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A Drumheller

Publications and source records attributed to A Drumheller.

18 recordsLinked to original sources
PubMed2001

The availability heuristic with famous names: a replication.

In two experiments, 195 Canadian undergraduates initially judged a list of 25 names (12 famous men and 13 nonfamous women or 12 famous women and 13 nonfamous men) for familiarity. Contrary to previous research, subsequent estimates of the perceived number of men's and women's names were not higher when the names were famous than nonfamous. When the estimated differences were compared to the true difference (-1), famous names were judged more numerous than nonfamous names, but the size of the effect (d = 0.34) was smaller than in previous research. Reasons for these findings are discussed.

Famous Persons↗
PubMed1999

CCK4-induced panic in healthy subjects II: neurochemical correlates.

Cholecystokinin tetrapeptide (CCK4) induces symptoms similar to those of panic attack. The present study investigated the effects of CCK4 administration on catecholaminergic system. In this double blind, randomised, crossover experiment, 16 healthy subjects received injections of either 25 microg of CCK4 or placebo on two separate occasions. Platelet and plasma catecholamine concentrations were assessed before the administration and compared to post-injection values. The results clearly show that both plasma and platelet concentrations of catecholamines are significantly affected by CCK4. Plasma norepinephrine (NE) and epinephrine (EPI) raised significantly above baseline in the immediate post-CCK4 period, while in plasma dopamine (DA), the significant increases were delayed. In the platelets, significant post-CCK4 increases of NE and EPI concentrations were observed with a delay of several minutes. In summary, we have demonstrated that, in healthy subjects, CCK4 increases peripheral concentrations of catecholamines in both plasma and platelets, with the most consistent changes occurring in platelet NE and plasma EPI concentrations.

Adult↗
PubMed1995

Differential effects of low versus high doses of apomorphine on retinal dopamine metabolism in light- and dark-adapted rabbits.

Previous electrophysiologic results from this laboratory indicate that apomorphine exerts a differential dose-related effect on rabbit electroretinograms, with low doses increasing the b-wave and higher doses decreasing this parameter. Results were interpreted as reflecting apomorphine's agonistic properties at two different receptors: 1.0 mg/kg acting at the postsynaptic site, and the lower dose, 0.01 mg/kg, preferentially stimulating inhibitory autoreceptors. The purpose of this experiment was to investigate further this hypothesis by determining retinal levels of dopamine, dihydroxyphenylacetic acid, and homovanillic acid in retinas of light- or dark-adapted rabbits treated with saline, 1.0, 0.1, or 0.01 mg/kg apomorphine intravenously. Results indicate that in dark-adapted rabbits only the highest dose tested, 1.0 mg/kg, decreased dopamine concentrations. In animals exposed to light, the lowest dose tested, 0.01 mg/kg, significantly reduced dopamine and metabolite levels, whereas the highest dose unexpectedly increased retinal dopamine turnover. Results are discussed in terms of receptor sites and the influence of lighting conditions.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

Selective effects of retinal dopamine depletion on partial ischemia-induced electroretinographic hyperresponses in rabbits.

The interaction of retinal dopamine depletion and partial ischemia on the a- and b-wave amplitudes and implicit times of the electroretinogram was examined in adult pigmented rabbits. Seven days after 6-hydroxydopamine treatment, which resulted in a depletion of the amine, partial retinal ischemia was induced by raising the intraocular pressure. As expected, moderate elevation of intraocular pressure produced increases in both a- and b-wave amplitudes. Amplitude hyperresponses were significantly reduced in dopamine-depleted retinas. These reductions were more prominent with relatively lower intensities. However, response delays were not shortened but lengthened by 6-hydroxydopamine pretreatment. Together, these results point to a selective role of dopamine in partial retinal ischemia induced by moderate elevation of intraocular pressure in rabbits.

Animals↗
PubMed1994

Neurochemical effects of neuropeptide Y (NPY) and NPY2-36.

Our previous in vivo structure-activity studies suggested that the putative receptors mediating the effects of NPY and NPY2-36 on food intake and body temperature following ICV administration are pharmacologically different. In the present study, we examined and compared dose related effects of NPY and NPY2-36 on levels of norepinephrine (NE), dopamine (DA) and its main metabolites, dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA), as well as serotonin (5-HT) and its metabolite, 5-hydroxyindolacetic acid (5-HIAA), in several brain regions of the rat, including: frontal cortex, hypothalamus, amygdala, septum, nucleus accumbens, corpus striatum, globus pallidus, substantia nigra and hippocampus. NPY and NPY2-36 (10 or 20 micrograms) were administered intraventricularly and the regional levels of the amines and metabolites were assessed 30 min following administration. Results indicate that both doses of NPY decreased NE levels within the hypothalamus. Furthermore, DOPAC concentrations were increased in this region while DA and HVA remained unchanged. The most pronounced neurochemical effects of NPY were found in the hippocampus, where the peptide produced dose related increases in DA, DOPAC and HVA. On the other hand, NPY2-36 significantly increased NE, DA and its metabolite DOPAC in both the amygdala and septum. The metabolism of DA was most obviously affected in the hippocampus and frontal cortex where levels of DA and DOPAC were significantly increased. 5-HT was affected in both the hypothalamus and globus pallidus where DA and its metabolite HVA were also increased.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

