Strychnine blockade of the non-reciprocal inhibition of trigeminal motoneurons induced by stimulation of the parvocellular reticular formation

1. Single-unit activity was recorded from neurons in the bulbar parvocellular reticular formation (PCRF) dorsal and dorsolateral to the gigantocellular reticular nucleus near its caudal boundary, and the roles of these reticular neurons in induction of rhythmical activity of trigeminal motoneurons by repetitive stimulation of the cerebral cortex (the cortical masticatory area, CMA) were studied in the paralyzed guinea pig anesthetized with urethan or with ketamine and chlorpromazine. 2. One hundred nine PCRF neurons were activated antidromically by microstimulation in either the masseter (MA) or anterior digastric (AD) motoneuron pool in the ipsilateral trigeminal motor nucleus, and orthodromically by stimulation in the contralateral CMA. Repetitive CMA stimulation induced rhythmical burst activity in these PCRF neurons in association with the rhythmical field potential in the contralateral AD motoneuron pool induced by the same CMA stimulation. The burst was synchronous with the rhythmical AD field potential in 81 neurons, 44 and 37 of which responded antidromically to stimulation in the MA and AD motoneuron pools, respectively. The remaining 28 neurons antidromically responded to stimulation in the MA motoneuron pool, and their burst corresponded in time with the period between successive AD field potentials. 3. Spike-triggered averaging of the intracellular potentials of MA and AD motoneurons (MNs) by simultaneously recorded spontaneous spikes of the PCRF neurons, which showed rhythmical burst responses during the jaw-opening phase to repetitive CMA stimulation, revealed a monosynaptic inhibitory postsynaptic potential in MA.MNs in 12 of 34 tested pairs and a monosynaptic excitatory postsynaptic potential (EPSP) in AD.MNs in 14 of 26 tested pairs. An EPSP was also found in MA.MNs after a monosynaptic latency from triggering spikes in 11 of 37 tested PCRF neurons that showed burst activity during the jaw-closing phase. 4. We conclude that both excitatory and inhibitory premotor neurons projecting to MA.MNs as well as excitatory premotor neurons projecting to AD.MNs are located in the PCRF, and that these premotor neurons relay the output of the central rhythm generator for rhythmical jaw movements in the medial bulbar reticular formation to trigeminal motoneurons, and thus participate in induction of rhythmical activities of trigeminal motoneurons by repetitive CMA stimulation.

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TRIGEMINAL PROJECTIONS IN THE RETICULAR FORMATION OF THE PONS IN THE CAT

Canadian Journal of Biochemistry and Physiology ◽

10.1139/y62-002 ◽

1962 ◽

Vol 40 (1) ◽

pp. 7-12

Author(s):

J. M. Langlois ◽

Guy Lamarche

Keyword(s):

Reticular Formation ◽

Trigeminal Nerve ◽

Unit Activity ◽

Functional Organization ◽

Pontine Reticular Formation ◽

Recording Unit ◽

Spatial Convergence ◽

The Face ◽

High Degree ◽

Stimulation Of

The projections of the trigeminal nerve in the pontine reticular formation of the cat have been investigated by recording unit activity, after physiological stimulation of the face, in 30 "encéphales isolés" preparations. No somatotopical arrangement was found but a high degree of spatial convergence onto pontine reticular units exists and a certain degree of functional organization was observed.

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Intracellular analysis of trigeminal motoneuron rhythmical activity during stimulation of pontomedullary reticular formation in anesthetized guinea pig

Journal of Neurophysiology ◽

10.1152/jn.1989.62.6.1225 ◽

1989 ◽

Vol 62 (6) ◽

pp. 1225-1236 ◽

Cited By ~ 15

Author(s):

S. M. Gurahian ◽

S. H. Chandler ◽

L. J. Goldberg

Keyword(s):

