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E Motles

Publications and source records attributed to E Motles.

At least 37 records · Page 2Linked to original sources
PubMed1987

Evidence for a nigro-pulvinar-lateralis posterior complex projection in the cat using horseradish peroxidase neuronal retrograde technique.

The possible existence of a direct projection from the substantia nigra to the pulvinar-lateral posterior complex (Pul-LP) was investigated in the cat by using the horseradish peroxidase technique. In particular horseradish peroxidase was injected in the Pul-LP of 8 animals, either unilaterally or bilaterally. Tissue sections obtained from the cat's brain 24-48 hrs. after injection were prepared according to Mesulam's method as slightly modified by the authors. Retrogradelly labelled neurons were observed in substantia nigra pars lateralis and reliculata ipsilaterally to the injected pulvinar-lateral posterior complex. A small number of labelled cells were also found in the contralateral substantia nigra. These findings demonstrate the existence of a close connection between two system which are involved in turning behavior: the nigrostriatal and the pulvinar-lateral posterior complex-superior colliculus.

Animals↗
PubMed1986

The head-eye-body turning behavior induced by electrical or cholinergic stimulation of the pulvinar-lateralis posterior nucleus complex is not dependent on the catecholaminergic system.

Two experimental designs were developed in cats in order to analyze the role of the catecholaminergic system in the turning response evoked by cholinergic or electrical stimulation of the pulvinar-lateralis posterior nucleus complex (P-LP). Twenty one adult cats were employed. In one series of experiments, nine cats had a cannula implanted in one P-LP, and through it, apomorphine alone or mixed with carbachol were microinjected. The behavior was observed and the EEG was recorded. In the second experimental design, a cannula and bipolar electrodes were implanted unilaterally in the P-LP of nine cats, and a series of electrical stimulations were performed before and after 6-OHDA administration into the P-LP, and apomorphine was injected parenterally in order to induce turning behavior. Finally three cats received 16 micrograms of 6 OHDA into the P-LP, through a Hamilton syringe and no electrodes or cannula were implanted, to study the histological damage. No evidence of involvement of the catecholaminergic system was found in either of these two experimental series. These results contrast with what has been found in the nigrostriatal dopaminergic system, where an imbalance in dopamine concentration induces turning behavior. High doses (16 micrograms) of 6-OHDA induced minimal damage in the P-LP.

Animals↗
PubMed1986

Electrophysiological projections of pulvinar-lateralis posterior complex (P-LP) upon superior colliculus units in the cat.

The effect of Pulvinar-Lateral Posterior (P-LP) electrical stimulation on superior colliculus unitary responses and eye movements is analyzed in 17 encéphale isolé cats. Twelve of them were curarized. Out of a total of 190 recorded units, 117 were localized in the superior colliculus and 73 units in the Mesencephalic Reticular Formation (MRF) below the superior colliculus. Thirty eight per cent (n = 45) of the collicular units modified their discharge frequency when the ipsilateral P-LP was electrically stimulated. The current intensity thresholds of transynaptic activation had a range between 0.5 and 2.0 mA. Most of the orthodromic responses were produced by ipsilateral P-LP stimulation and were localized in the intermediate and deep layers of the superior colliculus. Three types of responses were obtained: short latency responses between 2 and 10 ms (57%); intermediate latency responses between 15 and 40 ms (29%), and long latency responses between 50 and 200 ms (14%). Thirty one per cent (n = 18) of the units recorded in the MRF responded to P-LP stimulation with 10 ms pulse-trains duration. In the MRF 3 types of responses were observed: 1) a decrease or blockade in the resting discharge during 20 to 100 ms after stimulation (20%); simple responses with a latency between 25 and 150 ms (40%), and complex responses with an early response and a latency between 15-40 ms, and a late response with a latency between 150 and 200 ms (40%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

[Role of the pulvinar lateralis posterior complex on the rotation response. Relation with other cerebral structures. Pharmacological systems involved in this behavior].