Multidimensional locus of control and attitudes toward mental illness.

University students (55 women and 37 men) participated in a study of the relationship between multidimensional locus of control and attitudes toward mental illness as measured by the five factors of the Opinions About Mental Illness scale. Semipartial correlations suggested that scores on multidimensional locus of control were related to scores on three of the five factors but that the pattern of relationships is subject to gender differences.

Adolescent↗
PubMed1994

Effects of dextromethorphan on ischemia induced electroretinogram changes in rabbit.

The present study was undertaken to determine whether dextromethorphan (DM), a potent N-methyl-D-aspartate antagonist, could attenuate the effects of ischemia on rabbit ERG. Retinal ischemia was induced by increasing intraocular pressure to 120 mm Hg for 30, 60, or 90 min. DM was intravenously administered before ischemia and maintained throughout the entire experimental period. ERGs were recorded prior to, during, and after ischemia. The results indicate that the b-wave hyperresponses and the delays in implicit times induced by 30 min. ischemia were suppressed by the administration of DM. Similar findings were obtained when ischemia lasted for 60 min, except that DM did not improve delayed implicit times, suggesting that cellular injury is still present. ERG changes resulting from 90 min ischemia were not reversed by DM treatment. Effects of DM treatment on a-wave were less prominent. Together, our results further support that DM can to some extent alleviate ischemic injury in the rabbit retina.

Animals↗
PubMed1993

Dextromethorphan attenuates the effects of ischemia on rabbit electroretinographic oscillatory potentials.

Dextromethorphan has been shown to protect against ischemic tissue damage. We investigated the effects of dextromethorphan on electroretinographic oscillatory potentials in retinal ischemia. Retinal ischemia was induced in rabbits by increasing intraocular pressure to 120 mm Hg for 30, 60 or 90 minutes. Dextromethorphan was intravenously administered before ischemia and maintained throughout the whole period of experiments. Oscillatory potentials were recorded before and during ischemia as well as 4 hours of recirculation after ischemia. As expected, all oscillatory potentials were decreased after 60 and 90 minutes of ischemia. However, after 30 minutes of ischemia followed by 4 hours of recirculation, amplitudes of P2 were elevated whereas those of P3 and P4 were decreased with normal P1 amplitudes. Dextromethorphan administration diminished the effects of 30 minutes of ischemia on oscillatory potentials and partially attenuated the effects of 60 minutes of ischemia, whereas the effects of 90 minutes of ischemia could not be reversed by dextromethorphan treatment. These results indicate that electroretinographic oscillatory potentials could be useful indicators to evaluate retinal function in the ischemic condition and that dextromethorphan can attenuate the effects of relatively short periods of ischemia on rabbit electroretinographic oscillatory potentials.

Acute Disease↗
PubMed1993

Effects of calcitonin gene-related peptide on the rabbit electroretinogram.

In order to better understand the role of Calcitonin gene-related peptide (CGRP) in mammalian retina, the dose related effects of human CGRP (hCGRP) on rabbit electroretinogram (ERG) were examined in the present study. CGRP was administered intraocularly in doses of 0.1, 1.0 and 10.0 micrograms. ERG A- and B-wave as well as oscillatory potentials (P1, P2, P3 and P4) were recorded. The highest dose of CGRP (10.0 micrograms) significantly increased the amplitudes of the A-wave and OP components (P1, P2, P3 and P4) produced by relatively high stimulus intensity. The same dose of the peptide also enhanced B-wave amplitude at all intensities studied. The effects of the intermediate dose of CGRP (1.0 microgram) on the B-wave amplitudes were dependent on stimulus intensities. B-wave amplitudes at high stimulus intensities were not affected by 1.0 microgram of CGRP but were significantly increased with relatively lower stimulus intensities. The amplitudes of P3, one of OP components, were significantly increased. However, amplitudes of A-wave and other OP components (P1, P2 and P4) were not affected by 1.0 microgram CGRP. The lowest dose of the peptide (0.1 microgram) did not affect any amplitudes of ERG components. Implicit times of A-wave, B-wave and OP components were not significantly affected by the different doses of CGRP. Taken together, these results indicate that CGRP may play a functional role in modulating retinal responses to photic stimulation.

