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C Acuña

Publications and source records attributed to C Acuña.

13 recordsLinked to original sources
PubMed1992

Cholinergic blockade with scopolamine in adult cats. Effects on the behaviors evoked by apomorphine and amphetamine.

1. The aim of this work is to analyse the role that the cholinergic system could play in the production of the behaviors evoked by apomorphine and amphetamine in adult cats. These two drugs were injected s.c. in separate sessions, before and after a s.c. administration of scopolamine which blocked the muscarinic receptors. The pre and post-scopolamine results of the behaviors produced by the two catecholaminergic drugs were compared using the non-parametric Wilcoxon signed rank test. 2. In a previous step a dose-response study of the behavioral effects of scopolamine, in doses of 0.05, 0.1, 0.4 and 0.8 mg/kg was carried out in ten cats. The Kruskal-Wallis and the non-parametric multiple comparison tests were employed. A dose-dependent decrease in motility (locomotion) and a dose-dependent increase in inappetence and pupillary dilation were found. 3. In thirteen cats which were injected with 2 mg/kg of apomorphine and 2.5 mg/kg of amphetamine the findings were: 1--apomorphine after scopolamine produced a decrease in the hypermotility, compared with the results observed with the former drug previous to scopolamine; 2--with amphetamine an increase in immobility and a decrease in indifference were observed. 4. The authors conclude that the decrease in motility recorded with apomorphine and amphetamine after scopolamine, could be attributed to the proper effect of scopolamine. No explanation could be found for the decrease in indifference found by injecting amphetamine after scopolamine. 5. Considering the antagonistic effect between the dopaminergic and the cholinergic systems and that the latter one has an arousal effect, we postulate that the behavioral indifference produced by apomorphine and amphetamine could be the result of a kind of blockade of the cholinergic system when the catecholaminergic system is activated through the administration of the two cited drugs.

Amphetamine↗
PubMed1992

Responses of visual single cells in the superior colliculus of the albino rat to bright bars.

We studied the responses of 57 visual cells of the superior colliculus of the albino rat to bright sweeping and stationary flashing bright bars to determine the properties of their receptive fields. We observed that 9% (8% in superficial and 11% in deep layers) of the studied cells presented orientation preference and 16% showed direction selectivity (13% in superficial and 22% in deep layers). According to their responses to a flashed bright bar they were classified in OFF-type (19%) and ON-OFF-type (81%). No ON-type cells were found. All cells were driven by the contralateral eye, and only in three cases was single cell activation from the ipsilateral eye possible. Twenty-one per cent (22% in superficial and 18% in deep layers) showed end-stopping when they were tested with bright bars of several lengths.

Action Potentials↗
PubMed1991

Contrast responses to bright slits of visual cells in the superior colliculus of the albino rat.

Contrast is the most effective stimulus in the visual system. The response of single cells to changes in stimulus contrast has been studied in a large variety of animals and the contrast response function determined. In the rat, studies on responses to contrast have been focused primarily in the geniculocortical pathway and there are relatively few in subcortical structures. We report here for the first time the contrast response function of single units located in the superior colliculus (SC) of the albino rat to several stimulus contrast. Cells in the SC require a relatively high contrast to elicit a reliable response and the dynamic response range is restricted to a short contrast interval.

Animals↗
PubMed1990

Lateral-posterior and pulvinar reaching cells--comparison with parietal area 5a: a study in behaving Macaca nemestrina monkeys.

In a previous study we have demonstrated the existence of pulvinar (puv) cells which were optimally activated when a monkey executed reaching movements with his limbs (Acuña et al 1983). We now describe further observations in four Macaca nemestrina monkeys trained to perform goal directed reaching movements aimed at four different positions in space. Extracellular unit activity in the lateralis posterior (lp) and puv nuclei, together with electrooculograms were recorded during the execution of the task. Seven hundred and sixty neurons were studied in the lp-puv complex. One hundred and twenty three cells (16%) showed changes in activity related to the reaching movements. Reaching related cells fell into two categories: goal direction sensitive (28/123 = 23%) and pandirectional (95/123 = 77%). Goal direction sensitive cells showed different responses depending on the direction of the goal relative to the starting point of the movement. The responses of the pandirectional cells were independent of goal direction. The activity of the remaining cells (637/760) could not be correlated with reaching movements. In a smaller number of area 5a (PE) cells (n = 109) studied in one monkey, 82 (75%) were classified as reaching related cells. Of these, 76% (62/82) were goal direction sensitive and 24% (20/82) pandirectional. The lp-puv cells were more dependent on the intentionality of movement than area 5a cells, and not reliably activated by passive manipulation of the limb. After injection of HRP-WGA in area 5a, where the reaching cells were recorded, labeled cells and terminals were located in the lp-puv zones where reaching cells were also found.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Location of neurons projecting to the retina in mammals.

