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At least 343 records · Page 19Linked to original sources
PubMed1989

Inspiratory-modulated neurons of the rostrolateral pons: effects of pulmonary afferent input.

In decerebrate, paralyzed cats ventilated with a cycle-triggered pump, firing of inspiratory (I) and I-modulated neurons in the pontine respiratory group was markedly increased by withholding lung inflation, indicating strong inhibition by lung afferents. Spectral analysis showed that only a small minority of I-modulated neurons had high-frequency oscillations (HFO), in contrast to medullary I neurons, indicating that the pontine neurons are not closely linked to medullary I networks.

Action Potentials↗
PubMed1992

Corticotropin-releasing factor mediated muscle atonia in pons and medulla.

The dorsolateral pontine inhibitory area (PIA) and medial medullary reticular formation (MMRF) have been found to mediate the muscle atonia of REM sleep. Our previous studies have shown that acetylcholine (ACh) microinjection in the PIA and in the nucleus paramedianus of the medial medulla produces muscle atonia. Glutamate microinjection in both PIA and nucleus magnocellularis (NMC) of the medial medulla also produces muscle atonia. Since immunohistochemical studies have identified corticotropin-releasing factor (CRF) as a potential dorsolateral pontine and NMC transmitter, the present study was undertaken to determine whether this transmitter could produce suppression of muscle tone. Experiments were performed on unanesthetized, decerebrated cats. CRF was microinjected into points in the PIA and NMC at which electrical stimulation produced bilateral inhibition of muscle tone. We found that CRF produced a dose-dependent muscle tone suppression. At 10 nM concentration, the latency and duration of muscle inhibition produced by CRF injection were comparable with those of L-glutamate, at 18.8 s and 4.1 min, respectively. This CRF-induced muscle inhibition was blocked by the CRF antagonist, alpha-helical [Glu27]corticotropin-releasing factor 9-41 (CRF 9-41). Microinjection of CRF and non-NMDA agonists, kainate and quisqualate, into the same sites in PIA and NMC produced muscle atonia. Pontine sites at which CRF injection induces atonia are identical to those at which acetylcholine microinjection produces atonia. These results indicate that CRF may interact with glutamate and acetylcholine in the generation of muscle atonia.

Animals↗
PubMed1991

Intracerebral grafting of fetal dorsal pons in genetically epilepsy-prone rats: effects on audiogenic-induced seizures.

The present experiments investigated if dorsal pontine tissue obtained from 16-day postconception rat fetuses and stereotaxically transplanted into the dorsal hippocampus or third ventricle of genetically epilepsy-prone rats (GEPRs) would alter the expression of audiogenic seizures. Of eight GEPR-9s receiving pontine-tissue grafts bilaterally into the dorsal hippocampus, none showed any reduction in AGS severity. In contrast, three of five GEPR-9s receiving grafts into the third ventricle eventually displayed a decreased seizure severity following transplantation. Of five GEPR-3s receiving transplants into the hippocampus, one animal showed a gradual and significant reduction in seizure severity after transplantation. Tyrosine-hydroxylase (TH) immunohistochemistry showed that transplanted tissue contained abundant TH-immunoreactive profiles including perikarya and fibers. The results of these preliminary studies suggest that the GEPR model of epilepsy may be useful in studying the corrective potential of neurotransplants.

Acoustic Stimulation↗
PubMed1984

Forelimb and hindlimb stepping by the anesthetized rat elicited by electrical stimulation of the pons and medulla.

This study determined the lower brainstem sites at which electrical stimulation elicits stepping movements of the forelimbs and hindlimbs. Rats (N = 45), anesthetized with nembutal, were fixed in a stereotaxic apparatus so that their limbs contacted a moving treadmill belt. Electrical stimulation (100 microA, 10-sec trains, 0.5-msec cathodal pulses, 50-Hz pulse frequency) was applied every 200 micron through 173 movable electrodes. Well coordinated quadrupedal stepping was elicited by stimulation at dorsal posterior mesencephalic sites including the inferior collicular commissure, the central gray, the nucleus cuneiformis and lateral aspects of the pedunculopontine tegmental nucleus. Caudal and ventral to this general region, sites supporting quadrupedal stepping appeared mainly in or near the spinal trigeminal nucleus. Stepping with only the forelimb and hindlimb contralateral to the stimulation site was associated with the corticospinal tract, the lateral pontis oralis, the lateral pontis caudalis and the ventral reticular nucleus of the medulla. Bilateral forelimb stepping was associated with the trigeminal system and the gigantocellular reticular nucleus. At the level of the rostral medulla, systems involved in bilateral forelimb stepping and contralateral hindlimb stepping appear to be located medially. Systems concerned with bilateral hindlimb stepping appear to be located laterally.

