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PubMed1981

Mesencephalic reticular formation stimulation effects on hypothalamic neuronal activity.

The effects of mesencephalic reticular formation (RF) single pulse, 0.5 msec and 0-500 microA, stimulation on lateral preoptic-lateral hypothalamic (LPA-LH) neuronal activity were determined in anesthetized rats. In addition, the effects of LH stimulation on neural activity in the RF and periaqueductal gray (PAG) were evaluated. Recordings from 117 neurons indicate reciprocal connections between the LPA-LH and the mesencephalon. Stimulation of the RF affected 70% of the LPA-LH neurons tested. Short latency decreases in activity predominated indicating an inhibitory synaptic input from the RF to the LPA-LH. Short latency increases in discharge frequency were observed infrequently. Stimulation of the LH affected only 32% of the mesencephalic neurons tested. Short latency decreases in activity were usually observed indicating reciprocal inhibitory synaptic connections between the LPA-LH and the RF and periaqueductal gray. Antidromic responses verified these interconnections and revealed relatively slow conduction velocities of approximately 1.0 m/sec. Results are discussed in terms of the involvement of the LPA-LH and RF in sensorimotor functions, spinal motor excitability, and ingestive behavior.

Action Potentials↗

PubMed2003

Expression of pro-inflammatory cytokine and caspase genes promotes neuronal apoptosis in pontine reticular formation after spinal cord transection.

We identified apoptotic neurons in pontine reticular formation (PRF), the origin of pontine reticulospinal fibers, in adult Sprague-Dawley rats after complete spinal cord transection (SCT) at T8 level. SCT also increased the expression in PRF of tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, IL-6, caspase-1, or caspase-3 mRNA. This was followed by an augmented expression of activated caspase-3 protein, an increase in caspase-3 activity, and expression of a cleaved fragment of poly(ADP-ribose) polymerase (PARP), a proteolytic substrate of the activated caspase-3. Microinjection bilaterally into the PRF of an antiserum against TNF-alpha attenuated the expression of IL-6 mRNA and up-regulation of caspase-3 mRNA, and a caspase-3 inhibitor, DEVD-CHO, suppressed the augmentation in activated caspase-3 or cleaved PARP expression after SCT. Both treatments also reduced the number of SCT-induced apoptotic PRF neurons. We conclude that PRF neurons in adult mammalian brain may actively degrade themselves after SCT through apoptosis, via signaling processes that involve activation of proinflammatory cytokine genes and the intracellular caspase-3 pathway.

Animals↗

PubMed2003

Ultrastructural features of synapse from dorsal parvocellular reticular formation neurons to hypoglossal motoneurons of the rat.

The dorsal parvocellular reticular formation (PCRt) receives projection of the trigeminal mesencephalic nucleus neurons. It contains the dorsal group of interneurons that integrate and coordinate activity of the oral motor nuclei. Ultrastructural features of synaptic connection from the dorsal PCRt neurons to the motoneurons of the hypoglossal nucleus (XII) were examined at both the light and electron microscopic levels in rats. Biotinylated dextran amine (BDA) was initially iontophoresed into the dorsal part of PCRt unilaterally. Seven days later horseradish peroxidase (HRP) was injected into the body of the tongue. After histochemical reaction for visualization of HRP and BDA, the BDA-labeled fibers and terminals were seen distributing bilaterally in XII with ipsilateral predominance. BDA-labeled terminals were closely apposed upon HRP retrogradely labeled somata and dendrites of the XII motoneurons. A total of 1408 BDA-labeled boutons were examined ultrastructurally, which had mean size of 1.22+/-0.37 microm in diameter. Five hundred-ninety three of these boutons in both the ipsilateral (n=401) and contralateral (n=192) XII were seen to synapse on both the dendrites and somata of HRP-labeled motoneurons. The vast majorities of synapses were axodendritic (98%, 580/593), while 2% of them were axosomatic. Of the 1408 BDA-labeled boutons, 69.6% of them were S-type boutons containing small clear and spherical synaptic vesicles and 30.4% of them were PF-type boutons containing pleomorphic and flattened synaptic vesicles. Approximately 64% of synapses between BDA-labeled boutons and HRP-labeled motoneurons were asymmetric, and 33% of synapses were symmetric. No axoaxodendritic or axoaxosomatic synaptic triad was observed. The present study illustrated the anatomical pathway and synaptological characteristics of neuronal connection between the dorsal PCRt premotor neurons and the XII motoneurons. Its functional significance in coordinating activity of XII motoneurons during oral motor behaviors has been discussed.

