PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Reticular Formation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6Linked to original sources
PubMed1982

[Microionophoretic analysis of neurons of the reticular formation during food motivation in animals].

Statistical analysis of 40 neurones of the midbrain reticular formation in hungry rabbits has shown that in the animals with food motivation, 50% of the neurones has a specific activity pattern--domination on the interval histogram of interspike intervals within the ranges of 2-10 ms and 100-200 ms characteristic of the hungry animal's status. Microiontophoresis of noradrenaline exerts a specific action on reticular formation neurones, manifesting in the increased number of neurones that react to the application by the enhanced "bundle-formation", i. e. by domination on the histograms of the intervals in the ranges of 2-10 ms and 100-200 ms. Acetylcholine action may cause an analogous distribution of the intervals between neuronal spikes in the hungry animals, although in a less number of neurones but with a more remarkable difference in the peak magnitudes within the ranges of 5-10 and 100-200 ms. Microiontophoretic application of serotonin to reticular formation neurones was found to produce no such an effect.

Action Potentials↗
PubMed1987

Effect of stimulation of the medullary reticular formation on cerebral vasomotor tonus and intracranial pressure.

The authors report the results of a study to evaluate the effect of stimulation of the medullary reticular formation on cerebral vasomotor tonus and intracranial pressure (ICP) after the hypothalamic dorsomedial nucleus and midbrain reticular formation were destroyed. Systemic arterial pressure (BP), ICP, and local cerebral blood volume (CBV) were continuously recorded in 32 cats. To assess the changes in the cerebral vasomotor tonus, the vasomotor index defined by the increase in ICP per unit change in BP was calculated. In 29 of the 32 animals, BP, ICP, and CBV increased simultaneously immediately after stimulation. The increase in ICP was not secondary to the increase in BP, because the vasomotor index during stimulation was significantly higher than the vasomotor index after administration of angiotensin II. The vasomotor index was high during stimulation of the area around the nucleus reticularis parvocellularis. In animals with the spinal cord transected at the C-2 vertebral level, ICP increased without a change in BP. These findings indicate that the areas stimulated in the medullary reticular formation play an important role in decreasing cerebral vasomotor tonus. This effect was not influenced by bilateral superior cervical ganglionectomy, indicating that there is an intrinsic neural pathway that regulates cerebral vasomotor tonus directly. In three animals, marked biphasic or progressive increases in ICP up to 100 mm Hg were evoked by stimulation. The reduction of cerebral vasomotor tonus and concomitant vasopressor response induced by stimulation of the medullary reticular formation may be one of the causes of acute brain swelling.

Animals↗
PubMedDate not supplied

3-Dimensional anatomic relationship of serotonergic and muscarinic receptor binding in the pontine reticular formation of the human infant brainstem.

Cholinergic and serotonergic neurons of the rostral pontine reticular formation have been implicated by animal studies in the modulation of sleep and waking. To define better the spatial relationships between muscarinic and serotonergic receptor binding in the rostral human brainstem, we used 3-dimensional computer reconstructions of serial autoradiographs generated with radioligands to muscarinic and serotonergic receptors. Receptor binding was assessed in a series of 9 human infants, and 3-dimensional reconstructions were performed in a representative infant at 53 postconceptional weeks. The computer reconstructions demonstrated a 3-dimensional distinct pattern in the rostral pontine reticular formation, with high (3H)lysergic acid diethylamide binding to serotonin receptors in the median raphe nucleus flanked by paramedian bands of high (3H)quinuclidinyl benzilate binding to muscarinic cholinergic receptors in the medial nucleus pontis oralis. Based upon comparisons to animal data, we suggest that the muscarinic-serotonergic pattern of receptor binding in the rostral pontine reticular formation represents part of the neurochemical organization of the circuitry involved in the modulation of rapid eye movement (REM) sleep in humans.

Autoradiography↗
PubMed2004

Involvement of the optic tectum and mesencephalic reticular formation in the generation of saccadic eye movements in goldfish.

The circuitry and physiological properties underlying saccadic eye movement generation have been studied mainly in monkeys and cats. By contrast, current knowledge in nonmammalian species is rather scarce. We review here some of our recent findings about the involvement of the optic tectum and mesencephalic reticular formation in the generation of saccades in goldfish. Electrical microstimulation of the optic tectum evokes contraversive saccadic eye movements. In goldfish, as in mammals, the amplitude and direction of saccades are encoded in a spatial topographical map. In addition, there are some areas that have evolved, such as the extreme anteromedial tectal zone, whose activation yields eye convergence. Injections of the bidirectional tracer biotin dextran amine within functionally identified sites of the tectum provide reciprocal, site-dependent connectivity with different downstream structures. Of these structures, the major tectofugal target is the mesencephalic reticular formation. In goldfish, as in mammals, the mesencephalic reticular formation and optic tectum establish reciprocal connections at regional and neuronal levels which support the presence of feedback circuits. Electrical microstimulation demonstrates that the mesencephalic reticular formation can be functionally parceled-the rostral part is linked to vertical saccades, while the caudal part is related with horizontal ones. Finally, these zones are also differently connected to the optic tectum. From these data, we conclude that the involvement of the optic tectum and mesencephalic reticular formation in eye movement generation in goldfish is similar to that reported in cats and monkeys.

