Search PubMed⌕ Search

Biomedical subjects

R Romo

Publications and source records attributed to R Romo.

At least 73 records · Page 4Linked to original sources
PubMed1984

Evidence for a dopaminergic innervation of the cat lateral habenula: its role in controlling serotonin transmission in the basal ganglia.

The presence of a dopaminergic innervation of the cat lateral habenula and its possible role in modulating serotonin transmission within the basal ganglia were investigated using both in vitro and in vivo approaches. A high density of [3H]spiroperidol binding sites with similar affinities for domperidone and apomorphine as those present in the cat striatum were found in the habenula. By means of the push-pull cannula technique, a substantial release of [3H]dopamine continuously formed from [3H]tyrosine was detected in the lateral habenula of halothane-anesthetized cats since the amount of [3H]catecholamines was enhanced in the presence of benztropine, an inhibitor of dopamine uptake into dopaminergic nerve terminals. Furthermore, in anesthetized animals with a push-pull cannula implanted in each caudate nucleus and substantia nigra habenular applications of dopamine (10(-7) M) reduced nigral but not striatal release of [3H]serotonin continuously formed from [3H]tryptophan. This change was prevented either by the delivery of domperidone to the lateral habenula or by the blockade of GABAergic transmission (picrotoxin 10(-5) M) in the dorsal raphe. These data support the involvement of habenulo-raphe pathways in the regulation of serotonin transmission in the cat basal ganglia and indicate that dopaminergic inputs to the lateral habenula participate in such a control.

Animals↗
PubMed1984

Distinct commissural pathways are involved in the enhanced release of dopamine induced in the contralateral caudate nucleus and substantia nigra by unilateral application of GABA in the cat thalamic motor nuclei.

The effects of diencephalic or telencephalic commissural sectioning on the changes in [3H]dopamine ([3H]DA) release from nerve terminals (in the caudate nucleus, CN) and dendrites (in the substantia nigra, SN) of the two nigro-striatal dopaminergic pathways induced by the application of GABA (10(-5) M, 30 min) into the left ventralis medialis (VM) or ventralis lateralis (VL) thalamic nuclei were investigated. Experiments were performed in halothane-anesthetized cats implanted with push-pull cannulae in both CN and SN. In unlesioned cats, GABA application into the left VM-VL increased [3H]DA release in both CN and in the contralateral SN confirming previous results. Sectioning of the thalamic massa intermedia only blocked the GABA-induced increase in [3H]DA release in the contralateral SN, the responses in both CN being preserved. Sectioning of the rostral part of the corpus callosum only prevented the GABA-induced increase in [3H]DA release in the contralateral CN, whereas [3H]DA release in the ipsilateral CN and in the contralateral SN was still enhanced. These results suggest that changes in [3H]DA release evoked in both CN and in the contralateral SN by GABA application into the left VM-VL might involve different mechanisms: those observed in the CN result from potent pre-synaptic influences mediated by the bilateral cortico-striatal projections; those induced in the contralateral SN are due to other types of messages involving or passing through the thalamic massa intermedia.

Animals↗
PubMed1984

Effects of electrical stimulation of various midline thalamic nuclei on the bilateral release of dopamine from dendrites and nerve terminals of neurons in the nigro-striatal dopaminergic pathways.

The effects of electrical stimulation of midline thalamic nuclei on the release of [3H]dopamine ( [3H]DA) were determined in both substantiae nigrae (SN) and caudate nuclei of halothane-anesthetized cats using the push-pull cannula method. [3H]DA release was increased in the four structures following stimulation of the interanteromedialis nucleus (IAM) but only enhanced in both SN when nucleus reuniens (RE) was stimulated. In contrast, no effect was detected after delivery of the stimuli to nucleus centralis medialis. These results indicate that the anterior part of the thalamic massa intermedia (IAM and RE particularly) is involved in the bilateral regulation of DA release from nerve terminals and dendrites of the nigro-striatal dopaminergic neurons.

