Biomedical subjects

H Tanila

Publications and source records attributed to H Tanila.

44 records · Page 3Linked to original sources

PubMed1991

Effects of atipamezole, a novel alpha 2-adrenoceptor antagonist, in open-field, plus-maze, two compartment exploratory, and forced swimming tests in the rat.

The behavioral effects of atipamezole (0.5-4.5 mg/kg), a new and highly selective alpha 2-adrenoceptor antagonist, were studied in four behavioral models: open-field, elevated plus-maze, two compartment exploratory test and forced swimming test. Atipamezole (1.5 and 4.5 mg/kg) produced a dose-dependent suppression of locomotor activity in the open field test. In the two compartment exploratory test, the same doses of atipamezole decreased locomotor activity in a 5 min test but not in a 10 min test. The numbers of transitions between the compartments were not significantly affected by atipamezole. Doses of 0.5-4.5 mg/kg did not significantly change the time spent in the open arms or the total number of arm entries in the plus-maze, and doses of 1.5 and 4.5 mg/kg decreased defecation marginally. Vocalization during the forced swimming test was increased by atipamezole (1.5 mg/kg) but the duration of immobility was not increased over the dose range (0.5-1.5 mg/kg) of atipamezole used. Our results suggest that, in the rat, atipamezole decreases motor activity in the early phase of the exploration of new surroundings. In the doses used, atipamezole may suppress defecation and increase vocalization in rats.

Adrenergic alpha-Antagonists↗

PubMed1991

Effect of systemic medetomidine, an alpha 2 adrenoceptor agonist, on experimental pain in humans.

The effect of systemic (intravenous) medetomidine, an alpha-2 adrenoceptor agonist, on pain thresholds was studied in healthy human subjects (n = 6). Medetomidine produced a dose-dependent (cumulative doses: 25 and 50 micrograms) sedative effect evaluated by visual analog scale. Also, a dose-dependent decrease of blood pressure but not of heart rate was seen after administration of medetomidine. Pain threshold to electric stimulation of the tooth pulp and cutaneous heat pain threshold were uninfluenced by medetomidine. An index of cutaneous thermal sensitivity to innocuous stimuli, the width of the thermoneutral zone, also was uninfluenced by medetomidine. Medetomidine produced a significant attenuation of the affective-motivational component (unpleasantness) of tourniquet-induced ischemic pain, whereas the sensory-discriminative component (pain magnitude estimate) of the ischemic pain was not attenuated. The results suggest that systemic medetomidine alone at subanesthetic but sedative and hypotensive doses does not significantly influence the intensity and thresholds of experimental pain, whereas the affective-motivational component of pain can be attenuated.

Adrenergic alpha-Agonists↗

PubMed1990

Vertical and horizontal coding of space in the monkey dorsolateral prefrontal cortex.

Single cell activity in the dorsolateral prefrontal cortex was recorded in a monkey performing a delayed alternation (DA) task in 3 directions, to the left, to the right, and upwards. Among the 127 units studied in all three directions, 18 neurons were spatially selective in one direction (to the left, to the right or upwards), 37 neurons in two directions and 8 neurons in each 3 directions during the performance of the DA task. Of the 9 neurons that were spatially selective upwards, 8 had a specific pattern of activity during the delay period and one during the response period. When several spatial directions are studied in a DA task, as in this work, it becomes evident that the prefrontal cortex contains a large number of spatially selective neurons. The results of this study suggest that there is a spatial memory map in the prefrontal cortex which is needed not only when a DA task is performed to the left and to the right but also in the upward direction.

Animals↗

PubMed1989

Comparison of tactile discrimination ability of visually deprived and normal monkeys.

The tactile discrimination ability of visually deprived and normal monkeys was tested to study whether loss of vision would improve the utilization of the tactual sense. Three normally sighted monkeys and three monkeys that had been deprived of vision during the first year of their life were trained in two tactile discrimination tasks by using a reward system in which the animals received a raisin or half a peanut under a correctly chosen wooden block. Discrimination was based on the gradual roughness or size of various blocks. When the monkeys had learned the tasks to the criterion, discrimination thresholds were determined. All monkeys improved their performance in both tasks with time, but no statistically significant differences between the performance of the two groups of monkeys were obtained. These results suggest that although the representation of the tactual sense in the cortical association areas has been shown to increase as a result of visual deprivation during the early sensitive period of life, increased representation does not improve the tactual discrimination ability of simple tactual stimuli.

Animals↗

PubMed1987

Late effects of early binocular visual deprivation on the function of Brodmann's area 7 of monkeys (Macaca arctoides).