Animals↗
PubMed1993

Atypical neuroleptic-like behavioral effects of neurotensin.

To better characterize the neuroleptic-like properties of neurotensin, the dose-related effects of the peptide on the following behavioral phenomena were examined: a) the yawning-penile erection syndrome induced by small doses of the dopamine agonists apomorphine and N-propylnorapomorphine (NPA); b) yawning produced by the anticholinesterase physostigmine, and c) stereotyped climbing and sniffing produced by a larger dose of apomorphine. Several doses of the peptide were injected intraventricularly 30 min prior to drug administration. Results indicate that neurotensin markedly decreased yawning and penile erections produced by both apomorphine and NPA. These effects were seen with relatively small doses (0.9-3.75 micrograms). Neurotensin also potently decreased physostigmine-induced yawning with the initial inhibitory effect seen with 50 ng of the peptide. Apomorphine-induced climbing was significantly attenuated with 30.0 and 60.0 micrograms neurotensin, whereas stereotyped sniffing was unaffected, even by doses as large as 120.0 micrograms. These findings suggest that neurotensin might antagonize dopamine autoreceptors and indicate that the peptide possess central anticholinergic activity. Furthermore, these results lend support to the hypothesis that neurotensin's profile of central actions resemble that of atypical neuroleptics.

Animals↗
PubMed1993

Effects of experimentally induced ischemia on dopamine metabolism in rabbit retina.

PURPOSE: To determine the role of dopamine in experimentally induced retinal ischemia. Experiment 1 was designed to study the effects of ischemic levels on dopamine (DA) metabolism. Experiment 2 evaluated the effects of ischemic duration on DA metabolism. The effects of recirculation time after ischemia on DA metabolism were investigated in experiment 3. METHODS: Ischemia was produced by raising intraocular pressure (IOP) in rabbits. Three levels of ischemia were used--level A, level B, and level C--representing 50%, 75%, and 100%, respectively, of the IOP necessary to produce total ischemia. Retinal levels of DA and its main metabolites, homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC), were measured by high-performance liquid chromatography with electrochemical detection. RESULTS: Experiment 1 showed that at ischemic level B, DA contents were significantly reduced, but neither DOPAC nor HVA concentrations were altered. The reductions of retinal DA, DOPAC, and HVA concentrations were seen at level C without altering the ratio index. Level A ischemia did not alter DA metabolism. In experiment 2, significant reductions in DA, DOPAC, and HVA concentrations were found at both 30 and 60 minutes in the ischemic group, whereas the ratio DOPAC/DA and (HVA + DOPAC)/DA were significantly decreased only in the 60-minute ischemic group. Five-minute total ischemia did not alter DA metabolism. In experiment 3, concentrations of DA were still significantly decreased at 30 minutes of recirculation after ischemia, but DOPAC and HVA levels were back to normal. However, the ratios of DOPAC/DA, HVA/DA, and (HVA + DOPAC)/DA were significantly elevated. After 90 and 240 minutes of recirculation, retinal DA contents had returned to normal values, but DOPAC and HVA concentrations as well as all ratio indices of DA metabolism were still enhanced. CONCLUSION: Dopamine metabolism is altered during and after retinal ischemia. Dopamine may play a contributing role in ischemia.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1991

Antiparkinson-like effects of neurotensin in 6-hydroxydopamine lesioned rats.

The aim of the present study was to examine the effects of neurotensin in an animal model of Parkinson's disease (PD). Bilateral administration of 6-OHDA in the medial forebrain bundle at the level of the posterolateral hypothalamus of rats resulted in the appearance of the 3 principal neurological signs of PD: hypokinesia, rigidity and tremor. These symptoms were accompanied by severe losses of dopamine and its main metabolites in terminal regions of well-known dopamine pathways. Norepinephrine concentrations were also decreased in several regions but to a lesser extent than dopamine. Intracerebroventricular administration of neurotensin, in doses ranging from 7.5 to 120.0 micrograms, resulted in dose related attenuations of both muscular rigidity and tremors of animals. However, hypokinesia, defined as decreased motor activity was not significantly affected by the peptide. Administration of 120.0 micrograms of [Ala]NT, an inactive analogue of neurotensin, failed to alter any of the 3 neurological signs. Together, these results reveal selective antiparkinson-like effects of neurotensin in an animal model. The theoretical significance of these findings is discussed.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1991

Neurotensin selectively antagonizes apomorphine-induced stereotyped climbing.