Afferent Pathways↗
PubMed1984

Increased leucocyte histamine release by Entamoeba histolytica antigen in patients with amoebic abscess of the liver.

Leucocytes (basophils) from non-atopic adult subjects living in an area highly endemic with Entamoeba histolytica release histamine in a dose-dependent fashion upon in vitro exposure to an antigen of axenically grown E. histolytica (histolyticin). Leucocytes of patients with acute amoebic liver abscess were significantly more sensitive to this antigen than leucocytes of control subjects, including patients that had recovered from amoebic liver abscess. By comparison Concanavalin-A induced histamine release found in patients with amoebic liver abscess and healthy controls suggest an immunological mechanism for histolyticin induced in vitro histamine release. This is also suggested by the inability of histolyticin to release histamine from leucocytes of healthy newborn infants and the significant fall in sensitivity to histolyticin following incubation of leucocytes in acid pH. Histamine and other mediators may contribute locally to the early intense inflammatory reaction observed in tissue invasion by E. histolytica.

Adolescent↗
PubMed1984

Subcortical correlates of the auditory brain stem potentials in the monkey: bipolar EEG and multiple unit activity responses.

Bipolar EEG and multiple unit activity (MUA) responses correlated to the vertex auditory brain stem potentials (ABSP) were recorded in different brain stem and diencephalic primary auditory pathways and other anatomically related structures of large monkeys under barbiturate anesthesia. Bipolar EEG responses were recorded bilaterally to monaural stimulation and were formed by 3 or more of 6 consecutive components labeled A, B, C, D, E and F (peak latencies of 3.8, 4.2, 4.6, 5.0, 7.8 and 11.8 msec) correlated in latency with waves III, IV, V, VI, VII and SP3 of the ABSP, respectively. Component B was prominent and showed clearcut reverse polarity at the trapezoid body (TB) and superior olivary complex (SOC), while components C and F inverted and everted polarity at the mesencephalic reticular formation (MRF) and medial geniculate nucleus thalami (MG). Subcortical MUA peaks A, B, C, D and E time locked to the stimulus presentation correlated in latency to those of the bipolar EEG responses. In addition, a significant correlation was found between percentage amplitude of the subcortical EEG response components and MUA peaks in different structures contra- (r = 0.847) and ipsilateral (r = 0.973) to the stimulated ear. Although a single wave of the vertex ABSP correlated in latency with more than one response component in different subcortical loci, amplitude of component A was significantly larger (P less than or equal to 0.02) at TB ipsilateral, B at TB and SOC bilateral, and C and F at MRF, and D and E at MG contralateral to the stimulated ear.

Acoustic Stimulation↗
PubMed1983

In vivo release of [3H]GABA in cat caudate nucleus and substantia nigra. I. Bilateral changes induced by a unilateral nigral application of muscimol.

Push-pull cannulae were implanted in both caudate nuclei and both substantiae nigrae (SN) of halothane-anesthetized cats and the release of [3H]GABA, continuously synthesized from [3H]glutamine, was measured in these structures during 4 h of superfusion. In some experiments, multi-unit neuronal activity was recorded at the tip of the nigral push-pull cannulae, using a bipolar electrode. Two hours after the onset of superfusion with [3H]glutamine, 10(-6)M of muscimol was added (for 1 h) in the superfusion medium delivered to one SN. This treatment increased locally the release of [3H]GABA and enhanced the neuronal activity of the nigral cells in the zona reticulata. An increased release of [3H]GABA was also observed in the contralateral SN, in association with an inhibition of the activity of the zona reticulata cells. The unilateral nigral application of muscimol also induced asymmetric changes in the release of [3H]GABA in both caudate nuclei, since [3H]GABA release was increased ipsilaterally and reduced on the contralateral side. The present findings are considered in relation to possible GABAergic neuronal populations affected by this local pharmacological treatment.