In this study, horseradish peroxidase (HRP) was used as a retrograde tracer in order to investigate the existence of centrifugal pathways to the retina in mammals and to locate the somas of the retinopetal neurons. After the application of HRP to the stump of the cut optic nerve in monkeys, cats, guinea-pigs and rabbits, labeled neurons were located in various areas. The largest number of labeled neurons was found bilaterally in the hypothalamus in the premammillary area, and some neurons were also found slightly more rostral and dorsally towards the posterior hypothalamic area. At the mesencephalic-metencephalic junction, a few labeled neurons were observed in the dorsal raphe nucleus and more ventrally in the tegmental area situated between the medial longitudinal fascicle and the superior cerebellar peduncle. Furthermore, labeled neurons were found in the contralateral medial pretectal area in guinea-pigs, in the ipsilateral tegmental mesencephalic reticular formation in monkeys, in the laterodorsal tegmental nucleus in rabbits, and in the dorsal hypothalamic area near the nucleus of the anterior commissure in monkeys. We were unable to find labeled cells in the dorsal raphe nucleus or in the hypothalamus in rabbits or in the above-mentioned tegmental area in guinea-pigs. These divergences may be due to species differences or may simply be false-negative results due to the known difficulty of using the currently available tracers to label retinopetal neurons.

Animals↗
PubMed1989

Does the pulvinar-LP complex contribute to motor programming?

Extracellular unit recording studies in the pulvinar lateral posterior complex (Pul-LP) of behaving monkeys have shown a response property not previously reported. In monkeys performing aimed arm reaching movements towards frontally located targets some cells showed a change in activity beginning 495 +/- 84 ms before the onset of the reaching movement. This change in frequency precedes that observed in primary motor and parietal posterior cortex for reaching movements. These findings seem to indicate the involvement of the Pul-LP in motor functions and suggest its possible contribution to motor programming.

Action Potentials↗
PubMed1986

Lateral-posterior (LP) and pulvinar unit activity related to intentional upper limb movements directed to spatially separated targets, in behaving Macaca nemestrina monkeys.

We have showed in a previous paper that the pulvinar extracellular unit activity in behaving monkeys was dependent on the attention the animal paid to the stimulus, or on its behavioral significance or on the intentional movements the animal performed. Several groups of pulvinar cells quantitatively studied in the behavioral tasks the monkeys performed were described. "Projection and hand manipulation" neurons belong to a group of pulvinar cells that increased their activity when the animal made an intentional movement of the limb towards an object that attracted his attention. Some of these cells showed temporal patterns of discharge as well as peak rates of activity that frequently differed for reaching movements to spatially separated targets. This suggested that the overall pattern of discharge of these population of cells differ for different directions of arm movements. We give here a description of the observations made in three behaving Macaca Nemestrina monkeys trained to project there hands and arms to four spatially separated targets situated on a panel in front of them and at arm's reach. The extracellular unit activity in the LP-pulvinar was simultaneously recorded during the execution of the behavioral task. Statistical analysis were applied to objectively quantify the electrophysiological data. In 39 microelectrode penetrations, 362 neurons were recorded. 50 cells, a 13 p. 100, showed significative changes in their discharge during the execution of the task. Neurons of this class were activated when the monkey made an intentional movement with his upper limb towards something that attracted his attention. They were driven very poorly, and in a not easily reproducible way by passive manipulation of the limb.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Study of the action of the nucleus accumbens septi electrical stimulation upon the unitary activity of the amygdaloid complex of waking cats.

The extracellular activity of the amygdaloid cells and the action of the NAS stimulation upon them were studied in unanesthetized, non-paralized, waking cats. The neurons were classified according to their responsiveness to olfactory, auditive, visual and behavioural stimuli, and then, the action of the NAS electrical stimulation upon the spontaneous activity of the previously classified cells was studied. The number of cells responding to visual stimuli (projected spot of light, movement) was found to be higher than in previous works. On the other hand, some of the cells activated by behavioural stimulation (presence of rat) behave in a complex manner by changing the characteristics of the response upon modification of its distance from the rat. However the majority of the recorded neurons failed to respond to any of the tested natural stimuli. The existence of rather extensive zones in the amygdaloid complex without spontaneous activity as well as the small number of cells showing modifications of the rate of firing induced by NAS electrical stimulation was remarkable.

Acoustic Stimulation↗
PubMed1978

Defects in accuracy of reaching after removal of posterior parietal cortex in monkeys.

We measured the capacity of monkeys to project the arm to visually located targets under conditions differing in the nature of visual control allowed during reaching. This capacity was impaired by a unilateral posterior parietal lesion which increased the magnitude and variability of errors in projecting the contralateral arm to targets located on either side of the midline. Furthermore, accurate projections of the arm were often accompanied by misorientations of the fingers of the hand. These errors occurred whether reaching with or without visual guidance of the limb. The presence or absence of vision influenced the direction of errors in arm projection. Under conditions permitting a view of the limb and sight of the target, errors occurred in a direction toward the side of the lesion. When all visual cues were eliminated during reaching, errors were directed away from on-target toward the midline as they are in normal monkeys, but were greater in magnitude following the lesion.

Animals↗