Animals↗

PubMed1985

Enhancement of long-term potentiation in the rat dentate gyrus by post-trial stimulation of the reticular formation.

The possibility that post-trial stimulation of the mesencephalic reticular formation (m.r.f.) may modulate long-term potentiation (l.t.p.) at the perforant path to dentate granule cell synapses was studied in freely moving rats. Extracellular potentials evoked in the dentate gyrus by test pulses to the perforant path were recorded before and at various delays after a series of high-frequency stimulus trains to the perforant path (ten trains of eight pulses at 400 Hz, delivered at 5 min intervals). We have compared the magnitude and duration of l.t.p. of the population spike in this control condition with that observed when a low-intensity m.r.f. stimulation was delivered 10 s after each train to the perforant path. Post-event m.r.f. stimulation enhanced the amount of l.t.p. induced by the series of high-frequency stimulus trains and prolonged its duration for several days. The size of the population spike was unaffected by repeated m.r.f. stimulation in the absence of perforant path high-frequency stimulation, or when this failed to induce significant l.t.p. The temporal gradient of efficacy of m.r.f. stimulation was investigated. M.r.f. stimulation delivered 10 s after a single high-frequency stimulation of perforant path fibres resulted in an enhanced l.t.p. of both the population excitatory post-synaptic potential (e.p.s.p.) and population spike. L.t.p. was unaffected by m.r.f. stimulation given either before, or 120 s after perforant path high-frequency stimulation. These results show that low-intensity m.r.f. stimulation enhances lasting changes in synaptic function in the dentate gyrus when delivered during a critical period following high-frequency activation of perforant path fibres. These results are discussed in the light of our previous findings on the effects of post-event m.r.f. stimulation on memory and on the development of associative changes in hippocampal multiunit activity during conditioning. It is hypothesized that l.t.p.-like mechanisms may be involved in the stabilization of neural networks by experience and that this process might be reinforced by diffuse m.r.f. activation.

Action Potentials↗

PubMed2002

Substance P in the descending cholinergic projection to REM sleep-induction regions of the rat pontine reticular formation: anatomical and electrophysiological analyses.

Release of acetylcholine within the pontine reticular formation (PRF) from the axon terminals of mesopontine cholinergic neurons has long been hypothesized to play an important role in rapid eye movement (REM) sleep generation. As some of these cholinergic neurons are known to contain substance P (SP), we used anatomical, electrophysiological and pharmacological techniques to characterize this projection in the rat. Double immunofluorescence demonstrated that 16% of all cholinergic neurons within the mesopontine tegmentum contained SP; this percentage increased to 27% in its caudal regions. When double immunofluorescence was combined with retrograde tracing techniques, it was observed that up to 11% of all SP-containing cholinergic neurons project to the PRF. Whole-cell patch-clamp recordings from in vitro brainstem slices revealed that SP administration depolarized or evoked an inward current in a dose-dependent manner in all PRF neurons examined, and that these effects were antagonized by a SP antagonist. The amplitude of the SP-induced inward current varied with changes in the Na+ concentration, did not reverse at the calculated K+ or Cl- equilibrium potentials, and was not attenuated in the presence of tetrodotoxin, low Ca2+ concentration or caesium ions. These data suggest that activation of a tetrodotoxin-insensitive cation channel(s) permeable to Na+ is responsible for a SP-induced inward current at resting membrane potentials. The depolarizing actions of SP appeared to be primarily due to activation of the adenylate cyclase pathway, and were additive with cholinergic receptor activation even at maximal concentrations. These data indicate that SP is colocalized in a subpopulation of mesopontine tegmental cholinergic neurons projecting to REM sleep-induction regions of the PRF, and that actions of these two neuroactive substances on PRF neurons are additive. If SP is coreleased with acetylcholine, the additive actions of the two neurotransmitters might heighten the excitability of postsynaptic PRF neurons and ensure the initiation and maintenance of REM sleep.