It has been shown earlier that binocular visual deprivation during the early sensitive period of life reduces the representation of visual functions in the posterior parietal association cortex of monkeys, in Brodmann's area 7 (Exp. Brain Res., 42 (1981) 1-8). Moreover, the representation of somatic functions increases suggesting that competitive mechanisms between the inputs from different modalities function during the early sensitive period of life in area 7. The aim of the present study was to find out whether further reorganization of functions takes place in the posterior parietal association cortex if monkeys that have experienced binocular visual deprivation through the first year of their life, are allowed to recover from the deprivation for a longer period of time. Four monkeys were deprived of binocular vision after the birth by lid closure for 12 months. Transdural extracellular multiunit recordings were performed in Brodmann's area 7 at the end of the deprivation period after the opening of the eyes. A second set of recordings was conducted in area 7 after a recovery period of 12 months from the deprivation. The results of the recordings at the end of the deprivation period confirmed the already known deprivation effect: there was a reduction in visually responsive neurons, an increase in the representation of somatosensory and somatomotor functions as well as an increase in the amount of cell groups that were 'only spontaneously active'. The recordings performed after the recovery period showed that the representation of visual functions had remained low. However, the amount of 'only spontaneously active' neurons had decreased and the amount of cell groups responding to the monkey's own explorative movements of the hand had further increased. The results indicate that visual deprivation during the early critical period of life results in a profound and persistent reduction of visual functions in area 7. However, activity-dependent competition between inputs from different modalities continue, resulting in the domination of somatosensory and somatomotor functions over visual functions in area 7. The results also suggest that neurons which during the visual deprivation are left without active input from the visual system, gradually become integrated into other functionally active neuronal networks increasing the representation of somatic functions in this cortical area.

Action Potentials↗

PubMedDate not supplied

Effect of sex and age on brain monoamines and spatial learning in rats.

The concentrations of noradrenaline (NA), dopamine (DA), serotonin (5-HT), and their metabolites were measured in the prefrontal cortex, caudate-putamen, and hippocampus in young (3 months) and aged (27-31 months) Wistar rats of both sexes. Age-related changes were found in prefrontal NA and HVA/DA ratio, striatal DA and DOPAC/DA ratio, and striatal and hippocampal 5-HT and 5-HIAA/5-HT ratio. Age and sex dependent changes were found in striatal DA and DOPAC/DA ratio, and hippocampal MHPG-SO4/NA ratio. The aged rats were tested in spatial discrimination and reversal tasks in a T maze. The effects of alpha 2-agonist medetomidine (3 micrograms/kg) on the task performance were assessed in relation to individual variation in monoamine metabolism. Medetomidine impaired spatial discrimination learning of the aged rats by interacting with the hippocampal 5-HT turnover. Medetomidine improved reversal learning through an interaction with the striatal DA turnover and reduced the number of perseverative errors after reversal, mainly due to its interaction with the prefrontal NA turnover. It is concluded that the memory enhancing effect of drugs acting through the brain monoamine systems is highly dependent on the stage of degeneration of these systems that show considerable individual variation in aged animals.

Adrenergic alpha-Agonists↗

PubMedDate not supplied

Effects of metrifonate on the hippocampal theta rhythm of freely moving intact and MS-lesioned mice.

Changes in hippocampal electroencephalogram (EEG) have been suggested to be closely associated with spatial learning ability. Spatial learning can be improved in medial septal (MS)-lesioned mice by metrifonate, a cholinesterase inhibitor. We designed this study to investigate the effects of metrifonate on the hippocampal theta oscillation of intact and MS-lesioned mice. Intact and MS-lesioned C57BL mice were treated with acute injections of metrifonate (doses: 15, 50 and 100 mg/kg ip). These included a dose that considerably improved spatial memory of MS-lesioned mice in our earlier study. In addition, subtype selective muscarinic agents, BIBN-99, AF267B and AF150(S) were used. Recordings of hippocampal theta during movement and awake immobility revealed a dramatic reduction of theta in the lesioned animals. Metrifonate induced prominent changes in the EEG of intact mice, but not of MS-lesioned mice. The effect of metrifonate was not mimicked by two selective M(1)-agonists and was augmented by a combined injection of a selective M(2)-antagonist. These data suggest that improved spatial learning by the cholinesterase inhibitor metrifonate is unrelated to its effects on the hippocampal EEG. These two effects may be mediated through different muscarinic receptor subtypes.

Animals↗

PubMedDate not supplied

Place cell rigidity correlates with impaired spatial learning in aged rats.

In humans and in animals, some aged individuals are severely impaired in learning and memory capacity whereas others perform as well as young adults. In the present study, the spatial memory capacity of young and aged rats was characterized by the Morris water maze task, and then firing patterns of hippocampal "place cells" were assessed as the animals explored a familiar environment and a geometrically-altered version of the environment. Spatial representations of hippocampal cells in young and memory-intact aged rats changed upon exposure to the altered environment. In contrast, spatial representations of many cells in aged, memory-impaired rats were unaffected by the environmental alteration. Furthermore, combining all groups, the extent to which spatial representations distinguished the familiar and altered environments predicted learning capacity in the water maze. These findings suggest that a major component of memory impairment in aging may be the failure of the hippocampus to encode subtle differences in contextual information that differ across multiple experiences, such as the sequence of training trials in the water maze.

Aging↗