Animals↗
PubMed1983

The contribution of central mechanisms rostral to the pons in high altitude ventilatory acclimatization.

In order to explore the role of suprapontine mechanisms in the ventilatory features of acclimatization to high altitude (HAVA) a study was made of: (a) normal cats after 48 h of exposure to a simulated altitude of 5500 m; (b) those same acclimatized cats 6 h following mid-collicular decerebration; (c) decerebrate cats after 48 h of exposure to a simulated altitude of 5500 m; (d) decerebrate cats after 48 h of exposure to room air at sea level. In a pilot study in which high altitude exposure was maintained for 30 days it was determined that normal cats show all of the manifestations of HAVA after 48 h. These were: increase of VI over acute hypoxic value and a maintained hyperventilation with normoxic inhaled gas; increase of both VT and f, the latter predominantly due to shortened TE; increase of VT/TI. Following decerebration the ventilatory pattern of these cats reverted to the preoperative, acute hypoxic exposure characteristics. Decerebrate cats maintained under normoxic conditions for 48 h showed no changes that were statistically significant, but brief (20 min) hypoxic tests indicated an increase of ventilatory response at the end of the second day. Decerebrate cats maintained for 48 h in the hypoxic environment showed all of the main features of HAVA. We conclude that suprapontine mechanisms in the intact cat exert a facilitatory influence which supports the development of HAVA, but if the structures in which those mechanisms normally reside are chronically removed, a comparable mechanism in the ponto-medullary region is capable of assuming the same function.

Acclimatization↗
PubMed1986

Hydatid cyst of the pons.

A unique case of pontine hydatid cyst is reported. Diagnosis was considered preoperatively on the basis of computed tomographic findings. Needle aspiration and removal of the endocyst were performed through the floor of the fourth ventricle. Postoperative death was due to widespread hemorrhagic infarction of the brainstem. Possible involved mechanisms are discussed.

Adolescent↗
PubMed1989

Epidermoid cyst traversing the pons into the fourth ventricle. Case report.

A rare case of epidermoid cyst traversing the brain stem is presented. Computed tomography revealed the mass within the fourth ventricle; magnetic resonance imaging showed the dumbbell-shaped mass extending from the prepontine cistern to the fourth ventricle. Despite the high mortality and morbidity of brain stem epidermoid cysts in the literature, the tumor was successfully removed. The advantages of magnetic resonance imaging over computed tomography are described.

Adult↗
PubMed1987

Localization of the main noradrenergic neuron groups in the pons and medulla of the rabbit and the importance of cathodal lesions for prolonged survival.

Methods for stereotaxically localizing the major noradrenergic (NA) cell groups (i.e. A1, A2, A5 and A6 + A7) in the rabbit are described. Using a modified Kopf head holder we used surface landmarks including the obex for making lesions of the A1 and A2 cells in the medulla. Localization of the pontine cell groups was done by mapping intracerebral structures including the facial nerve for A5 and the motor nucleus of the trigeminal nerve for A6 + A7. In the initial experiments we made A1 lesions by passing anodal currents through stainless steel electrodes, which was associated with pulmonary oedema, neurological complications and a high mortality. This syndrome was probably related to toxic effects of ferric ion deposition, and disappeared when cathodal currents were employed. We have now made 106 bilateral cathodal lesions in the different groups, with a 20% intraoperative mortality. But virtually all survivors remained indefinitely in clinically good condition for the 2-4 weeks duration of our experiments. In 65 of these rabbits we achieved greater than 75% of NA cell destruction (average 84%). From the cardiovascular viewpoint 'non-specific' damage by the lesions was relatively small, except after A2 lesions where there was some impairment in the baroreceptor-heart rate reflex, though a considerable amount of residual function remained.

Animals↗
PubMedDate not supplied

Precollicular decerebration reduces the pressor responses evoked by stimulation of rostral pons but not medulla in cats.