Animals↗

PubMed1996

Responses of medullary reticular formation neurons to input from the male genitalia.

1. The medullary reticular formation (MRF) is known to be involved in the modulation of certain reproductive behaviors. Ejaculation in the male, disrupted after spinal transection, may depend on a spinal-bulbo-spinal connection. To determine whether single neurons in the MRF receive sensory input from the male genitalia, the present study was undertaken using electrophysiological techniques. 2. The MRF of 14 urethan-anesthetized mature male rats was searched for single neurons responsive to bilateral electrical stimulation of the dorsal nerve of the penis (DNP). In addition, each DNP-responsive neuron was tested for responsiveness to bilateral electrical stimulation of the pelvic nerve (PN) and to mechanical stimulation (gentle touch, pressure, pinch) of the external genitalia, anus, urethra, and skin over most regions of the body. 3. A total of 165 single neurons responsive to bilateral electrical stimulation of the DNP were isolated and characterized throughout the MRF. All neurons responded to both ipsilateral and contralateral DNP stimulation. The majority of responses were excitatory, and most neurons had no background activity. Some neurons required wind-up with bilateral electrical stimulation of the DNP to respond. 4. About half of the neurons were located in the nucleus reticularis gigantocellularis (Gi); the remainder were located in surrounding (dorsal, ventral, lateral) regions of the MRF. Variations in response properties were found among neurons located in different MRF regions. 5. Eighty-eight DNP-responsive neurons were additionally responsive to bilateral electrical stimulation of the PN. None of the responses to bilateral PN were stronger than those for bilateral DNP and many (48%) were weaker. 6. Of the 165 DNP-responsive neurons, all were responsive to pressure/pinching of the penis; 16% responded to gentle stroking of the glans. Most of these neurons were additionally responsive (bilaterally) to pinching more than one (often all) of the following areas: perineum, scrotum, anus, ears, and toes (forefoot and hindfoot). 7. In conclusion, neurons located in the MRF of male rats are involved in the processing of bilaterally convergent inputs from multiple cutaneous and visceral regions of the body, including the penis and male urogenital tract. These neurons likely exert their effects by directly and/or indirectly activating ascending pathways to rostral regions of the brain important for somatovisceral sensation and motor behavior, and descending pathways to the spinal cord for modulation of segmental sexual reflexes. Contributions are likely for a wide spectrum of sensations and reproductive behaviors.

Animals↗

PubMed1993

Axons and synapses mediating startle-like responses evoked by electrical stimulation of the reticular formation in rats: symmetric and asymmetric collision effects.

