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 469 records · Page 26Linked to original sources
PubMed2000

GABA in the deep layers of the superior Colliculus/Mesencephalic reticular formation mediates the enhancement of startle by the dopamine D1 receptor agonist SKF 82958 in rats.

GABA transmission in the deep layers of the superior colliculus/deep mesencephalic reticular formation (deep SC/Me) mediates several motor responses, including those expressed after systemic administration of dopamine agonists. In the present study we examined the role of the deep SC/Me in the modulation of the acoustic startle reflex and its enhancement by the dopamine D(1) agonist SKF 82958. Rats were implanted with bilateral cannulas into the deep SC/Me or superficial layers of the SC (super SC) and 1 week later were infused with various compounds. The GABA(A) antagonist bicuculline (0, 5, and 10 ng) produced a dose- and time-dependent enhancement of startle after infusion into the deep SC/Me, but not the super SC. Infusion of the GABA(A) agonist muscimol (0.1 microg) into the deep SC/Me, but not the super SC, blocked the enhancement of startle by systemic SKF 82958 (1 mg/kg) but had no effect on baseline startle by itself. This effect was not produced by infusion of the D(1) antagonist SCH 23390(1 microg) or the glutamate antagonist NBQX (0.1 microg). Deposits of FluoroGold into the deep SC/Me, combined with immunohistochemistry for glutamic acid decarboxylase (GAD), confirmed a direct GABAergic input from the substantia nigra pars reticulata (SNr) to the deep SC/Me. These results suggest that GABA tone in the deep SC/Me modulates the expression of startle as well as the enhancement of startle by dopamine D(1) agonists. On the basis of these data and previous work, we have proposed a striatonigral-tectal-reticular neural pathway mediating the effects of dopamine D(1) agonists on startle.

Acoustic Stimulation↗
PubMedDate not supplied

Participation of the reticular formation of the mesencephalon in the development of habituation to visceral influences.

In experiments on cats anesthetized with chloralose and immobilized with flaxedil, the influence of the reticular formation (RF) of the mesencephalon on the development of habituation of evoked potentials (EP) in the cerebral cortex (CC) to repeated stimulation of the splanchnic nerve was studied. It was established that high frequency stimulation of the RF (100 counts/sec) for 15 sec before testing for habituation to visceral stimulation inhibited the amplitude of the EP and shortened the time of development of habituation to repeated stimulation of the splanchnic nerve. Low-frequency stimulation of the RF (1 pulse/sec), applied during the development of habituation, restored the amplitude of the EP to the initial level. The turnoff of the activity of the RF by intravenously injected chlorpromazine (3-6 mg/kg) was accompanied by an acceleration of the development of habituation of evoked potentials in the associative region of the cortex. The participation of the RF in processes of habituation and dehabituation is discussed.

Animals↗
PubMed1985

The morphology of trigeminal nociceptive neurons in the caudal bulbar lateral reticular formation of the cat.

Two types of trigeminal nociceptive neurons, i.e. subnucleus reticularis ventralis (SRV) and wide dynamic range (WDR) neurons were identified in the caudal bulbar lateral reticular formation (LRF) and intracellularly stained with horseradish peroxidase. SRV neurons were large neurons characteristic of the subnucleus reticularis ventralis. Their dendrites were confined to the LRF. WDR neurons were situated in the subnucleus reticularis dorsalis. Their dendrites penetrated into the magnocellular layer, but did not reach the substantia gelatinosa.

Animals↗
PubMed1983

Dose effects of morphine on the spontaneous unit activity recorded from the thalamus, hypothalamus, septum, hippocampus, reticular formation, central gray, and caudate nucleus.

Spontaneous activity was recorded from 652 units in 8 subcortical structures of unanesthetized rats. Recordings were obtained in central gray, mesencephalic reticular formation, parafasciculus thalami, caudate nucleus, anterior and ventromedial hypothalamus, lateral septum, and dorsal hippocampus. Eighty recordings were obtained from untreated animals and 80 from saline-injected controls, none of which showed any significant changes of unit activity during the 4- 5-hr observation period. The effect of morphine, given in 5 incremental doses from 0.5 to 30.0 mg/kg ip, was followed in 492 units. Morphine enhanced or depressed spontaneous discharge rates, or caused biphasic effects, ie enhancement alternating with depression and vice versa. Naloxone induced increase in firing after either effect of morphine, or reduced spontaneous activity after morphine-induced increases. However, when morphine reduced neuronal discharges, naloxone never caused further depression. In 86 units, morphine at any dosage failed to alter neuronal activity, but in 54 of these units naloxone nevertheless induced alterations in firing rates. The pattern of responses to morphine differed between all 8 brain regions examined and was characteristic for each individual structure. This is the first systematic study describing the dose-response characteristics of morphine in 8 brain sites recorded simultaneously. Furthermore, it utilized freely behaving animals without the interference of anesthetics, which are themselves known to interact with opiates. The variety of response patterns seen supports the neuropharmacological evidence for multiple opiate receptors or multiple sites of opiate action.

