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At least 289 records · Page 16Linked to original sources
PubMed1991

Activity of spinal trigeminal pars oralis and adjacent reticular formation units during differential conditioning of the rabbit nictitating membrane response.

Spinal trigeminal nucleus pars oralis (SpoV) is anatomically linked to brain circuitry thought to subserve unconditioned and conditioned nictitating membrane responses in rabbit. Single-unit recording from SpoV and adjacent reticular formation obtained during conditioning from awake, behaving animals revealed modulation of unit firing related to CS, US, and CR occurrence. SpoV participates directly in the unconditioned response and probably relays US information to other brain areas subserving conditioning. The presence of CR-related activity suggests that SpoV may participate in the CR motor output pathway, and may also provide CR-related information to cerebellum. Sensory convergence and CR-related activity in reticular formation mark this structure as a candidate locus of primary neuronal plasticity in this example of conditioning.

Acoustic Stimulation↗
PubMed2001

Role of the medial medullary reticular formation in relaying vestibular signals to the diaphragm and abdominal muscles.

Changes in posture can affect the resting length of respiratory muscles, requiring alterations in the activity of these muscles if ventilation is to be unaffected. Recent studies have shown that the vestibular system contributes to altering respiratory muscle activity during movement and changes in posture. Furthermore, anatomical studies have demonstrated that many bulbospinal neurons in the medial medullary reticular formation (MRF) provide inputs to phrenic and abdominal motoneurons; because this region of the reticular formation receives substantial vestibular and other movement-related input, it seems likely that medial medullary reticulospinal neurons could adjust the activity of respiratory motoneurons during postural alterations. The objective of the present study was to determine whether functional lesions of the MRF affect inspiratory and expiratory muscle responses to activation of the vestibular system. Lidocaine or muscimol injections into the MRF produced a large increase in diaphragm and abdominal muscle responses to vestibular stimulation. These vestibulo-respiratory responses were eliminated following subsequent chemical blockade of descending pathways in the lateral medulla. However, inactivation of pathways coursing through the lateral medulla eliminated excitatory, but not inhibitory, components of vestibulo-respiratory responses. The simplest explanation for these data is that MRF neurons that receive input from the vestibular nuclei make inhibitory connections with diaphragm and abdominal motoneurons, whereas a pathway that courses laterally in the caudal medulla provides excitatory vestibular inputs to these motoneurons.

Abdominal Muscles↗
PubMed1994

Distribution of serotonin cells projecting to the pontomedullary reticular formation in the cat.

Using immunohistochemistry and retrograde transport techniques, this study demonstrates that serotonin (5-HT) cells in the dorsal tegmental gray of the pons at rostrocaudal from P1 to P6 levels are sources of bilateral serotonergic projections to the gigantocellular tegmental field of the medial pontine and medullary reticular formation in the cat. The cells observed were a relatively homogeneous population of small (30 microns) to medium-sized (40 microns) cells, oval, fusiform or spindle-shaped. Rostrally and caudally located 5-HT cells in the dorsal tegmental gray tended to project to the pontine and medullary reticular formation respectively. The dendrites of these cells spread in a plane perpendicular to the long axis of the brainstem. Thin 5-HT fibers with a series of fine varicosities (0.5-1.0 microns in diameter) surrounded reticular neurons, and some of these varicosities closely apposed the proximal dendrites and somata of the reticular neurons. Both large (50 microns) and small (20-30 microns) reticular neurons were uniformly innervated by 5-HT fibers. As revealed in the present study, the serotonergic system, together with the monoaminergic and cholinergic systems, seems to be involved in behavioral state regulation.

Animals↗
PubMed1983

Intracellular evidence linking medial pontine reticular formation neurons to PGO wave generation.

Intracellular recordings in the medial portion of the pontine reticular formation in the gigantocellular tegmental field and the tegmental reticular nucleus of the naturally sleeping cat have indicated the presence of a class of neurons whose discharges have a long lead time (50-300 ms) prior to, and a high correlation with primary ponto-geniculo-occipital (PGO) waves in the lateral geniculate nucleus (LGN) ipsilateral to the recording site; we term these neurons long lead PGO wave positive neurons. Further correlative evidence for their being a part of the circuitry generating PGO waves was their discharge suppression prior to the occurrence of secondary PGO waves in the ipsilateral LGN, and the presence of a contralateral inhibitory input that may explain the occurrence of PGO waves with lateralized amplitude characteristics.