A critical analysis of the results obtained in four experimental series of cats is presented. In these experiments the following results are shown: 1) Electrical stimulation of the pulvinar-lateral posterior nucleus complex (P-LP) evokes a contralateral turning of the head accompanied by similar directional rotation of both eyes, most of them of the saccadic type. With higher intensity currents contralateral circling is produced. 2) The motor output of the P-LP is through the ipsilateral superior colliculus. Electrolytic lesion of this last structure suppresses the turning behavior induced by electrical stimulation of the P-LP. The same result is not obtained when the ipsilateral caudate nucleus, or the nucleus centralis lateralis of the thalamus are lesioned. 3) The ablation of the ipsilateral cerebral cortex having important reciprocal connections with P-LP, produces in 50% of the cats studied, in the first week after the ablation, a suppression of the turning response. However at 30 days after the surgical procedure, 86% of the electrodes implanted in P-LP are able to induce a turning response by electrical stimulation. 4) The local injection into P-LP, through a cannula, of carbachol or dioxolane (an exclusive muscarinic receptor activator) produces also contralateral head-eye-body turning response. We postulate the P-LP as another structure related to turning, different from the nigro-striatal system. This last one is not affected by lesioning of the superior colliculus, as happens with the P-LP. On the other hand, the main putative neurotransmitter involved in the nigro-striatal system is dopamine, whereas in P-LP is probably acetylcholine.

Animals↗
PubMed1985

Morpho-functional effects of kainic acid injection into the cat's pulvinar-lateralis posterior nucleus complex.

The histological, electroencephalographic, behavioral changes as well as the changes in the intensity threshold of stimulation necessary to induce contralateral turning were studied in 16 cats, in which kainic acid (KA) was injected locally into the pulvinar-lateralis posterior nucleus complex (P-LP). In 13 cats a stainless-steel tube with two attached electrodes was implanted in P-LP, and electrodes were also implanted in the ipsilateral dorsal hippocampus, the superior colliculus and the caudate nucleus. KA was injected through the tube using a 10 microliters Hamilton syringe. In other 3 cats, KA was injected stereotaxically through the needle of the Hamilton syringe and two electrodes were implanted in these areas after withdrawal of the syringe. The intensity thresholds of stimulation required to induce turning behavior were controlled before and after KA administration in the 13 cats with an implanted tube and only after KA injections in the three cats without a tube; in these instances the current threshold of the contralateral P-LP served as control. The histological results showed a moderate KA damage of the P-LP, with destruction of neuronal soma and gliosis and additional involvement, in all the experiments, of the dorsal hippocampus; however, passage fibers were spared by the lesions. A dose-dependent epileptic effect of KA was seen, which was slight with the 3 micrograms dose and intense with 6 micrograms. The EEG recording showed a prominent and almost simultaneous epileptic involvement of the hippocampus and the P-LP after KA, with less involvement of the other implanted structures. Turning behavior induced by electrical stimulation of the P-LP was suppressed when the electrode tip was located inside the lesioned area. When the electrode tip was placed inside a slight or moderate damaged tissue, a significative increase in current threshold was found, and finally when the tip of the electrode was outside the lesioned area no change in threshold was observed. These findings do not contradict our previous hypothesis of an intrinsic cholinergic mechanism involved in the turning response evoked by P-LP electrical stimulation, although it cannot be excluded that fibers coming presumably from the superior colliculus or pretectum may contribute to the response.

Animals↗
PubMed1985

Role of the pulvinar-lateralis posterior nucleus complex (P-LP) in the experimental epilepsy of the cat.

The ability of the pulvinar-lateralis posterior nucleus complex (P-LP) to evoke epileptic activity when stimulated, was studied in 20 adult cats. Twelve animals were analyzed after they recovered from the surgical procedure (chronic model). In seven of them a cannula with electrodes was implanted in the P-LP and one twisted bipolar electrode was placed ipsilaterally in the following structures: hippocampus, superior colliculus, caudate nucleus and cerebral cortex. Through the cannula Na penicillin was injected. The electrodes allowed both to stimulate and to record the electrical activity. In the remaining five cats, the cannula was implanted in hippocampus in order to compare its sensitivity to generate epileptic activity to that of P-LP. Another group of eight cats were surgically implanted and studied in the same day (acute model). In four of them the cannula was placed in the P-LP through the temporal pathway, to avoid crossing the hippocampus and the ventricle. In another four, penicillin was injected in the P-LP after suctioning the cerebral cortex and the hippocampus overlying the former structure. Epileptic activity could be induced in P-LP and it spread rapidly to hippocampus and after a while to the other implanted structures. This was observed both with penicillin and electrical stimulation. The sensitivity of P-LP to generate epileptic activity was lower than that of the hippocampus. In particular, it was necessary to use two to ten times more penicillin and three times the electrical current intensity in the P-LP as compared to the values needed in the hippocampus. These results are discussed in view of the controversial problem about the ability of the thalamus to generate and spread epileptic activity.