Animals↗
PubMed1990

Thalamic afferents from the brain stem. An experimental study using retrograde single and double labelling with HRP and iron-dextran in the rat. I. Medial and lateral reticular formation.

The reticulo-thalamic projection of the rat was studied in single and double experiments using 51 injections of HRP and/or iron-dextran. The medial reticular formation (excluding the ncl. pedunculo-pontinus, subncl. compactus, see Part II) sends out projections to the ncll. intralaminares (IL), ncl. mediodorsalis (MD), ncl. ventralis medialis (VM), ncl. ventralis lateralis (VL), ncl. ventralis basalis (VB) and ncl. posterior (PO) of the thalamus. The mesencephalic RF (ncl. cuneiformis and ncl. subcuneiformis) projects to all the above mentioned nuclei. The rhombencephalic RF (ncl. pontis oralis, ncl. pontis caudalis, ncl. gigantocellularis et paragigantocellularis dorsalis et lateralis) projects to the posterior IL (ncl. parafascicularis and ncl. centromedianus) and to the MD, pars paralaminaris. The pontine RF (ncl. pontis oralis et caudalis) projects to the posterior IL and to the medial part of the ncl. parafascicularis. The RF of the pons and the upper oblongata projects to the VL, VB and PO. The lateral RF (ncl. parvocellularis) projects solely from the tiers around the ncl. n. VII. to the posterior IL in what is a scanty projection. We found no connections projecting from the medial or lateral RF to the midline nuclei, to the lateral nuclei or to the ncl. commissurae posterioris; the projection to the ncl. reticularis thalami was left unstudied. The reticulo-thalamic pathways exhibit marked laterality. The mesencephalic RF projects to the thalamus in what is pronounced ipsilateral predominance, the pontine RF in ipsilateral predominance, the upper oblongata RF equally ipsi- and contralaterally, and the lower oblongata RF with a predominance of the contralateral component. Collateralization (double labelled cells) was found projecting solely to the IL and MD regions. It was both ipsilateral and contralateral. The discoveries included the topographical organization of the reticulo-thalamic projection: a major antero-posterior in the rhombencephalon and a mediolateral in the projections from the mesencephalon and from the pons. The most substantial projection was found aiming at the posterior IL nuclei (ncl. parafascicularis-centrum medianum), a less substantial one to the ventral and posterior nuclei, and the scantiest to the anterior IL nuclei (ncl. paracentralis, ncl. centralis lateralis).

Animals↗
PubMed2000

Effects of reversible inactivation of the primate mesencephalic reticular formation. II. Hypometric vertical saccades.

Electrical microstimulation and single-unit recording have suggested that a group of long-lead burst neurons (LLBNs) in the mesencephalic reticular formation (MRF) just lateral to the interstitial nucleus of Cajal (INC) (the peri-INC MRF, piMRF) may play a role in the generation of vertical rapid eye movements. Inactivation of this region with muscimol (a GABA(A) agonist) rapidly produced vertical saccade hypometria (6 injections). In three of six injections, there was a marked reduction in the velocity of vertical saccades out of proportion to saccade amplitude (i.e., saccades fell below the main sequence). This was associated with a moderate increase in saccade duration. Inadvertent inactivation of the INC could not account for these observations because vertical, postsaccadic drift was not observed. Similarly, pure downward saccade hypometria, the hallmark of rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) inactivation, was always preceded by loss of upward saccades in our experiments. We also found a downward and ipsiversive displacement of initial eye position and evidence of a contraversive head tilt following piMRF injections. Saccade latency was shorter after two of six injections. Simulation of a local feedback model provided three possible explanations for vertical saccade hypometria: 1) a shift in the input to the model to request smaller saccades, 2) a reduction of LLBN input to the vertical saccade medium lead burst neurons (MLBNs), or 3) an increase in the gain of the feedback pathway. However, when the second hypothesis was coupled to a shortened duration of the saccade trigger (i.e., the discharge of the omnipause neurons), the physiological observations of piMRF inactivation could be replicated. This suggested that muscimol had targeted structures that provided both long-lead burst activity to the MLBNs in the riMLF and were critical for reactivation of the omnipause neurons. Evidence of markedly reduced vertical saccade amplitude, curved saccade trajectories, increased saccade duration, and saccades that fall below the amplitude/velocity main sequence in these monkeys closely parallels the oculomotor findings of patients with progressive supranuclear palsy (PSP).