Animals↗
PubMed1983

GABA in the thalamic motor nuclei modulates dopamine release from the two dopaminergic nigrostriatal pathways in the cat.

Halothane anesthetized cats were implanted with five push-pull cannulae and the release of (3H)dopamine (3H-DA), newly synthetized from (3H)tyrosine, was measured in both caudate nuclei (CN) and substantiae nigrae (SN). GABA was applied by means of one of the cannula in the ventralis medialis (VM) and the adjacent part of the ventralis lateralis (VL) nuclei of the thalamus. Autoradiographic studies performed with (14C)-GABA showed that the diffusion of the amino-acid in our experimental conditions was restricted to a 4.2 mm3 sphere at the tip of the push-pull cannula. Multi-unit activity was recorded both at the site of GABA injection and in the contralateral VM or VL nucleus. During and after a 30-min application of GABA (10(-5) M) in the VM-VL nuclei, neuronal firing was markedly enhanced locally and decreased in the homologous structures, while (3H)DA release increased in both CN and the contralateral SN. No effect was observed in the ipsilateral SN. These results show that thalamic motor nuclei could play a role in the regulation of the activity of the two dopaminergic nigrostriatal pathways and will be discussed in the light of previous data indicating a role of the thalamus in the bilateral regulation of dopaminergic transmission in the basal ganglia.

Animals↗
PubMed1983

Push-pull perfusion of pentylenetetrazol in the brain stem of 'encéphale isolé' cats.

Nine 'encéphale isolé' cats had 'push-pull' perfusions of pentylenetetrazol (PTZ) in various loci of the brain stem, while the EEG from the right and left motor cortices, EMG from neck muscles, ocular movements and clinical changes were recorded. Perfusions in the rostral MRF induced bilateral rhythmic paroxysmal EEG discharges and myoclonic twitching of neck and head, more prominent in the muscles contralateral to the perfused side. PTZ in the caudal MRF induced tonic-clonic paroxysmal EEG discharges and EMG seizures, similar to those seen when PTZ is injected systemically. Perfusion in the PRF induced EEG spindle bursts, muscular hypotonia and myosis. When perfusion in the MRF inducing rhythmic paroxysmal EEG discharges and myoclonic twitching was followed by perfusion in the PRF, the EEG discharges were not modified, but the myoclonic movements were abolished. Perfusions outside the MRF and PRF did not produce obvious changes other than tonic gaze deviation to the contralateral side or nystagmus. The results suggest that PTZ has a differential effect in various structures of the CNS, producing primary generalized convulsive seizures when acting directly on the MRF.

Animals↗
PubMed1983

Effect of sagittal transections of the brain stem tegmentum on alumina cream-induced focal motor seizures in cats.

The effect of extensive and circumscribed sagittal transections of the brain stem tegmentum on types B (epilepsia partialis continua) and C (contradversive tonic-clonic seizures) alumina cream-induced focal motor seizures in cats was investigated. The neurological abnormalities of cats with transections and differences in the EEG-EMG patterns of types B and C seizures between operated and intact animals were statistically analyzed. Animals with either extensive or superior central nucleus transections showed bilateral neglect and internuclear palsy syndromes, no tonic type C seizures (contradversion), and a significant decrease in electromyogram multiple-unit activity (EMG MUA) from 0 to 10 s or more after the onset of EEG paroxysmal tonic-clonic discharges. Animals with rostral transections showed a unilateral neglect and internuclear palsy or ataxic syndromes with a concomitant partial reduction of contradversive seizures and a significant decrease in EMG MUA from 0 to 5 s or less after the onset of EEG tonic-clonic discharges; those with dorsal and caudal transections showed a transient neglect and insomniac syndromes with no differences in contradversion and EMG MUA at the onset of EEG tonic-clonic discharges in relation to intacts. Experimental and intact animals showed neither differences in types C and B EEG patterns nor in EMG MUA at the end of type C EEG tonic-clonic discharges and type B EEG spikes. These results support the idea that tonic and clonic muscular seizures are due to epileptic impulses originating in the cerebral cortex and mediated at the level of the brain stem by different pathways.