Animals↗
PubMed1988

Effects of pontomedullary reticular formation stimulation on the neuronal networks responsible for rhythmical jaw movements in the guinea pig.

1. In the ketamine-anesthetized guinea pig, electromyographic (EMG) responses of the digastric muscle and vertical and horizontal movements of the mandible were studied when loci within the caudal pontine and rostral medullary reticular formation were stimulated during rhythmic jaw movements (RJMs) evoked by stimulation of the masticatory area of the cortex. 2. Within these regions electrical brain stem stimulation of the pontis nucleus caudalis and nucleus gigantocellularis (PnC-Gi) of the reticular formation completely blocked RJMs at stimulus intensities as low as 10 microA while suppressing the short-latency digastric EMG response that was time locked to each cortical stimulus in the train. PnC-Gi stimulation did not, however, reduce the excitability of the short-latency corticotrigeminal excitatory pathway to digastric motoneurons when tested by short pulse train stimulation at 2 Hz (3 pulses, 500 Hz, 0.3 ms) in the absence of RJMs. 3. Short trains (80 ms) of PnC-Gi stimuli delivered at various phases of the RJM cycle produced a permanent phase shift of the RJM rhythm. If the stimulus train was delivered at an early phase of the cycle (8-40%) the next cycle onset was advanced; if the train was delivered later in the cycle (60-80%) the next cycle onset was delayed. Long trains of PnC-Gi stimuli (100, 200, 300, and 400 ms) increased the time of onset of the next cycle by an amount directly proportional to the duration of the stimulus train. 4. Digastric EMG activity occurring during cortically evoked RJMs occupied nearly 50% of the cycle. If a short train of PnC-Gi stimuli was delivered between approximately 5 and 125 ms after the onset of the burst, the duration of the burst was significantly shortened. 5. These results demonstrate that the suppression of cortically evoked RJMs resulting from PnC-Gi stimulation is due to direct effects on central circuits responsible for the production of the RJM behavior and not on the motoneurons themselves. The evidence presented is consistent with our previously presented hypothesis that the neurons involved in mediating the short-latency corticotrigeminal pathway to digastric motoneurons are separate and distinct from those neurons comprising the central networks responsible for the production of the fundamental jaw oscillation during RJMs.

Animals↗
PubMed1985

Gudden's tegmental nuclei and their connections to the hypothalamus and the reticular formation. II. An experimental study using retrograde double labelling with HRP and iron-dextran in the rat.

12 rats in double experiments were studied for the simultaneous retrograde transport of HRP and Dextran-fer from injections in the mamillary body and in the reticular formation or in selected diencephalic structures into the cells of Gudden's tegmental nuclei. The results of this particular study corroborated the findings of retrograde transport in single experiments (see Part I) showing all the cells of ventral Gudden's nucleus as projecting into the mamillary body, the cells of its peripheral parts as projecting also via a collateral to the lateral hypothalamus, and the cells of its central parts as projecting, in addition, via a collateral to the reticular formation (ncl. pedunculo-pontinus and ncl. pontis oralis). Cells of the ventral part of the ncl. dorsalis tegmenti Guddeni project into the lateral mamillary body and some of then also through a collateral into the whole of the hypothalamus. Part of its cells project independently into the RF (ncl. pontis oralis). The dorsal part of the ncl. dorsalis tegmenti Guddeni projects bilaterally to the ncl. pontis oralis.

Animals↗
PubMed2002

The caudal medullary ventrolateral reticular formation in nociceptive-cardiovascular integration. An experimental study in the rat.