Animals↗
PubMed1979

Frequency-following responses in primary auditory and reticular formation structures.

The responses of the cat brain to tonal stimuli were recorded from the inferior colliculus, medial geniculate, reticular formation and the far field. The response consisted of an onset component and a frequency-following response (FFR) component in the inferior colliculus (IC) and the far field. In contrast to previous work, the FFR was also observed in the reticular formation. The response in the reticular formation was abolished at lower doses of pentobarbital and at lower relative intensities of masking than that in the IC and far field. The amplitude of the FFR increased and the latency decreased with progressive ventral movement of the electrode through the IC. The onset component of the response in IC was more easily masked than the FFR component, while the FFR component was depressed to a somewhat greater extent by pentobarbital administration. These findings suggest that the different components of the response to tonal stimuli are generated by different mechanisms.

Acoustic Stimulation↗
PubMed1985

[Effect of novocaine block of limbic system formations of the brain, hypothalamus and reticular formation on evoked potentials in the ventrobasal thalamic nucleus of the rat].

The effect of novocain on evoked potentials (EP) recorded from the ventrobasal complex (VBC) of rats thalamus has been studied during a single pulse stimulation of the contralateral hind paw immobilized with curare. It has been established that significant sinchronized decrease of amplitudes of all the three early components of EP has been observed during the novocain administration in the reticular thalamic nucleus, lateral amygdaloid area and septum. During the blocking of the anterior and posterior hypothalamus the amplitude of the second negative component of EP in VBC decreases, while during the blocking of the dorsal hypothalamus an increase of the amplitudes of all the three early components of EP is mainly observed.

Afferent Pathways↗
PubMed1977

[Typology of the cells of the bulbopontine reticular formation].

The network analysis methods have been applied to study the neurons of the medial bulbo pontine reticular formation in the cat. The bifurcation ratio allows isolation of two different cellular patterns: collateral branched cells or CB type, and at random pendant vertices dichotomously branched cells or DA type. The morphologic features of CB cells lead to the assumption that these cells have an integrative function. The topographic distribution of the two cells types seems to vary in the different parts of the reticular formation and should argue for the fact that the reticular formation represents an aggregation of several discrete anatomical units.

Animals↗
PubMed1982

Ocular accommodation in the cat after electrical stimulation of mesencephalic reticular formation.

We measured ocular accommodation in the cat with a continuously recording infrared optometer. The brain stem reticular formation in an anesthetized cat was stimulated electrically with microelectrodes to evoke accommodation. Sites in the mesencephalic reticular formation caudal and ventral to the III nerve nucleus near the midline gave large positive accommodation responses. The velocity and amplitude of postive accommodation was graded, depending on the applied current and frequency of stimulation. Relaxation of accommodation proceeded at a fairly constant rate upon cessation of electrical stimulation. These findings provide new information on the amplitude and dynamic aspects of ocular accommodation in the cat. Also, the location of the stimulating electrodes suggest that in addition to the Edinger-Westphal nucleus, areas in the mesencephalic reticular formation between the cerebellum and the oculomotor nucleus are involved in ocular accommodation in the cat.

Accommodation, Ocular↗
PubMed1986

Are there connections between the thalamic reticular nucleus and the brainstem reticular formation?

Increasing awareness that the thalamic reticular nucleus (TRN) plays an important role in controlling the output of cortically projecting cells in nuclei of the dorsal thalamus has focused attention on the question of whether there exist ascending projections to the TRN from the mesencephalic or other parts of the brainstem reticular formation (BRF). We have examined this and the related question of whether the neurons of TRN project to the BRF, by anterograde and retrograde tracing experiments with horseradish peroxidase (HRP) and HRP conjugated to wheat germ agglutinin. Injections of tracer were placed stereotaxically in the BRF at various depths and rostrocaudal and mediolateral coordinates, and the TRN and adjacent nuclei were examined in serial coronal sections, using tetramethylbenzidine as the principal chromogen. Retrogradely labelled cell bodies were consistently seen in hypothalamus and zona incerta but never in TRN, suggesting that, in the rat, TRN neurons do not project caudal to the thalamus. After 54 out of 60 injections, no terminal label was detected in any part of the TRN although such label was present in other parts of the thalamus, including the intralaminar nuclei, in the same sections. We therefore conclude that direct projections from the BRF to the TRN must be extremely sparse, and that those effects of BRF stimulation upon thalamocortical transmission that are mediated by the TRN (rather than by direct projections to dorsal thalamic nuclei) probably depend chiefly on indirect polysynaptic pathways.