A new method for determining the locations, directions of transmission and transmission times of synapses mediating electrically evoked responses is proposed here. Electrical stimulation of pontine or medullary reticular formation with one 0.1-ms pulse evokes a short-latency startle-like response. Two pulses were delivered to single sites at various interpulse intervals and the currents required to evoke a criterion startle response were measured. The results suggest that the startle-evoking substrates have absolute refractory periods that range from 0.25-0.6 ms. When one pulse was delivered to a caudal pontine site and a second pulse was delivered to a an ipsilateral medulla site, decreases in required current were observed as interpulse interval increased from +0.4 to +0.8 ms or as interpulse interval decreased from -0.4 to -0.8 ms. These collision-like effects, being symmetric around an interpulse interval of 0, suggest that electrically evoked startle is mediated by fast axons that pass longitudinally through medulla. When one pulse was delivered to the rostral pons and a second pulse to the ipsilateral medulla, however, required currents decreased sharply as interpulse intervals increased from +0.4 to 1.0 ms and as interpulse intervals decreased from +0.2 to -0.2 ms. These asymmetric collision-like effects suggest that strong synapses in the caudal pons, transmitting from pons to medulla, mediate electrically evoked startle. The 0.3-ms asymmetry suggests that the transmission time (i.e., from presynaptic stimulus to postsynaptic action potential) averaged 0.3 ms via monosynaptic connections. The short duration of collision (0.7 ms) suggests that only one postsynaptic action potential was produced with high probability for each presynaptic action potential. From the localization of these effects and the short refractory periods, we estimate that < 60 giant cells on each side of the ventral pontine reticular formation mediate the startle reflex in the rat.

Animals↗

PubMed1983

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

Extracellular recordings were made from 103 neurons located in the medial parts of the reticular formation of the lower brainstem of chloralose-urethane anesthetized dogs. Activities of 2 or 3 neighbouring neurons under identical conditions could be recorded with one electrode. In 9 recordings it was possible to register simultaneously up to 5 neurons with two electrodes placed in both halves of the medulla. Action potentials of individual neighbouring neurons were identified by amplitude discrimination. The influences of somatosensory afferents from skin, joints and muscles on neuronal discharge patterns were tested. Responses of single neurons were characterized by multisensory afferent spectra including afferents from various parts of the body. The combinations of afferents converging onto neighbouring neurons were similar, whereas neurons in more distant parts of the medulla revealed different combinations of converging afferents. In long-lasting recordings the influence of somatosensory afferents on the discharge behaviour changed from time to time. When the discharge behaviour was mainly determined by somatosensory afferents, neighbouring neurons were shown to be organized in sub-populations. The results led to the conclusion that in this part of the reticular formation different types of functional organization of the neuronal network are possible. The type of functional organization depends on the actual preponderances of different inputs to the neurons.

Animals↗

PubMedDate not supplied

[Neuromediator sensitivity of neurons of the reticular formation and orbital cortex in hungry and satiated rabbits].

In conditions of stereotaxic fixation, noradrenaline microionophoresis and stimulation of the lateral hypothalamus acted in the same sense on impulse activity of 35 and 37% of the neurones in the reticular formation of satiated rabbits, in joint action increasing the number of cells with distribution of intervals characteristic of alimentary motivational excitation. Microionophoresis of acetylcholine to the neurones of the orbital cortex in freely behaving rabbits reshaped the impulse activity of 57% of cells in accordance with the pattern of discharge activity characteristic of alimentary motivational excitation. Such excitation, natural as well as artificially evoked, widens polychemical properties of the neurones of the reticular formation and, on the contrary, narrows polychemical properties of the nerve cells of the orbital cortex.

Acetylcholine↗

PubMedDate not supplied

[Spectral characteristics of the EEG of the visual and motor cortices in the rabbit during stimulation of the reticular formation of the brain].

Study of amplitude-frequency characteristics of dominating spectral maxima in the delta, theta and alpha-ranges of the rabbit visual and motor neocortical areas has shown that an increase of the midbrain reticular formation stimulation frequency from 60 to 1000 imp/s leads to an increase in both area of dominating rhythms frequencies in the theta and alpha-ranges, and to a decrease of the alpha-rhythm amplitude. The theta-rhythm amplitude in the visual area declines while in the motor area a slight increase is observed and then a decrease. Characteristics of the dominating frequency component in the delta-range are determined by three types of oscillations with different types of dependence on frequency of reticular formation stimulation. The most significant differences between areas are manifest in the spectrum amplitude characteristics. Qualitatively similar changes are also seen in correlation of power of spectral ranges in both areas but quantitatively they are more expressed in the motor area.