Aluminum Oxide↗
PubMed1983

Effects of unilateral electrical stimulation of various thalamic nuclei on the release of dopamine from dendrites and nerve terminals of neurons of the two nigrostriatal dopaminergic pathways.

The role of several motor and intralaminar thalamic nuclei in the regulation of dopamine release from terminals and dendrites of the nigrostriatal dopaminergic neurons was investigated in halothane-anaesthetized cats. For this purpose, the effects of the unilateral electrical stimulation of various thalamic nuclei on the release of newly synthesized [3H]dopamine were simultaneously determined in both substantiae nigrae and caudate nuclei using the push-pull cannula method. The electrical stimulation of the motor nuclei was the only one to induce asymmetric changes in the four structures since [3H]dopamine release was enhanced in the ipsilateral caudate nucleus and reduced in the contralateral structure while opposite responses were observed in the corresponding substantiae nigrae. A reduction of [3H]dopamine release occurred in the four structures or only in the contralateral substantia nigra and caudate nucleus following the stimulation of the parafascicularis nucleus and the adjacent posterior part of the nucleus centrum medianum or of the nucleus centralis lateralis and the adjacent paralaminar part of the nucleus medialis dorsalis, respectively. The stimulation of the anterior part of the nucleus centrum medianum, which in contrast to other thalamic nuclei examined, receives few nigral inputs, selectively enhanced [3H]dopamine release in the contralateral substantia nigra. No significant changes in [3H]dopamine release were seen either in the substantiae nigrae or in the caudate nuclei following the stimulation of midline thalamic nuclei. These results indicate that the motor and intralaminar thalamic nuclei exert multiple and selective influences on the release of dopamine from terminals and/or dendrites of the dopaminergic neurons. They also further support a role of thalamic nuclei in the transfer of information from one substantia nigra to the contralateral dopaminergic neurons. The possible involvement of connections between paired thalamic nuclei was underlined by the observations of evoked potentials in contralateral homologous nuclei following unilateral stimulation of motor, or some intralaminar, nuclei. The present report provides new insights on the mechanisms contributing to the reciprocal and/or bilateral regulations of nigrostriatal dopaminergic pathways.

Animals↗
PubMed1983

Effects of nigral application of muscimol on release of [3H] gamma-aminobutyrate and on multiunit activity in various cat thalamic nuclei.

The release of [3H] gamma-aminobutyrate (GABA) neosynthesized from [3H]glutamine was estimated in one substantia nigra and in the ipsilateral thalamus of halothane-anesthetized cats by perfusing a [3H]glutamine-enriched physiological medium through a push-pull cannula implanted in the two structures under investigation. After two hours of superfusion, muscimol (10(-6)M) was delivered through the nigral push-pull cannula for 50-60 min and local- and distal-evoked changes of [3H]GABA release were analyzed. In some experiments, changes of global neuronal activity induced by muscimol application were recorded in different thalamic nuclei, using a bipolar electrode. In a few of the above experiments, biochemical and electrophysiological determinations were simultaneously performed in the substantia nigra and the thalamus. The nigral application of muscimol (10(-6)M) induced locally an activation of the substantia nigra reticulata cells, as well as an increase in release of [3H]GABA. Distally, in the thalamus, two types of biochemical and electrophysiological responses were observed according to the localization of the tip of the push-pull cannula or the electrode. (1) An increased release of [3H]GABA and a depression of the global multi-unit cellular activity were obtained in the ventralis medialis-ventralis lateralis, the centralis lateralis and the paracentralis nuclei. These effects could reflect an activation of the GABAergic nigrothalamic neurons projecting to these different thalamic nuclei. (2) In contrast, in the medialis dorsalis paralamellar zone adjacent to the intralaminar nuclei of the thalamus, a decrease of [3H]GABA release and an activation of the multi-unit activity were obtained. These latter results may suggest either a polysynaptic response or the non-GABAergic nature of the nigrothalamic neurons afferent to the medialis dorsalis paralamellar zone.