In order to better characterize the neuroleptic properties of neurotensin, the dose-related effects of the peptide on stereotyped climbing, sniffing and licking induced by 0.6 mg/kg apomorphine were examined. The following doses of the peptide were injected intraventricularly 30 min prior to apomorphine administration: 0.9, 3.75, 30.0 and 60 micrograms. Results indicate that, whereas oro-facial stereotypies remained unaffected by the peptide, stereotyped climbing was significantly decreased with the two largest doses of neurotensin. These findings indicate that the profile of neurotensin's neurobehavioral effects is more akin to that of atypical than typical neuroleptics.

Animals↗
PubMed1991

Hypokinesia, rigidity, and tremor induced by hypothalamic 6-OHDA lesions in the rat.

Bilateral administration of 6-hydroxydopamine in the medial fore-brain bundle at the level of the posterolateral hypothalamus in rats resulted in hypokinesia, muscular rigidity and tremor as determined by various behavioral assessment procedures. These neurological signs were accompanied by marked decreases in the concentrations of dopamine and its main metabolites dihydroxyphenylacetic acid and homovanillic acid in both striatum and nucleus accumbens. Administration of apomorphine (1 mg/kg) or L-Dopa (60 mg/kg) reversed or totally abolished the hypokinesia, rigidity and tremor in lesioned animals. Together, the present findings demonstrate that bilateral intrahypothalamic administration of 6-OHDA results in the appearance of the three cardinal symptoms of Parkinson's disease in rats. This model should prove to be valuable for both the study of the neuropathological processes underlying the neurological signs of this disease and the screening of potential antiparkinson agents.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1987

Effects of retinal dopamine depletion on the rabbit electroretinogram.

This study evaluated the effects of intravitreal injections of 300 micrograms of 6-hydroxydopamine (6-OHDA) on electroretinogram (ERG) amplitudes and implicit response times of adult pigmented rabbits. One eye was injected intravitreally with 300 micrograms 6-OHDA and 600 micrograms ascorbic acid in a 0.3 ml 0.9% NaCl solution; the fellow eye received a similar solution containing only 600 micrograms ascorbic acid. Following this treatment ERG recordings were performed at 1, 4, and 7 days. After the last recordings, animals were sacrificed and retinas were isolated for biochemical analyses. Significant and progressive reductions in retinal concentrations of dopamine (DA) and its main metabolites homovanillic acid (HVA), and dihydroxyphenylacetic acid (DOPAC) were found in treated retinas. Concentrations of norepinephrine (NE), serotonin (5HT), and 5 hydroxyindoleacetic acid (5-HIAA) were not affected, thus demonstrating the specific neurotoxic action of 6-OHDA on retinal dopaminergic neurons. Concurrently, significant increases in ERG a- and b-wave amplitudes as well as in implicit response times were observed. These electrophysiological changes were progressive reaching a maximum 7 days after intravitreal injections. Changes in b-wave amplitudes and response times were more pronounced at low intensities of stimulation. These results clearly show that, in rabbits, selective decreases in retinal DA concentrations result in pronounced ERG changes, which offer additional evidence supporting a role for this transmitter in lateral inhibition in the retina.

Animals↗
PubMed1983

Rapid assay of human plasma carboxypeptidase N by high-performance liquid chromatographic separation of hippuryl-lysine and its product.

A rapid and sensitive method for measuring carboxypeptidase N (CPN) activity in human plasma is described. The procedure is based on the hydrolysis of a high-specificity/low-affinity substrate, hippuryl-L-lysine, to its products hippuric acid and lysine. The substrate and product are separated quantitatively by high-performance liquid chromatography in less than 10 min following a minimal sample preparation time. The advantages of this method over previous ones are discussed and data are presented demonstrating the reliability of this method for the routine clinical determination of CPN activity.

Carboxypeptidases↗
PubMedDate not supplied

[Changes in the B wave of cones and rods in diabetes mellitus induced by streptozotocin in rats].

The purpose of the present study was to evaluate the electroretinophysiological effects of streptozotocin-induced diabetes in the rat. More specifically, both B wave amplitudes and implicit times generated with various intensities of light stimulation were examined in diabetic animals adapted to either scotopic or photopic conditions. Results indicate that B wave amplitudes, but not implicit times, were differentially affected by these two conditions of light adaptation: amplitudes were significantly enhanced but markedly decreased under photopic and scotopic conditions respectively. The possible functional relationships between these specific ERG changes and our previous observations of selective alterations in retinal dopaminergic systems in this animal model of diabetes are discussed.

Animals↗