Animals↗
PubMed1992

Non-dopaminergic neurons in the substantia nigra project to the reticular formation around the trigeminal motor nucleus in the rat.

The dorsolateral part of the substantia nigra (SN) of the rat was observed to send projection fibers to the reticular formation (RF) around the trigeminal motor nucleus (Vm), bilaterally with a clear-cut ipsilateral dominance, by the anterograde and retrograde tracing techniques with PHA-L and WGA-HRP. A combination of retrograde tracing and immunohistochemistry for tyrosine hydroxylase (TH) revealed that no SN neurons sending their axons to the RF around the Vm showed TH-like immunoreactivity.

Animals↗
PubMed1976

Effects of stimulation of the midbrain reticular formation upon thalamo-cortical neurones responsible for cortical recruiting responses.

1. In lightly nembutalized cats, effects of high frequency (60-100/sec) repetitive stimulation of the midbrain reticular formation (RF) were tested upon the thalamo-cortical (T-C) neurones which project from the anterior ventral (VA) nucleus of the thalamus and its vicinities to the parietal association cortex and convey impulses responsible for cortical recruiting and spindling-like responses. 2. Tonic maintained or rhythmic grouped firings of the T-C neurones recorded as extracellular units with microelectrode in the thalamus were in the majority suppressed by high frequency RF stimulation during and often for a short time after the stimulation, and they showed later tonic discharges for many seconds or minutes. Intracellular recording from the T-C neurones revealed hyperpolarizing potential changes corresponding to the suppression on high frequency RF stimulation. Field potential analysis in the VA nucleus indicated that the hyperpolarization is ascribed at least in part to IPSPs elicited in the T-C neurones. Responses in some other types of thalamic neurones to the RF stimulation were exemplified to be compared and related with those of the T-C neurones. 3. Desynchronization of the parietal electrocorticogram coincided with the suppression of the T-C neurones and lasted for the time of the later tonic discharges, which contrasted with the rhythmic grouped discharges of the T-C neurones in association with recruiting and spindling-like responses of the cortex. Relations between the thalamo-cortical recruiting system and the ascending reticular activating system were discussed.

Animals↗
PubMed1999

M2 muscarinic receptor subtype in the feline medial pontine reticular formation modulates the amount of rapid eye movement sleep.

Rapid eye movement (REM) sleep is generated, in part, by activating muscarinic cholinergic receptors (mAChRs) in the medial pontine reticular formation (mPRF). Molecular cloning has identified five mAChR subtypes, and this study tested the hypothesis that the M2 subtype in the mPRF modulates the amount of REM sleep. This hypothesis cannot be tested directly, due to lack of subtype selective muscarinic agonists. However, the amount of REM sleep can be enhanced by mPRF microinjection of a muscarinic agonist, and the relative potencies of muscarinic antagonists to block the REM sleep enhancement can be determined. Two muscarinic antagonists, methoctramine and 4-DAMP, were studied. Six concentrations of each antagonist were microinjected into the mPRF of conscious cat 15 min prior to the agonist bethanechol. Nonlinear regression analysis was used to calculate the dose of antagonist that caused a 50% inhibition (ID50) of bethanechol-induced REM sleep. Bethanechol significantly increased (442%) the amount of time spent in REM sleep. Both methoctramine and 4-DAMP significantly blocked the bethanechol-induced REM sleep increase, with an ID50 of 1.8 microM and 0.6 microM, respectively. The ID50 ratio for methoctramine-to-4-DAMP (3.0) was similar to the affinity ratio of methoctramine-to-4-DAMP only at the M2 subtype (3.5), suggesting that the M2 subtype in the mPRF modulates the amount of REM sleep. This study also tested the null hypothesis that sleep-dependent respiratory depression evoked by mPRF cholinomimetics would not be antagonized by pretreatment of the mPRF with muscarinic antagonists. Neither methoctramine nor 4-DAMP antagonized the bethanechol-induced decrease in respiratory rate.

Animals↗
PubMed1993

Neurons in the superficial dorsal horn of the rat spinal cord projecting to the medullary ventrolateral reticular formation express c-fos after noxious stimulation of the skin.