Animals↗
PubMed1993

Connections between the pontine reticular formation and rostral ventrolateral medulla.

Pontine reticular formation (PRF) neurons provide tonic excitatory drive to sympathetic nerves and are involved in cardiovascular control [K. Hayes and L. C. Weaver. Am. J. Physiol. 263 (Heart Circ. Physiol. 32): H1567-H1575, 1992]. However, connections between the PRF and the well-known vasomotor region in the rostral ventrolateral medulla (RVLM) are unknown. In propofol (Diprivan)- anesthetized rats we investigated arterial pressure, heart rate, and renal nerve responses to microinjection of glycine (1.0 M, 60 nl) into the PRF before and after injection of the synaptic blocking agent cobalt chloride (4.0 mM, 200 nl) into the RVLM. Glycine injections into the PRF caused decreases in arterial pressure, heart rate, and discharge of renal sympathetic nerves. Synaptic blockade of the RVLM almost eliminated cardiovascular and sympathetic responses to glycine injections into the PRF and blocked somatosympathetic reflexes in the renal nerve. Cobalt injections into the RVLM had very small effects on basal renal nerve firing, arterial pressure, or heart rate. These results suggest that the neurons within the RVLM relay influences from the PRF to sympathetic preganglionic neurons. Because injections of the excitatory amino acid antagonist, kynurenate, into the RVLM also interrupted responses to blockade of the PRF and blocked somatosympathetic reflexes, glutamate is a likely neurotransmitter from the PRF to the RVLM and for somatosympathetic reflexes.

Animals↗
PubMed1988

Vertical eye movements related signals in antidromically identified medullary reticular formation neurons in the alert cat.

Short and long lead burst neurons antidromically activated from the rostral mesencephalic reticular formation, and synaptically activated from the contralateral superior colliculus were recorded in the medullary reticular formation underlying the prepositus hypoglossi nucleus. These neurons were shown to be related to vertical eye movements, ranging from pure vertical to oblique planes. Vertical saccade coding was similar to that of horizontal short lead pontine cells. The presence of vertical short and long lead burst neurons in the medullary reticular formation raises new questions about the organization of the control of eye movements in the vertical plane.

Action Potentials↗
PubMed2002

[Study on the change of bFGF in reticular formation of medulla oblongata after primary brain-stem injury].

OBJECTIVE: To study the effect of primary brain-stem injury on the expression of basic fibroblast growth factor (bFGF) in the reticular formation of medulla oblongata. METHODS: Immunohistochemical SABC was used to study the change of bFGF expression in the reticular formation of medulla oblongata after brain-stem injury by striking. RESULTS: The numbers of positive cells and positive intensity of the study group in the reticular formation of medulla oblongata were significantly elevated than those of the control group and the postmortem injury group. CONCLUSION: The expression of bFGF is elevated in reticular formation after brain-stem injury.

Animals↗
PubMed1976

Relations of single semicircular canals to the pontine reticular formation.

The effects of afferent vestibular impulses on single pontine reticular formation units and on a small filament of the IIIrd cranial nerve were recorded with tungsten microelectrodes in 40 curarized guinea pigs. Single-shock and repetitive electrical stimulations were applied by means of stimulating electrodes inserted bilaterally into the perilymphatic space of single ampullae of the anterior and lateral semicircular canals. The reticular unitary response consisted mainly in excitation of the resting discharge rate: most units showed vestibular convergence being affected by separate stimulation of the single four ampullae. the reticular evoked field and unitary potentials accounted for latency values ranging from 0.3 to 2.5 msec. As for the early latencies they can be interpreted as responses mediated by direct vestibulo-reticular fibres. A delimited vestibular projection field in the parameidan pontine reticular formation was not identified.

Animals↗
PubMed2006

Propofol, more than halothane, depresses electroencephalographic activation resulting from electrical stimulation in reticular formation.