Alpha Rhythm↗

PubMed1999

Isoflurane blunts electroencephalographic and thalamic-reticular formation responses to noxious stimulation in goats.

BACKGROUND: Anesthetics, including isoflurane, depress the electroencephalogram (EEG). Little is known about the quantitative effects of isoflurane on EEG and subcortical electrical activity responses to noxious stimulation. The authors hypothesized that isoflurane would depress the results of EEG and subcortical response to noxious stimulation at concentrations less than those needed to suppress movement. Furthermore, determination of regional differences might aid in elucidation of sites of anesthetic action. METHODS: Ten goats were anesthetized with isoflurane, and minimum alveolar concentration (MAC) was determined using a noxious mechanical stimulus. Depth electrodes were inserted into the midbrain reticular formation and thalamus. Needle electrodes placed in the skull periosteum measured bifrontal and bihemispheric EEG. The noxious stimulus was applied at each of four anesthetic concentrations: 0.6, 0.9, 1.1, and 1.4 MAC. RESULTS: At an isoflurane concentration of 0.6 MAC, the noxious stimulus activated the midbrain reticular formation, thalamic, and bifrontal-hemispheric regions, as shown by decreased high-amplitude, low-frequency power. For all channels combined (mean +/- SD), total (-33+/-7%), delta (-47+/-12%), theta (-23+/-12%), and alpha (-21+/-6%) power decreased after the noxious stimulus (P < 0.001); beta power was unchanged. At 0.9 MAC, total (-35+/-5%), delta (-42+/-7%), theta (-35+/-8%), and alpha (-23+/-11%) power decreased after the noxious stimulus (P < 0.001); beta power was unchanged. At 1.1 MAC only one site, and at 1.4 MAC, no site, had decreased power after the noxious stimulus. CONCLUSIONS: Isoflurane blunted EEG and midbrain reticular formation-thalamus activation response to noxious stimulation at concentrations (1.1 MAC or greater) necessary to prevent movement that occurred after noxious stimulation. It is unknown whether this is a direct effect or an indirect effect via action in the spinal cord.

Anesthesia, Inhalation↗

PubMed1990

Microinjections of nicotine in the medial pontine reticular formation elicits REM sleep.

Microinfusion of non-specific cholinergic muscarinic-nicotinic agonists, such as carbachol, into the medial pontine reticular formation readily elicits REM sleep. It has generally been assumed that muscarinic receptors mediate the action of cholinergic agonists in triggering rapid eye movement (REM) sleep. Very little is known, however, about the role of nicotinic mechanisms in REM sleep generation. In this study, we administered nicotine and Ringer's solution into the medial pontine reticular formation of freely moving cats. Compared to control Ringer's injections, nicotine increased REM sleep and decreased wake and slow wave sleep (SWS) I percentage. Nicotine also shortened the time to REM sleep onset. These findings suggest a role of nicotinic mechanisms in REM sleep generation.

Animals↗

PubMed2001

The antinociceptive and sedative effects of carbachol and oxycodone administered into brainstem pontine reticular formation and spinal subarachnoid space in rats.