The endogenous pain control system is composed of multiple functionally distinct brain regions, which are thought to integrate nociceptive information with various brain functions. The clear involvement of some pain control centres in cardiovascular modulation has been claimed as a strong indication of their role in nociceptive-cardiovascular integration. Particular emphasis has been given to their putative function in triggering cardiovascular reactions to pain. However, the possibility of their participation in the less-studied influence of cardiovascular conditions in pain perception has been largely ignored. We have recently addressed this issue by investigating the involvement of the caudal ventrolateral medullary reticular formation (cVLM) in hypertension-induced hypoalgesia. Circuits capable of conveying cVLM-elicited antinociception include a direct reciprocal cVLM-spinal loop, and two disynaptic spinal pathways relaying in rostroventromedial medullary (RVM) neurones and A(5) noradrenergic neurones. In the three pathways, the cVLM neurones involved are circumscribed to a small area of reticular formation located laterally to the lateral reticular nucleus, the VLMlat. The VLMlat has a vasodepressor effect similar to that obtained from the cVLM. In the spinal cord dorsal horn, c-fos expression evoked by noxious stimuli is decreased in hypertensive animals, as compared to normotensive animals. In hypertensive animals following lesion of the VLMlat, spinal c-fos expression is identical to that observed in normotensive animals. The collected data point to a role for the VLMlat in the depression of spinal nociceptive processing in response to rises in blood pressure. Since hypertension-induced hypoalgesia is mediated by spinal alpha(2)-adrenoreceptors, this effect could be conveyed by the cVLM-A(5)-spinal pathway.

Animals↗
PubMed2003

Isoflurane action in spinal cord indirectly depresses cortical activity associated with electrical stimulation of the reticular formation.

UNLABELLED: Anesthetics act in the spinal cord to ablate both movement and the ascending transmission of nociceptive information. We investigated whether a spinal cord action of isoflurane affected cortical activity as determined by the electroencephalogram desynchronization that occurs after electrical stimulation of the midbrain reticular formation (MRF). Six goats were anesthetized with isoflurane, and neck dissections were performed to permit differential isoflurane delivery to the head and torso. The electroencephalogram was recorded before, during, and after focal electrical stimulation (0.05, 0.1, 0.2, 0.3, and 0.4 mA) in the MRF; in each animal, the brain isoflurane was maintained constant ( approximately 1%). When the torso isoflurane was 0.3% +/- 0.1%, the spectral edge frequency after MRF electrical stimulation (15.3 +/- 1.7 Hz, averaged across all stimulus currents) was more than the spectral edge frequency when the torso isoflurane was 1.2% +/- 0.2% (12.9 +/- 1.0 Hz, averaged across all stimulus currents; P < 0.05). Bispectral index values were similarly affected: 60 +/- 6 when torso isoflurane was low versus 53 +/- 7 at high torso isoflurane (P < 0.05). These results suggest that a spinal depressant action of isoflurane on ascending somatosensory transmission can modulate reticulo-thalamocortical arousal mechanisms, hence possibly reducing anesthetic requirements for unconsciousness and amnesia. IMPLICATIONS: Isoflurane action in the spinal cord indirectly reduces the cortical activity associated with electrical stimulation of the reticular formation, an effect that might contribute to anesthetic-induced amnesia and unconsciousness.

Anesthetics, Inhalation↗
PubMed1996

[Waking mechanisms: multiple networks in the mesencephalic reticular formation].

The hypothesis of a unique waking system located in the mesencephalic reticular formation is no longer tenable. Cortical and behavioral waking depends upon a complicated network of different systems which interact with each other with different neurotransmitters. The hierarchy of the internal structure of this network is not yet known. However, the inhibition of some strategic crossroads in this network is sufficient to suppress wake and induce sleep.

Acetylcholine↗
PubMed1996

Hypoglossal premotor neurons in the rostral medullary parvocellular reticular formation participate in cortically-induced rhythmical tongue movements.

Premotor neurons projecting to the hypoglossal (XII) nucleus and participating in cortically-induced rhythmical tongue movements were defined by extracellular recording in the cat. Two thirds (37/57) of antidromically identified XII premotor neurons sampled in the rostral medullary parvocellular reticular formation showed changes in their firing pattern during cortically-induced rhythmical activity of XII motoneurons. Fifteen of the 37 neurons showed a firing in phase with rhythmical activity of either the medial or lateral branch of the XII nerve (phasic-type). The remaining 22 neurons showed an increase in discharge with no apparent correlation with cortically-induced rhythmical activity of the XII nerve (non-phasic-type). Among the phasic- and non-phasic-type neurons, 30 neurons received inputs from the cortical masticatory area, and 14 neurons received further excitatory inputs from the inferior alveolar nerve. By systematic mapping of the stimulation sites effective for antidromic activation, four phasic-type neurons were confirmed to project to either tongue-protruding or -retracting XII motoneuron pools in accordance with their burst firing, suggesting that the phasic-type premotor neurons contribute to excitation of XII motoneurons during cortically-induced rhythmical activity. It is concluded that there are the XII premotor neurons driving cortically-induced rhythmical activity of XII motoneurons in the rostral medullary parvocellular reticular formation.