BACKGROUND: Halothane and propofol depress the central nervous system, and this is partly manifested by a decrease in electroencephalographic (EEG) activity. Little work has been performed to determine the differences between these anesthetics with regard to their effects on evoked EEG activity. We examined the effects of halothane and propofol on EEG responses to electrical stimulation of the reticular formation. METHODS: Rats (n= 12) were anesthetized with either halothane or propofol, and EEG responses were recorded before and after electrical stimulation of the reticular formation. Two anesthetic concentrations were used (0.8 and 1.2 times the amount needed to prevent gross, purposeful movement in response to supramaximal noxious stimulation), and both anesthetics were studied in each rat using a cross-over design. RESULTS: Electrical stimulation in the reticular formation increased the spectral edge (SEF) and median edge (MEF) frequencies by approximately 1-2 Hz during halothane anesthesia at low and high concentrations. During propofol anesthesia, MEF increased at the low propofol infusion rate, but SEF was unaffected. At the high propofol infusion rate, SEF and MEF decreased following electrical stimulation in the reticular formation. CONCLUSIONS: At immobilizing concentrations, propofol produces a larger decrease than halothane in EEG responses to reticular formation stimulation, consistent with propofol having a more profound depressant effect on cortical and subcortical structures.

Anesthetics, Inhalation↗
PubMed1986

Involvement of the midbrain reticular formation in self-injurious behavior, stereotyped behavior, and analgesia induced by intranigral microinjection of muscimol.

Bilateral microinjection of muscimol (60 ng), a gamma-aminobutyric acid (GABA) agonist, into the central region of the substantia nigra (pars reticulata) produced self-injurious behavior (SIB), stereotyped behavior and analgesic-like effects in rats. Bilateral electrolytic lesions of the midbrain reticular formation ventrolateral to the periaqueductal gray matter completely blocked the SIB but had little effect on stereotyped behavior produced by intranigral muscimol. Lesions of the midbrain reticular formation reduced the antinociceptive effect of intranigral muscimol on the tail-flick but not on the hot-plate test. Bilateral microinjection of muscimol (10-100 ng) into the midbrain reticular formation produced intense stereotyped behavior and had an analgesic-like effect on the hot-plate test but not on the tail-flick test. Stereotyped behavior appeared to interfere with the paw-lick response on the hot-plate test. These data suggest that the antinociceptive effect of intranigral muscimol on the tail-flick test is mediated by fibers that project to or pass through the midbrain reticular formation and that analgesia may play an important role in muscimol-induced SIB. The midbrain reticular formation does not appear to be involved in the stereotyped behavior produced by intranigral muscimol.

Animals↗
PubMed1983

Long collateral branches of substantia nigra pars reticulata axons to thalamus, superior colliculus and reticular formation in monkey and cat. Multiple retrograde neuronal labeling with fluorescent dyes.

In order to gain some impressions about the degree to which individual neurons of the pars reticulata of the substantia nigra send long collateral branches to more than one of its three major targets (thalamus, superior colliculus, reticular formation), two, or all three targets were injected with fluorescent dyes (Evan's blue, granular blue, nuclear yellow, propidium iodide) in six squirrel monkeys and four cats. The best results were obtained in the monkey brain with injections of Evan's blue in the thalamus, granular blue in the colliculus and nuclear yellow in the reticular formation. Whereas nigrothalamic and nigroreticular neurons are numerous and widely scattered throughout all parts of the pars reticulata, cells projecting only to the superior colliculus are fewer in number and restricted to a rostral-lateral zone. These results are consistent with earlier data obtained with the horseradish peroxidase method. Although double-labeled cells with projections to both the thalamus and reticular formation occur throughout the pars reticulata, such cells are somewhat more abundant at caudal levels of the nucleus. Cells containing dyes from both the superior colliculus and reticular formation are less common and restricted to the lateral part of the pars reticulata. A small number of cells near the rostral pole of the pars reticulata contain dye from both the tectal and thalamic injection. Typically, less than two dozen cells in any case can be confidently identified as containing all three dyes and these cells are located in the rostrolateral half of the pars reticulata. Fewer than 20% of the labeled nigral cells contain more than one dye. In the cat, thalamic injection of granular blue and tectal injection of nuclear yellow indicate that most nigrotectal cells are located in the middle of the mediolateral expanse of the pars reticulata in its rostral half. Nigrothalamic cells flank the nigrotectal group medially, laterally and caudally. Where these groups border one another, several cells contain both dyes indicating that they project to both the thalamus and colliculus. In both the cats and monkeys, a less extensive cell-labeling occurs in the contralateral nigra with a pattern similar to that in the ipsilateral substantia nigra. The results indicate that several neurons of the substantia nigra's pars reticulata send long collateral branches to two or even all three of the major targets. Many reticulata cells, however, appear to project either to the thalamus, or to the superior colliculus or to the reticular formation.

Animals↗