UNLABELLED: To clarify the supraspinal and spinal actions of a cholinergic agonist, carbachol, and an opioid, oxycodone, we studied their antinociceptive and behavioral effects when administered into brainstem medial pontine reticular formation (mPRF) or spinal subarachnoid space with or without pretreatment of muscarinic receptor subtype antagonist. Sprague-Dawley rats were implanted with a 24-gauge stainless steel guide cannula into the mPRF and chronically implanted with a lumbar intrathecal catheter. Antinociception was tested using tail flick latency, motor coordination was evaluated by the rotarod test, and overt sedation was assessed using a behavioral checklist. Carbachol (0.5-4.0 microg) administered into the mPRF produced significant dose- and time-dependent antinociception, sedation, and motor dysfunction. These were completely blocked by pretreatment with atropine and the M(2) muscarinic antagonist, methoctramine, and partially blocked by pretreatment with M(1) pirenzepine but not with M(3) p-fHHSID: Oxycodone administered into the mPRF did not produce such effects. Spinal carbachol and oxycodone produced antinociception without any behavioral effects; their antinociceptive effects were completely blocked by pretreatment with atropine and M(2) antagonist. These results suggest that the antinociceptive action of carbachol is mediated by muscarinic cholinergic receptor activation, especially by M(2) receptor subtype in mPRF and spinal cord, and that although oxycodone seems unlikely to affect the cholinergic transmission of mPRF, spinal oxycodone-induced analgesia is at least partly mediated via the activation of M(2) receptor subtype at the spinal cord. IMPLICATIONS: Carbachol-induced antinociception and sedation is mediated with the activation of M(2) muscarinic receptors. Oxycodone administered into brainstem medial pontine reticular formation did not cause any antinociceptive or behavioral effects, but its spinal administration produced a significant antinociception via M(2) muscarinic receptor activation

Analgesics, Non-Narcotic↗

PubMed1986

Direct projections from the reticular formation of the medulla oblongata to the anterior cingulate cortex in the mouse and the rat.

After injections of horseradish peroxidase into the anterior cingulate cortex of the mouse and the rat, labeled neurons were observed in different nuclei of the reticular formation of the rostral medulla oblongata: ventral part of the nucleus gigantocellularis, nucleus paragigantocellularis and nucleus lateralis reticularis. Other labeled neurons lay scattered outside the nuclear boundaries, often close to the ventral-most border of the medulla. The projection to the cingulate cortex is sparse, with rarely more than 3 cells per case, but constant. Injections into other cortical areas (visual, motor and somatosensory cortex) did not produce labeling in the medullary reticular formation.

Afferent Pathways↗

PubMed1995

Pontine reticular formation neurons exhibit a premature and precipitous increase in acoustic responses prior to audiogenic seizures in genetically epilepsy-prone rats.

The genetically epilepsy-prone rat (GEPR-9) exhibits elevated seizure sensitivity and audiogenic seizures (AGS). The pontine reticular formation (PRF) is implicated in the neuronal network for AGS in the GEPR-9. The present study examined PRF neuronal firing and convulsive behavior simultaneously in the GEPR-9. Chronically implanted microwire electrodes in PRF allowed single neuronal responses and behavior to be examined in freely-moving rats. PRF neurons in the GEPR-9 exhibit precipitous intensity-evoked increases at a significantly lower (approx. 15 dB SPL) intensity than normal Sprague-Dawley rats. PRF neurons in the GEPR-9 also exhibit increased auditory response latencies. At the onset of AGS (wild running) the firing rate of PRF neurons increased, and the rate of PRF firing increased dramatically as the tonic phase of the seizure began. During post-ictal depression the rate of PRF neuronal firing slowed, gradually returning to normal. This pattern of PRF periseizural neuronal firing changes differ dramatically in pattern and temporal characteristics from those previously observed in inferior colliculus (IC). The IC serves as the AGS initiation site. IC neurons show extensive firing increases prior to and during the initial wild running, silence during the tonic and post-ictal phases, and gradual recovery of responses thereafter. The changes in PRF neuronal firing pattern suggest that the PRF may play a major role in the generation of the tonic phase of AGS. The premature onset of the precipitous rise in PRF neuronal firing suggests that the influence of the IC on PRF neurons may be magnified in association with AGS susceptibility. The PRF neuronal firing increases observed in the present study coupled with previous observation of AGS blockade by PRF microinjections in the GEPR-9 further support an important role of the PRF in the propagation of AGS in the GEPR-9. The mechanisms of PRF firing elevation may also be relevant in other seizure models in which the brain-stem reticular formation is implicated.