Animals↗
PubMed1984

Motor effects of electrical and cholinergic stimulation of the cat's dorsal hippocampus.

The effect of electrical stimulation of the dorsal hippocampus was studied in 17 adult cats with implanted electrodes and those effects of carbachol and dioxolane in a group of ten adult cats with a cannula and electrodes implanted in the above cited structure. Electrical stimulation induced a contralateral head-eye-body turning response in 3 cats (17.6%), only when it was associated with afterdischarge. On the other hand the cholinergic agonists evoked contralateral head-eye-body turning in nine out of ten cats in whom the injections were administered into the hippocampus. The fact that dioxolane, an exclusive muscarinic agonist evoked this behavior and that atropine sulfate blocked this response, favours the postulation that turning is due to activation of muscarinic receptors inside the dorsal hippocampus. Comparison was done between the hippocampal group with a group similarly studied with electrodes implanted in the pulvinar-lateralis posterior nucleus complex (P-LP), and in the caudate nucleus, in which the electrical stimulation evoked contralateral head-eye-body turning response without any EEG activation.

Animals↗
PubMed1983

A pharmacological analysis of autonomic pathways mediating myocardial disturbances originating in a lateral hypothalamic area of the cat.

A study was made of the mechanisms mediating autonomic changes resulting from stimulation of a site in the lateral hypothalamic area (LHA). This site, when stimulated, induced angina-like ECG disturbances similar to those observed in some cases of brain traumas. These ECG changes were often associated with other autonomic changes, such as pressor response, tachycardia (in some cases bradycardia), nictitating membrane (NM) contraction and pupillary dilatation. Most symptoms were sympathetic: they were largely abolished by spinal cord section between C1 and C2, but were not affected by vagotomy, except that bradycardia was converted to tachycardia. Adrenal catecholamines were not involved since adrenal vein ligation was without effect. Hexamethonium (5-10 mg/kg) prevented pressor response and tachycardia in most cats but only partly protected against ECG changes and NM contractions. Atropine methyl nitrate (0.2 mg/kg) abolished the remaining ECG abnormalities and NM tension. The beta-receptor antagonists, propranolol and practolol (50 micrograms/kg) completely prevented the ECG changes induced either by isoprenaline or LHA stimulation. It is concluded that the symptoms induced by LHA stimulation result from noradrenaline release in the target organs.

Angina Pectoris↗
PubMed1983

Rotational behavior in the cat induced by electrical stimulation of the pulvinar-lateralis posterior nucleus complex: role of the cholinergic system.

We studied the involvement of the cholinergic system in the contralateral head-eye-body turning induced in the cat through stimulation of the pulvinar-lateralis posterior nucleus complex (P-LP). In 17 cats through a cannula aimed at the P-LP, agonists and antagonists of the cholinergic system were injected. The electrical activity of the P-LP could be recorded through the same cannula or through electrodes attached to it. In addition, electrodes were implanted ipsilaterally in the dorsal hippocampus, caudate nucleus, amygdala, and superior colliculus to record through them and through one screw placed on the skull the electrical activity of those structures and of the cortical P-LP projection. Seven days after surgery, carbachol, an agonist of the cholinergic system was injected in the P-LP, and the behavior and electrical activity of the unrestrained cat (previously accustomed to a plastic cage) were recorded. A control volume of 0.9% NaCl was always injected previously. The usual drug volume injected was 1 microliter; occasionally, 2 microliter were injected. Weekly or biweekly sessions were conducted to determine (a) the threshold for cholinergic activation, (b) the threshold for turning behavior, (c) the blocking effect of local atropine sulfate injected previously, (d) the effect of haloperidol previously injected (locally or systemically), and (e) the effect of dioxolane, an exclusive muscarinic agonist. In 14 of 17 cats, contralateral turning behavior was evoked by carbachol. In two of the three cats that did not respond to carbachol, dioxolane induced turning. The effect of dioxolane was similar to that of carbachol when tried in five cats. Besides turning behavior, carbachol produced numerous symptoms due to cholinergic activation. Atropine blocked the rotational effect of carbachol in all cats, and haloperidol blocked it in 68% of them. Electrolytic coagulation of the dorsal hippocampus surrounding the P-LP did not disturb the effects induced by carbachol. These experiments show that both systems of the P-LP, cholinergic and catecholaminergic, are involved in the contralateral turning. We conclude that the effect induced by carbachol is due to activation of muscarinic receptors because it is totally blocked by local atropine sulfate and is reproduced by dioxolane, an exclusive muscarinic agonist.