The nociceptive nature of the neurons of the superficial dorsal horn (laminae I-III) which project to the medullary ventrolateral reticular formation is studied in the rat. Medullary injections of Fluoro-Gold showed exclusive retrograde labeling of laminae I-III cells when the tracer filled a zone intermediate between the lateral tip of the lateral reticular nucleus and the spinal trigeminal nucleus, pars caudalis. This zone is here called VLMlat. Following noxious mechanical or thermal stimulation of the skin, double-labeled neurons, which stained retrogradely and were Fos-immunoreactive, prevailed in laminae I and IIo. Double-labeled neurons were few in lamina IIi after thermal stimulation and entirely lacking in lamina III after the two kinds of stimulation. Findings in lamina I confirm previous electrophysiological data (see Menétrey et al., J. Neurophysiol., 52 (1984) 595-611) showing that lamina I cells projecting to the ventrolateral reticular medulla convey noxious messages. The occurrence of numerous double-labeled cells in lamina IIo suggests that this lamina is also involved in nociceptive transmission to the VLMlat.

Animals↗
PubMed1995

Demonstration of axon collateral projections from the substantia nigra pars reticulata to the superior colliculus and the parvicellular reticular formation in the rat.

It was revealed in the rat that single neurons in the substantia nigra pars reticulata (SNr) innervated both the superior colliculus (SC) and the parvicellular reticular formation (RFp) in the pons and medulla oblongata by way of axon collaterals. After injecting Fluoro-gold into the lateral part of the SC and Fluoro-ruby into the RFp on the same side, some SNr neurons were double-labeled with both tracers. They were localized in the dorsolateral part of the caudal half of the SNr ipsilateral to the injection sites.

Animals↗
PubMed1978

[Recording of human eye movements in cases of unilateral lesions of the paramedian pontine reticular formation (author's transl)].

Clinical observation of two cases with a particular type of Foville's syndrome appears to confirm physiological data from many experimental studies on the paramedian pontine reticular formation (PPRF). The nature of the oculomotor syndrome, which was confirmed by electrooculographic recordings, together with the analysis of pathognomonic features, suggested the existence of limited unilateral pontine lesions involving the formation. Rather than relying on subtle differences in ocular reflex signs it should be noted that each PPRF produces all homolateral saccades and controls pursuit eye movements in both directions, though only in the homolateral hemifield of eye movements.

Adult↗
PubMed1991

Release of acetylcholine and GABA, and activity of their synthesizing enzymes in the rat pontine reticular formation.

The aim of this study was to obtain neurochemical information on the possible role of acetylcholine (ACh) and gamma-aminobutyric acid (GABA) as neurotransmitters in the pontine reticular formation (PRF). We studied the uptake of labeled choline and GABA, as well as the release of this amino acid and of ACh, in PRF slices of the rat. In addition, choline acetyltransferase, acetylcholinesterase and glutamate decarboxylase activities were assayed in PRF homogenates. The uptake of GABA was strictly Na(+)-dependent, whereas choline uptake was only partially Na(+)-dependent. The release of both ACh and GABA was stimulated by K(+)-depolarization, but only the former was Ca(2+)-dependent. Choline acetyltransferase activity in the PRF was 74% of that in the striatum, whereas acetylcholinesterase activity was considerably lower. Glutamate decarboxylase activity in the PRF was about half that observed in the striatum. These findings support the possibility that both ACh and GABA may act as neurotransmitters in the rat PRF.

Acetylcholine↗
PubMed1999

Vasoactive intestinal polypeptide excites medial pontine reticular formation neurons in the brainstem rapid eye movement sleep-induction zone.

Although it has long been known that microinjection of the cholinergic agonist carbachol into the medial pontine reticular formation (mPRF) induces a state that resembles rapid eye movement (REM) sleep, it is likely that other transmitters contribute to mPRF regulation of behavioral states. A key candidate is the peptide vasoactive intestinal polypeptide (VIP), which innervates the mPRF and induces REM sleep when injected into this region of the brainstem. To begin understanding the cellular mechanisms underlying this phenomenon, we examined the effects of VIP on mPRF cells using whole-cell patch-clamp recordings in the in vitro rat brainstem slice. VIP directly depolarized cells via activation of an inward current; these effects were attenuated and potentiated in low-sodium and low-calcium medium, respectively. The depolarization induced by VIP was slower in onset and longer-lived than that evoked by carbachol. The VIP-induced depolarization was reduced in a dose-dependent manner by a competitive antagonist of VIP receptors. Effects of VIP were attenuated in the presence of guanosine 5'-O-(2-thiodiphosphate, 2'5'dideoxyadenosine, and PKI15-24 and were nonadditive in the presence of 8-bromo-cAMP. We conclude that VIP excites mPRF neurons by activation of a sodium current. This effect is mediated at least in part by G-protein stimulation of adenylyl cyclase, cAMP, and protein kinase A. These data suggest that VIP may play a physiological role in REM induction by its actions on mPRF neurons.