Acoustic Stimulation↗

PubMed1993

Synaptic mechanisms acting on lumbar motoneurons during postural augmentation induced by serotonin injection into the rostral pontine reticular formation in decerebrate cats.

Intrapontine microinjections of serotonin in acutely decerebrated cats resulted in the bilateral augmentation of the postural muscle tone of the hindlimbs. Optimal injection sites were located in the dorsomedial part of the rostral pontine reticular formation corresponding to the nucleus reticularis pontis oralis (NRPo). In this study, attempts were made to elucidate the cellular basis for the serotoninergically induced augmentation of postural muscle tone by recording the electromyographic (EMG) activity of hindlimb extensor muscles, the monosynaptic reflex responses evoked by electrical stimulation of group Ia muscle afferent fibres and the membrane potentials of hindlimb alpha-motoneurons (MNs). Serotonin injections resulted not only in the augmentation of the EMG activity of gastrocnemius soleus muscles, but also in the restoration of EMG suppression, which was induced by previous injection of carbachol into the NRPo. Extensor and flexor monosynaptic reflex responses were facilitated by serotonin injections into the NRPo. Such reflex facilitation was not induced by serotonin injections into the mesencephalic or the medullary reticular formation. Intrapontine serotonin injections resulted in membrane depolarization of extensor and flexor MNs with decreases in input resistance and rheobase. Spontaneous depolarizing synaptic potentials (EPSPs) increased in both frequency and amplitude. Peak voltage of Ia monosynaptic EPSPs also increased. Serotonin injections which followed carbachol injections resulted in membrane depolarization of MNs along with an increase in the frequency of spontaneous EPSPs and a decrease in carbachol-induced inhibitory postsynaptic potentials. Following pontine carbachol injections, antidromic and orthodromic responses in MNs were suppressed. Discharges of MNs evoked by intracellular current injections were also suppressed, but were restored following serotonin injections. These results indicate that postsynaptic excitation, presynaptic facilitation and disinhibition (withdrawal of postsynaptic inhibition) simultaneously act on the hindlimb MNs during serotonin-induced postural augmentation and restoration.

Animals↗

PubMed1985

Reticular formation of the lower brainstem. A common system for cardio-respiratory and somatomotor functions. Cross-correlation analysis of discharge patterns of neighbouring neurones.

Temporal relations of discharges of 73 pairs of neurones located in the medial parts of the reticular formation of the lower brainstem were studied by cross correlation analyses in chloralose-urethane anaesthetized dogs. The action potentials of 2 or 3 neighbouring neurones were recorded with one electrode simultaneously. Uncorrelated discharges of neurones and 4 different types of correlated discharges were observed in cross correlation histograms: they were: (1) rhythmic couplings with frequencies between 2 and 5 Hz related to the same rhythm in the EEG; (2) strong, non-rhythmic couplings with short latencies up to 5 ms; (3) a combination of strong and rhythmic couplings, and (4) high-frequency oscillation couplings. Most pairs of neurones showed different types of correlation during the recordings. The different forms of correlated discharge behaviour could be related to different types of functional organization of the neuronal network in the reticular formation.

Afferent Pathways↗

PubMed1980

[Convergent properties and chemical sensitivity of neurons of the reticular formation of the midbrain of unanesthetized rabbits].

Neuronal responses of the midbrain reticular formation to light and sound stimuli as well as stimuli of negative biological modality (electric skin stimulation, stimulation of the ventromedial hypothalamus), were compared to neuronal sensitivity to microionophoretic administration of acetylcholine, noradrenaline and serotonine. The reticular neurons were shown to possess obvious interrelated convergent and chemical properties which suggests the neurochemical maintenance of integrative activity of these neurons. However, no significant correlation was revealed among neuronal responses to separate types of stimulation and their sensitivity to a certain transmitter.

Acetylcholine↗