Animals↗
PubMed1989

Distribution of corticospinal neurons with collaterals to the lower brain stem reticular formation in monkey (Macaca fascicularis).

An earlier retrograde double-labeling study in cat showed that up to 30% of the corticospinal neurons in the medial and anterior parts of the precruciate motor area represent branching neurons which project to both the spinal cord and the reticular formation of the lower brain stem. These neurons were found to be concentrated in the rostral portion of the motor cortex, from where axial and proximal limb movements can be elicited. In the present study the findings in the macaque monkey are reported. The fluorescent retrograde tracer DY was injected unilaterally in the spinal cord at C2 and the fluorescent tracer FB was injected ipsilaterally in the medial tegmentum of the medulla oblongata. In the contralateral hemisphere large numbers of single DY-labeled corticospinal neurons and single FB-labeled corticobulbar neurons were present. A substantial number of DY-FB double-labeled corticospinal neurons were also found, which must represent branching neurons projecting to both the spinal cord and the bulbar reticular formation. These neurons were present in: 1. The anterior portion of the "cingulate corticospinal area" in the lower bank of the cingulate sulcus; 2. The supplementary motor area (SMA); 3. The rostral part of precentral corticospinal area; 4. The upper portion of the precentral face representation area; 5. The caudal bank of the inferior limb of the arcuate sulcus; 6. The posterior part of the insula. In these areas 10% to 30% of the labeled neurons were double-labeled. The functional implications of the presence of branching corticospinal neurons in these areas is discussed.

Animals↗
PubMed1979

[Neuronal activity specific to paradoxical sleep in the bulbar reticular formation in the unrestrained cat].

Single units were recorded in the bulbar reticular formation (BRF) of unrestrained, freely behaving Cats. In the ventromedial part of the BRF (n. reticularis magnocellularis, Mc) corresponding to the "bulbar inhibitory center", we have found a cluster of cells showing tonic activation highly selective to paradoxical sleep (PS). Furthermore, we have confirmed the presence of the same type of cells in the dorsomedial part of the BRF which corresponds to the medial part of the n. reticularis parvocellularis (Pc). The functional significance of these two groups of cells is discussed in terms of the postural atonia and the atonia of jaw closer muscles observed during PS.

Animals↗
PubMed1994

REM-enhancing effects of the adrenergic antagonist idazoxan infused into the medial pontine reticular formation of the freely moving cat.

Adrenergic input to the medial pontine reticular formation (mPRF) has been postulated to play an important role in behavioral state control. Previous work has shown that direct microinjections of the alpha 2 agonist clonidine and of norepinephrine into the mPRF suppress the REM phase of sleep. Here, we report that the alpha 2 antagonist idazoxan (IZ) enhances REM-like sleep states in the cat when microinfused into the rostral part of the mPRF at sites where carbachol produced a marked increase in REM. Significant increases in the absolute number of min in REM (70%) were observed over the entire 5 h of recordings and an especially robust increase occurred in the first hour (1000%). Other effects of IZ included increased REM duration and decreased latency to REM onset. These results represent the most marked REM-enhancing effects thus far reported for any antagonist at any brain site.

Adrenergic alpha-Antagonists↗
PubMedDate not supplied

Neuronal activity in the midbrain reticular formation related to behavioral habituation and sensitization.

Single units of the midbrain reticular formation (MRF) were recorded in the active rat (N = 10) during the presentation of repetitive trains of clicks or flashes. The movement and orienting behavior elicited by the stimuli, measured by direct observation and in terms of electrical disturbances in the recording cable, showed habituation in 14 cases, sensitization in six cases, and no decrement in nine cases. Of the 18 MRF units recorded during at least one of these behavioral conditions, seven were classed as congruent, i.e., they showed activity that paralleled the behavioral response. The majority of MRF units were behaviorally incongruent; in the most frequently observed case, their activity failed to change reliably when behavior habituated. Although the activity of congruent units generally showed moderate correlations with behavior that followed stimulation, disassociations between the two responses were commonly found. While the data are consistent with a role for the MRF in behavioral habituation and sensitization, they provide little evidence that the region is closely linked to the systems in direct control of behavior.