In 30 cats under chloralose (40 mg/kg) and urethane (400 mg/kg) anesthesia, the ponto-medullary region involved in cardiovascular integration were stimulated by rectangular pulses (0.5 ms, 80 or 5 Hz, 100 to 200 microA) and/or by microinjection of sodium glutamate (Glu, 0.25-0.5 M, 70-200 nl). Changes of systemic arterial blood pressure (SAP) and renal sympathetic nerve activity (RNA) following stimulation were compared before and after precollicular decerebration. Precollicular decerebration itself resulted in an immediate but brief (5 to 15 min) hypotension with a decrease in SAP ranging from 40 to 100 mmHg. Stimulation of the lateral tegmental field (FTL) produced depressor responses. After precollicular decerebration, the stimulation induced depressor responses were either abolished or converted to mild pressor responses. Stimulation of the dorsal gigantocellular tegmental field-periventricular grey (dFTG-PVG) produced pressor responses. These responses were abolished after precollicular decerebration without exception. On the other hand, precollicular decerebration did not reduce pressor responses produced by stimulation of the ventrolateral medulla (VLM) and the dorsal medulla (DM). In 7 additional cats killed with an overdose of pentobarbital, the brain stem were processed for dopamine beta-hydroxylase (DBH). The pressor areas of the VLM and DM were DBH positive, indicating the presence of norepinephrine, while the dFTG-PVG and FTL were not. These findings suggest that the depressor mechanism of the FTL and the pressor mechanism of the dFTG, but not of the VLM or DM depend on actions of the brain structures rostral to superior colliculi.

Animals↗
PubMed1979

Lingual projections to the dorsal pons of the rat, studied by the field potential analysis.

Electrical stimulation of the chorda tympani (CT) of a rat produced a negative field potential with a peak latency of 8 msec localized in the parabrachial nucleus (PB) which may correspond to the pontine taste area. In contrast, stimulation of the glossopharyngeal nerve (GL) gave rise to no detectable negative field potential around the brachium conjunctivum. Stimulation of the lingual nerve (L) produced a large negative field potential with a similar latency, whose focus was found located just lateral to the focus of the negative potentials produced by CT stimulation.

Animals↗
PubMed1986

Vasotocin fibers in the mesencephalon and pons of the domestic fowl. An immunohistochemical study.

Immunohistochemical analysis of the extrahypothalamic distribution of vasotocin-like immunoreactive elements within the brainstem of the domestic fowl revealed several, topographically identifiable, mesencephalic and pontine target areas. In the considered regions numerous nerve endings were surrounding perikarya or large dendritic trunks. No extrahypothalamic immunopositive perikarya have been observed in normal birds.

Animals↗
PubMed1995

Prefrontal cortex projections to the basilar pons in rhesus monkey: implications for the cerebellar contribution to higher function.

The feedforward limb of the cerebrocerebellar system is directed largely through the corticopontine pathway. We determined the extent to which higher order corticopontine projections are derived from prefrontal associative cortices by injecting anterograde tracers into multiple prefrontal regions in rhesus monkeys. Most prefrontopontine projections were derived from the dorsolateral and dorsomedial convexities, including areas 8A, 46 dorsal, 9, and 10; and lighter projections arose from medial and ventrolateral cortices. These findings strengthen the observation that the cerebrocerebellar system incorporates associative cerebral regions, and they enhance the notion that the cerebellum participates in the organization of cognitive function.

Animals↗
PubMed1994

Fos-containing neurons in medulla and pons after unilateral stimulation of the afferent abdominal vagus in conscious rabbits.

Vagal afferents originating in abdominal viscera initiate numerous centrally-mediated responses, including behavioural, cardiovascular and hormonal changes associated with satiety, and nausea and vomiting. The present work was undertaken to map the pontomedullary distribution of neurons expressing Fos immunoreactivity following unilateral electrical stimulation of abdominal vagal afferents in conscious unanaesthetized rabbits. After 2 h of stimulation of the anterior trunk of the abdominal vagus nerve (20 Hz, 0.5 mA, 0.5 ms duration, 4.5 min on, 0.5 min off), Fos-positive neurons were found in the area postrema, the nucleus tractus solitarius, the spinal nucleus of the trigeminal nerve, the caudal and the rostral ventrolateral medulla, the locus coeruleus, the subcoeruleus and the lateral parabrachial nucleus. In all these regions, more than 70% of Fos-containing neurons occurred on the ipsilateral side. In control animals only occasional Fos-immunoreactive neurons were observed, usually very faintly labelled. Simultaneous staining for both Fos and tyrosine hydroxylase revealed Fos immunoreactivity in catecholamine neurons, including A1, A2, C1, A5, subcoeruleus and locus coeruleus (A6) groups. Our findings complement functional studies in the rabbit, identifying A1 neurons as part of the central pathway by which afferent abdominal vagal stimulation increases plasma vasopressin, and C1 neurons as part of the central pathway, whereby afferent abdominal vagal stimulation increase arterial pressure.

Afferent Pathways↗