Animals↗
PubMed1983

GABA in the intralaminar thalamic nuclei modulates dopamine release from the two dopaminergic nigro-striatal pathways in the cat.

Halothane-anaesthetized cats implanted with several push-pull cannulae were used to study the effects of the unilateral application of GABA (10(-5) M, 30 min) into thalamic intralaminar nuclei on the in vivo release of (3H)-dopamine [3H)-DA) newly synthesized from (3H)-tyrosine in both caudate nuclei (CN) and substantiae nigrae (SN). GABA applied into the left centralis lateralis nucleus (CL) elicited symmetric changes in the two CN, (3H)-DA release being initially reduced and thereafter markedly increased. On the contrary, an asymmetric pattern of responses was observed in the two CN during and after GABA application into the left centrum medianum parafascicular complex (CM/PF) since (3H)-DA release was decreased ipsilaterally and enhanced contralaterally. Changes in (3H)-DA release intervening in the two SN appeared to be triggered by processes independant from those operating in the CN. Hence, an immediate increase in (3H)-DA release with a time course distinct from that observed in other structures occurred in the contralateral SN after the application of GABA either into the left CL or the left CM/Pf. Furthermore in both cases, a biphasic response (decrease followed by an increase) similar to that intervening in the CN following GABA application into the CL was seen in the ipsilateral SN. Autoradiographic studies performed with (14C)-GABA (10(-5) M) revealed that the amino-acid did not spread out from the site of application. During and after GABA application (10(-5) M, 30 min) into the CL or the CM/Pf neuronal firing was markedly enhanced not only locally but also into respective contralateral homologous structures. These results further confirm the important and specific roles of distinct thalamic nuclei in the bilateral regulation of DA release from dendrites and nerve terminals of the nigro-striatal dopaminergic neurons.

Animals↗
PubMed1982

Specific and non-specific multiple unit activities during pentylenetetrazol seizures in animals with mesencephalic transections.

A group of cats with brain stem transection at the mesencephalic level was studied during the administration of convulsive doses of pentylenetetrazol in regard to changes in EMG multiple unit activity (MUA), as a method to determine the course of muscular convulsions and their relation with EEG and MUA changes in the motor cortex, pyramidal tract and mesencephalic and pontine reticular formations. PTZ induced significant increase in the duration of EMG tonic convulsions, lasting 3-100 times longer than the entire tonic-clonic seizure seen in intact animals after similar doses of PTZ and not accompanied by EEG or pyramidal tract "seizures", but by an equally long-lasting increase in MUA of mesencephalic and pontine reticular formations. Comparing present results with those seen in intact, "encéphale isolé" and "pretrigeminal" preparations, it is concluded that the mesencephalon is important for both: activating tonic phase of the convulsions and the EEG changes seen in PTZ-induced seizures. It also suggests that termination of seizures is due to inhibitory influences of supramesencephalic structures.

Animals↗
PubMed1982

Effect of dextro-amphetamine on reticulo-preoptic interactions in "encéphale isolé" cats.

Intravenous administration of a single dose of dextro-amphetamine (1 mg/kg) in the "encéphale isolé" cat significantly increased amplitude of the P50 and N110 components of the preoptic potential evoked by the stimulation of the mesencephalic reticular formation and decreased all components of the mesencephalic reticular formation potential evoked by preoptic stimulation. Concomitantly, a state of increased and persistent arousal response was found. These findings support the idea that during wakefulness there is a reticular facilitation and a preoptic inhibition.

Animals↗