Acoustic Stimulation↗
PubMed1995

The striatal dopaminergic catalepsy mechanism is not necessary for the expression of pontine catalepsy produced by carbachol injections into the pontine reticular formation.

We have found previously that microinjections of carbachol into the pontine reticular formation (PRF) of rats induce an intense cataleptic state which is similar behaviorally with the catalepsy induced by systemic administration of neuroleptic drugs. In the experiments described in the present article we studied the possibility that the pontine carbachol catalepsy is generated via the intermediary of the dopaminergic cataleptogenic mechanism in the striatum. To this purpose we produced kainic acid lesions in the striatum and in the output stations of the striatal cataleptogenic mechanism-substantia nigra reticulata and the VM thalamic nucleus. Catalepsy was tested after systemic haloperidol (2 mg/kg) and pontine microinjections of carbachol (5 micrograms/1 microliter) before and after the kainic lesions. The cataleptogenic effect of carbachol injected in the pons was not attenuated by any of the three types of lesions. On the contrary, the cataleptogenic effect of haloperidol was greatly attenuated by the same lesions. These results suggest that the pontine catalepsy produced by microinjections of carbachol in PRF is generated independently of the dopaminergic cataleptogenic mechanism in basal ganglia.

Animals↗
PubMedDate not supplied

[Rearrangement of the spatial synchronization of the stratified activity of the cortex during the orienting response and upon stimulation of the nuclei of the brain stem reticular formation and mammillary bodies].

In experiments on alert rabbits it was shown with the help of correlational-spectral method that the rearrangement in the spatial organization of the activity of the first and the fifth layers in the visual and motor cortical zones during orienting reflex and high-frequency stimulation of reticular formation nuclei (NRP and NRT) is of the same type. The synchroneity in the activity of motor zone layers and the fifth layers of different areas increases in parallel. At the same time in the spectra of layer activity high-coherence theta-rhythm increases simultaneously. The data obtained permit to assume that specific rearrangement in the synchroneity of biopotentials of the studied layers during orientation reflex is due to influences of the reticular formation. The effect of mammillary bodies stimulation proved to be less effective.

Animals↗
PubMed1983

Reticular formation of the lower brainstem. A common system for cardiorespiratory and somatomotor functions: discharge patterns of neighboring neurons influenced by cardiovascular and respiratory afferents.

Experiments were done in dogs with chloralose-urethane anesthesia. Long-lasting extracellular recordings were made from the medial parts of the reticular formation of the lower brainstem for up to 250 min. The study is based on reactions of 103 neurons. The activities of 2 or 3 neighbouring neurons recorded under identical conditions with one electrode or of neurons recorded with two electrodes at the same time could be changed regularly and synchronously by experimental changes of hemodynamic or ventilatory parameters. Action potentials were separated by amplitude discrimination. Rhythmic pulsatile modulations were proved to be present in 78% of all neurons by post-event-time histograms triggered by the R-wave of the ECG. In the 96 neurons tested 86% changed their activity when arterial pressure was raised by inflating a balloon in the abdominal aorta (79% decreased and 7% increased their activity). In post-event-time histograms triggered by the start of inspiration, 83% of the neurons showed modulations of their activity with respiratory rhythm. Experimental lung inflation decreased the activity in 75% of the tested neurons, while experimental lung deflation activated 47% of the tested neurons. Stimulation of arterial chemoreceptors activated 77% of the tested neurons. It was thus demonstrated that receptors in the cardiovascular and respiratory systems exert an influence on nearly all neurons from which recordings were made in that part of the reticular formation. Arterial baroreceptors and lung stretch receptors revealed a generalized depressing effect on the neuronal activity while chemoreceptors exert a generalized augmenting effect. At different times of recording these neurons did not always react to the same extent to comparable stimulations of afferents.

Action Potentials↗