Acetylcholine↗
PubMed1983

Effects of cortical ablations on the turning response evoked by stimulation of the pulvinar-lateralis posterior nucleus complex in the cat.

The role played by the cerebral cortex on turning responses elicited by electrical stimulation of P-LP was studied in 9 chronic cats. In three animals the sensorimotor cortex was bilaterally ablated and the threshold values for inducing a turning response were determined. None of the cats showed abnormal threshold values. In six cats the cerebral cortical area known to have reciprocal anatomical connections with P-LP was unilaterally removed. Seven days after surgery, 50% of the electrodes gave no responses; 25% evoked responses with high thresholds and 25% with normal thresholds. One month after surgery the percentages were: 14, 18 and 68 respectively. Histological findings show important fiber and neuronal degeneration in P-LP. It is postulated that this area of the cerebral cortex plays, a facilitatory role on the P-LP ability to induce turning response and that the recovery of this ability can be explained by the development of P-LP denervation supersensitivity.

Animals↗
PubMed1982

Local electrographic effects of leu-enkephalin microinjections into the brain.

Microinjections of Leu-enkephalin were made in dorsal hippocampus, caudate nucleus, amygdala, nucleus accumbens and parietal cortex in rats. The effects of enkephalin on the local electrical activity recorded from the area of the microinjection are described. Depression effects (attenuation of amplitudes and slowing) were recorded in caudate nucleus, nucleus accumbens, amygdala and parietal cortex, but not in hippocampus. Activation and epileptiform effects (spikes, seizures) were recorded from all structures studied.

Animals↗
PubMed1982

Effects of subcortical electrolytic lesions on the head-eye turning response induced by electrical stimulation of the cat's pulvinar-lateralis posterior nucleus complex.

The relations between three subcortical structures and P-LP, all of them capable of inducing contralateral head-eye turning responses when electrically stimulated, were studied in three groups of cats. In all the experiments stainless steel electrodes were chronically implanted in P-LP and in each group of five cats. Electrodes were also placed respectively in the caudate nucleus, superior colliculus and nucleus centralis lateralis. Series of current intensity threshold values for evoking head-eye turning responses were determined in each group, before and after electrolytic lesion of these three subcortical structures. The total observation period was approximately 30 days. Only the destruction of the superior colliculus produced the loss of the ability of the ipsilateral P-LP to evoke turning response. According to these results it is postulated that the efferent pathway that carries the information for turning response from P-LP runs through the ipsilateral superior colliculus.

Animals↗
PubMed1981

Influence of body temperature on the epileptogenic effect of enkephalin microinjections into the hippocampus.

The influence of different body temperatures on the epileptiform discharges induced in hippocampus by local microinjections of leu-enkephalin was studied in rats. In the absence of enkephalin, changes in body temperature by either cooling or heating induced epileptiform discharges that disappeared after temperature stabilization. The epileptiform episode induced by enkephalin microinjections was of longer duration at temperature below normal (29-30 degrees C). At body temperature above normal (39-40 degrees C) the epileptiform discharge was less intense and of shorter duration. In vitro testing led to parallel results: the destruction of enkephalin by the brain tissue was faster at higher temperatures. It is proposed that in conditions of hyperthermia enkephalin has a weaker activity due to acceleration of the activity of peptidases involved in its breakdown.

Animals↗