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J A Sáez

Publications and source records attributed to J A Sáez.

At least 19 recordsLinked to original sources
PubMed2000

[Evidence for glutamatergic neurotransmission in the geniculo-cortical pathway in the rat].

PURPOSE: To investigate the possible participation of glutamate in the neurotransmission of the rat geniculo-cortical pathway. METHODS: In a first set of experiments, we studied the effects of microiontophoresis of kynurenate, a broad spectrum antagonist of glutamate receptors, on the excitation evoked in visual cortex cells by electrical stimulation of the dorsal lateral geniculate nucleus and the optic tract. Cell activity was determined by extracellular unit recordings. In a second set of experiments, we studied the effects of electrical stimulation of the dorsal lateral geniculate nucleus and the optic tract on the release of glutamate and aspartate in the visual cortex in vivo. Push pull perfusions were made in the visual cortex and the amino acids contents of the perfusates were analysed by high performance liquid chromatography. RESULTS: Microiontophoresis of kynureate in area 17 cells selectively supressed the excitatory response to dorsal geniculate nucleus and optic tract stimulation. On the other hand, stimulation of these structures significantly increased glutamate, but not aspartate, release in area 17. CONCLUSIONS: These results demonstrate that glutamate is the neurotransmitter of the geniculo-cortical pathway in the rat.

Animals↗
PubMed1998

Electrophysiological and neurochemical study of the rat geniculo-cortical pathway. Evidence for glutamatergic neurotransmission.

The projection from the dorsal lateral geniculate nucleus to the primary visual cortex of the rat was studied electrophysiologically. Electrical stimulation of the dorsal lateral geniculate nucleus and the optic tract produced three types of responses on neurons of area 17: excitation followed by inhibition, excitation and inhibition. These results extend and confirm, in adult rats, previous studies done in rat geniculate-visual cortex cocultures preparations in vitro. The role of glutamate in the neurotransmission of the rat geniculo-cortical pathway was also investigated. In a first set of experiments, the effects of kynurenate, an antagonist of glutamate receptors, on visual cortex neurons with a monosynaptic excitatory response to dorsal lateral geniculate nucleus stimulation were studied. Microiontophoresis of kynurenate in area 17 neurons selectively suppressed the excitatory response to dorsal lateral geniculate nucleus and optic tract stimulation. In a second set of experiments, the effects of electrical stimulation of the dorsal lateral geniculate nucleus and the optic tract on the release of amino acids in the rat visual cortex in vivo were studied. Using the push-pull method, we perfused a discrete region of the visual cortex with artificial cerebrospinal fluid (CSF), and the amino acid content of the perfusates was analysed by high performance liquid chromatography (HPLC). Stimulation of either the dorsal lateral geniculate nucleus or the optic tract significantly increased glutamate release in area 17. The rest of the amino acids studied did not show significant changes. The results provide evidence for the participation of glutamate in the neurotransmission of the geniculo-cortical pathway in the rat.

Animals↗
PubMed1998

[Image processing in the primary visual cortex].

INTRODUCTION: Area 17 or the primary visual area forms the first link in the chain of cerebral analysis of a visual image. The neurones forming the primary visual cortex are characterized by the extreme precision of their connections, functional specialization and hierarchic organization. The spatial precision of the connections within the system for vision permit retinotopic representation in the visual cortex, so that each point of the retina is projected into a specific area of the cortex. The cortical neurones which analyze the characteristics of the image situated in a precise zone of the visual field are themselves organized into a basic functional unit known as a hypercolumn. Within each hypercolumn there are various columnar cell systems with receptive fields having similar characteristics. Thus, each hypercolumn is made up of multiple orientation columns, two ocular dominance columns and 'blob' regions. All these systems permit the analysis of different aspects of the image. The neurones belonging to the orientation columns are sensitive to the orientation, spatial frequency and movement of a visual stimulus; those of the 'blob' regions to colour, and the binocular neurones of the ocular dominance columns to depth. Within each column, the hierarchical pattern of neurone interconnections determines the successive appearance of cells with receptive fields having new properties.

Geniculate Bodies↗
PubMed1998

[Psoas muscle abscess. Description of a series of 19 cases].

