiefly to the medial accumbens and the parabrachial area chiefly to the lateral accumbens. In the thalamus, heaviest label was found after anterior accumbens injections. Most cells were found in the paraventricular, reuniens and rhomboid nuclei and at posterior thalamic levels lying medial to the fasciculus retroflexus. There was only restricted topography found from thalamic sites. Retrograde label was also found in the ventral pallidum and lateral hypothalamus. Single small injection sites within accumbens received input from the whole anteroposterior extent of the thalamus and ventral tegmentum. The medial accumbens was found to have a close relationship to habenula, globus pallidus and interfascicular nucleus. It appeared that the heaviest volume of inputs projected to anteromedial accumbens, where output from hippocampus (CAI), subiculum, entorhinal and prefrontal cortices converged with output from amygdala, midline thalamus and ventral tegmentum.

Amygdala↗
PubMed1985

Perceptual changes in schizophrenia: a questionnaire survey.

Questionnaires were completed by 73 volunteers with a history of probable schizophrenia, and by 67 patients admitted to the accident wards of a general hospital. A high incidence of sensory distortions was recorded in the schizophrenic group compared with the controls, distortions of brightness contrast being the most common. Many schizophrenic patients reported that such distortions were reduced or removed early in treatment. Patients who reported visual distortions also tended to report visual hallucinations. The results are discussed with reference to the hypothesis that perceptual malfunction may underlie some other schizophrenic disorders such as delusions or catatonia.

Adult↗
PubMed1984

Evidence that thalamic efferent neurones are non-cholinergic: a study in the rat with special reference to the thalamostriatal pathway.

Controversy surrounds the question as to whether some fibres of the thalamostriatal projection, are cholinergic. The present experiments show that lesions of the parafascicular-intralaminar thalamus produced no reductions in choline acetyltransferase (ChAT) activities in any area of microdissected rat caudate-putamen complex or dorsolateral frontal cortex. We conclude that thalamostriatal projections are entirely non-cholinergic. Furthermore, lesions of the mediodorsal or periventricular thalamus resulted in no change in ChAT activities in their terminal projection areas (medio-/orbitofrontal cortices and nucleus accumbens, respectively). The probability that all thalamic outputs are non-cholinergic is discussed.

Animals↗
PubMed1983

Anterograde and retrograde labelling of CNS pathways with unconjugated lectins using the unlabelled antibody enzyme method.

A method for demonstrating the anterograde and retrograde transport of unconjugated lectins in the CNS is given using the labelled antibody enzyme technique. Successful labelling of a variety of pathways is demonstrated using wheat germ agglutinin (WGA) and concanavalin A (Con A). Exceptionally large numbers of neurones labelled by retrograde transport were detected in each area. Using this method afferents to the mediodorsal thalamus are reported from prefrontal, cingulate and perirhinal cortex, substantia innominata, magnocellular and lateral preoptic area, ventral pallidum and diagonal band of Broca. In addition it is shown that large numbers of neurones of the periventricular hypothalamus and periaqueductal central grey of the mesencephalon techniques and further applications of the method are outlined.

Animals↗
PubMed1983

Effects of chlorpromazine and promazine on the visual aftereffects of tilt and movement.

The effects of chlorpromazine (CPZ) and promazine on the visual aftereffects of tilt and motion were measured. CPZ markedly reduced the strength of both aftereffects, while promazine produced a smaller and not always significant reduction. Control experiments suggested that the effects were produced in the central visual system rather than by several possible peripheral artefacts or by drowsiness. The effects are discussed with reference to the pharmacological activity of the drugs and their influence on the strength of inhibition in the visual cortex, both in normal subjects and in schizophrenic illness.

Adaptation, Ocular↗