Animals↗
PubMed1997

Arm-movement-related neurons in the primate superior colliculus and underlying reticular formation: comparison of neuronal activity with EMGs of muscles of the shoulder, arm and trunk during reaching.

Neuronal activity was recorded from the superior colliculus (SC) and the underlying reticular formation in two monkeys during an arm reaching task. Of 744 neurons recorded, 389 (52%) clearly modulated their activity with arm movements. The temporal activity patterns of arm-movement-related neurons often had a time course similar to rectified electromyograms (EMGs) of particular muscles recorded from the shoulder, arm or trunk. These reach cells, as well as the muscles investigated, commonly exhibited mono- or biphasic (less frequently tri- or polyphasic) excitatory bursts of activity, which were related to the (pre-)movement period, the contact phase and/or the return movement. The vast majority of reach cells exhibited a consistent activity pattern from trial to trial as did most of the muscles of the shoulder, arm and trunk. Similarities between the activity patterns of the neurons and the muscles were sometimes very strong and were especially notable with the muscles of the shoulder girdle (e.g. trapezius descendens, supraspinatus, infraspinatus or the anterior and medial deltoids). This high degree of co-activation suggests a functional linkage, though not direct, between the collicular reach cells and these muscles. Neuronal activity onset was compared with that of 25 muscles of the arms, shoulders and trunk. The majority of cells (78.5%) started before movement onset with a mean lead time of 149+/-90 ms, and 36.5% were active even before the earliest EMG onset. The neurons exhibited the same high degree of correlation (r=0.97, Spearman rank) between activity onset and the beginning of the arm movement as did the muscles (r=0.98) involved in the task. The mean neuronal reach activity (background subtracted) ranged between 7 and 193 impulses/s (mean 40.5+/-24.2). The mean modulation index calculated [(reach activity background activity)/reach activity+background activity)] was 0.75+/-0.23 for neurons (n=358) and 0.87+/-0.14 for muscles (n=25). As the monkeys fixated the reach target constantly during an arm movement, neuronal activity which was modulated in this period was not related to eye movements. The three neck muscles investigated in the reach task exhibited no reach-related activity modulation comparable to that of either the reach cells or the muscles of the shoulder, arm and trunk. However, tonic neck muscle EMG was monotonically related to horizontal eye position. The clear skeletomotor discharge characteristics of arm-movement-related SC neurons revealed in this study agree with those already known from other sensorimotor regions (for example the primary motor, the premotor and parietal cortex, the basal ganglia or the cerebellum) and are consistent with the possible role of this population of reach cells in the control of arm movements.

Animals↗
PubMed1975

[Effects of stimulating the caudal zones of the mesencephalic reticular formation on the postcruciate cortex of the cat].

The influence of the electrical stimulation of the dorsolateral (DL) and the ventromedial (VM) portions of the caudal area of the mesencephalic reticular formation on the neuronal activity of the lateral zone of the gyrus sygmoideus posterior was investigated in cats. The mesencephalo-cortical influences were mainly excitatory in character; the predominance of the neuronal reactions with a short latency (3--12 msec) during the VM stimulation and reactions with a longer latency (20--25 msec) during the DL stimulation was revealed. The VM and the DL were found to influence both cortical neurones, the ones sensitive to somesthetic stimuli (mono-, di- and polyvalent) and the ones which failed to respond to the electrocutaneous stimulation of the limbs.

Animals↗
PubMed1987

Collateralization of frontal eye field (medial precentral/anterior cingulate) neurons projecting to the paraoculomotor region, superior colliculus, and medial pontine reticular formation in the rat: a fluorescent double-labeling study.

Paired injections of fluorescent tracers (True Blue, Diamidino-Yellow) were made into the oculomotor complex (OMC) and medial pontine reticular formation (mPRF), and superior colliculus (SC) and mPRF, in adult rats to retrogradely label the cortical cells of origin of projections to these oculomotor-related brainstem structures. While large numbers of single-labeled cells in the medial frontal cortex projected only to the mPRF, the presence of many double-labeled cells in the dorsomedial shoulder cortex (medial precentral/anterior cingulate areas), the rat frontal eye field (FEF), indicated that this cortical region contains lamina V pyramid neurons whose axons collateralize to project to the region of the OMC, SC, and mPRF. The similarities of rat and monkey FEF connections, and their relevance to the control of eye movement, are discussed.

Animals↗