Abscess of the psoas muscle (PA) is every more frequently observed in recent years. The PA diagnosed in the authors' center over a period of 91 months are presented, analyzing the main clinical features, microbiologic causal agents, risk factors, treatment and the differences between primary and secondary PA. A total of 19 cases of which 14 were secondary PA (73.7%) and 5 primary PA (26.3%) were diagnosed. The main foci of infection of the former were the bone and the genitourinary tract, with intestinal infection being rare. The most frequent clinical data were lumbar pain with possible irradiation to the lower limb, fever, and leucocytosis with neutrophilia. Gram negative and enteric anaerobes were the bacteria most often identified, followed by Staphylococcus aureus and Mycobacterium tuberculosis. In a high percentage of patients (57.8%) a history of immunodeficiency was reported. In regard to treatment, surgical drainage was performed in 5 cases (26.3%), while ten cases (52.6%) were treated by DPCT. Four patients (21%) were exclusively treated with antibiotics. Recurrence was observed in three cases (15.3%) of the DPCT group requiring new drainage. Of all the cases, 18 were cured while one death occurred, being attributed to the underlying tumoral disease of advanced stage. The authors believe DPCT to be a good therapeutic option in both primary and secondary PA, thereby avoiding the risks of major surgery. In the cases with no underlying immunodeficiency the existence of secondary PA should be discarded as occurred in 7 out of 8 cases with no history of immunodeficiency in this series of patients.

Adult↗
PubMed1996

Mediation by neurotensin-receptors of effects of neurotensin on self-stimulation of the medial prefrontal cortex.

1 Intracortical microinjections of neurotensin (NT) selectively decreased intracranial self-stimulation (ICSS) of the medial prefrontal cortex in the rat. 2 To elucidate whether this effect is mediated by NT receptors or by the formation of NT-dopamine complexes, we investigated the effects on ICSS of intracortical microinjections of neurotensin (1-11), an NT fragment that forms extracellular complexes with dopamine but does not bind to NT receptors. 3 We also studied the effects of the peripheral administration of SR 48692, a selective antagonist of NT receptors, on the inhibition of ICSS produced by the intracortical administration of NT. 4 Unilateral microinjections of neurotensin (1-11) at doses of 10, 20 and 40 nmol into the medial prefrontal cortex did not change the basal ICSS rate of this area. 5 The intraperitoneal administration of SR 48692 at doses of 0.08 and 0.16 mg kg-1 30 min before microinjection of 10 nmol of NT into the medial prefrontal cortex, antagonized the inhibition of ICSS produced by the neuropeptide. 6 These results demonstrate that the inhibitory effect of NT on ICSS is mediated by NT receptors.

Animals↗
PubMed1992

Neuromedin N decreases self-stimulation of the medial prefrontal cortex.

Intracerebral microinjections of neurotensin (NT) decrease intracranial self-stimulation (ICSS) of the medial prefrontal cortex (MPC) in the rat. This effect could be due to the ability of NT to bind dopamine. To test this hypothesis we studied the effects of intracerebral microinjections of neuromedin N, a natural NT analogue that does not bind dopamine, on ICSS of the rat MPC. Unilateral microinjections of neuromedin N into the MPC at doses of 2.5, 5, 10, 20 and 40 nmol produced a dose-related decrease in ICSS of the ipsilateral MPC. ICSS of the contralateral MPC, used as a control, was not affected by the microinjections. These results suggest that the inhibitory effect of NT on ICSS is independent of NT-dopamine binding. Because neuromedin N is also present in the MPC, these results also suggest a possible neuromodulatory role of this neuropeptide on ICSS of the prefrontal cortex.

Animals↗
PubMed1991

[Usefulness of captopril as monotherapy and combination therapy in the treatment of arterial hypertension].

The efficacy and tolerance of captopril was prospectively studied as monotherapy for blood hypertension (BH), as well as combined modality with thiazides diuretic and nifedipine as a third drug. 95 cases of BH were followed up for a period of 6 months. 43.15% of the patients who received monotherapy with captopril were controlled (diastolic BP less than 95 mmHg). Those patients who had a diuretic added showed a response of 71.75% and those administered 3 drugs showed a response of 81.25%. The decrease of BH was significant in all groups (p less than 0.01). There was a significant correlation (p less than 0.01) between the response to monotherapy and severity of BH (mild BH 67.50% and severe BH 35.20%). 6.5% of patients abandoned the treatment because of secondary effects. No alterations were noted in the blood test. Monotherapy with captopril is effective in control of mild and moderate BH. In resistant patients, the addition of a diuretic and nifedipine retard as a third drug is useful and well-tolerated in any type of BH severity.

Adult↗