Reticular Formation ◽

Short Duration ◽

Field Potential ◽

Membrane Potentials ◽

Repetitive Stimulation ◽

Jaw Movements ◽

Postsynaptic Potentials ◽

Duration Stimulus ◽

Long Duration ◽

Stimulation Of

1. The effects of repetitive stimulation of the nucleus pontis caudalis and nucleus gigantocellularis (PnC-Gi) of the reticular formation on jaw opener and closer motoneurons were examined. The PnC-Gi was stimulated at 75 Hz at current intensities less than 90 microA. 2. Rhythmically occurring, long-duration, depolarizing membrane potentials in jaw opener motoneurons [excitatory masticatory drive potential (E-MDP)] and long-duration hyperpolarizing membrane potentials [inhibitory masticatory drive potentials (I-MDP)] in jaw closer motoneurons were evoked by 40-Hz repetitive masticatory cortex stimulation. These potentials were completely suppressed by PnC-Gi stimulation. PnC-Gi stimulation also suppressed the short-duration, stimulus-locked depolarizations [excitatory postsynaptic potentials (EPSPs)] in jaw opener motoneurons and short-duration, stimulus-locked hyperpolarizations [inhibitory postsynaptic potentials (IPSPs)] in jaw closer motoneurons, evoked by the same repetitive cortical stimulation. 3. Short pulse train (3 pulses; 500 Hz) stimulation of the masticatory area of the cortex in the absence of rhythmical jaw movements activated the short-latency paucisynaptic corticotrigeminal pathways and evoked short-duration EPSPs and IPSPs in jaw opener and closer motoneurons, respectively. The same PnC-Gi stimulation that completely suppressed rhythmical MDPs, and stimulus-locked PSPs evoked by repetitive stimulation to the masticatory area of the cortex, produced an average reduction in PSP amplitude of 22 and 17% in jaw closer and opener motoneurons, respectively. 4. PnC-Gi stimulation produced minimal effects on the amplitude of the antidromic digastric field potential or on the intracellularly recorded antidromic digastric action potential. Moreover, PnC-Gi stimulation had little effect on jaw opener or jaw closer motoneuron membrane resting potentials in the absence of rhythmical jaw movements (RJMs). PnC-Gi stimulation produced variable effects on conductance pulses elicited in jaw opener and closer motoneurons in the absence of RJMs. 5. These results indicate that the powerful suppression of cortically evoked MDPs in opener and closer motoneurons during PnC-Gi stimulation is most likely not a result of postsynaptic inhibition of trigeminal motoneurons. It is proposed that this suppression is a result of suppression of activity in neurons responsible for masticatory rhythm generation.

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

Journal of Neurosurgery ◽

10.3171/jns.1987.66.4.0548 ◽

1987 ◽

Vol 66 (4) ◽

pp. 548-554 ◽

Cited By ~ 8

Author(s):

Seigo Nagao ◽

Tsukasa Nishiura ◽

Hideyuki Kuyama ◽

Masakazu Suga ◽

Takenobu Murota

Keyword(s):

Intracranial Pressure ◽

Reticular Formation ◽

Cerebral Blood Volume ◽

Systemic Arterial Pressure ◽

Brain Swelling ◽

Dorsomedial Nucleus ◽

Medullary Reticular Formation ◽

Content Type ◽

Fine Print ◽

Stimulation Of

✓ 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.

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Convergence of heterotopic nociceptive information onto neurons of caudal medullary reticular formation in monkey (Macaca fascicularis)

Journal of Neurophysiology ◽

10.1152/jn.1990.63.5.1118 ◽

1990 ◽

Vol 63 (5) ◽

pp. 1118-1127 ◽

Cited By ~ 44

Author(s):

L. Villanueva ◽

K. D. Cliffer ◽

L. S. Sorkin ◽

D. Le Bars ◽

W. D. Willis

Keyword(s):

Electrical Stimulation ◽

Reticular Formation ◽

Mechanical Stimulation ◽

Background Activity ◽

The Body ◽

Thermal Stimulation ◽

Medullary Reticular Formation ◽

Nociceptive Information ◽

Noxious Mechanical Stimulation ◽

Stimulation Of

1. Recordings were made in anesthetized monkeys from neurons in the medullary reticular formation (MRF) caudal to the obex. Responses of 19 MRF neurons to mechanical, thermal, and/or electrical stimulation were examined. MRF neurons exhibited convergence of nociceptive cutaneous inputs from widespread areas of the body and face. 2. MRF neurons exhibited low levels of background activity. Background activity increased after periods of intense cutaneous mechanical or thermal stimulation. Nearly all MRF neurons tested failed to respond to heterosensory stimuli (flashes, whistle sounds), and none responded to joint movements. 3. MRF neurons were excited by and encoded the intensity of noxious mechanical stimulation. Responses to stimuli on contralateral limbs were greater than those to stimuli on ipsilateral limbs. Responses were greater to stimuli on the forelimbs than to stimuli on the hindlimbs. 4. MRF neurons responded to noxious thermal stimulation (51 degrees C) of widespread areas of the body. Mean responses from stimulation at different locations were generally parallel to those for noxious mechanical stimulation. Responses increased with intensity of noxious thermal stimulation (45-50 degrees C). 5. MRF neurons responded with one or two peaks of activation to percutaneous electrical stimulation applied to the limbs, the face, or the tail. The differences in latency of responses to stimulating two locations along the tail suggested that activity was elicited by activation of peripheral fibers with a mean conduction velocity in the A delta range. Stimulation of the contralateral hindlimb elicited greater responses, with lower thresholds and shorter latencies, than did stimulation of the ipsilateral hindlimb. 6. Electrophysiological properties of monkey MRF neurons resembled those of neurons in the medullary subnucleus reticularis dorsalis (SRD) in the rat. Neurons in the caudal medullary reticular formation could play a role in processing nociceptive information. Convergence of nociceptive cutaneous input from widespread areas of the body suggests that MRF neurons may contribute to autonomic, affective, attentional, and/or sensory-motor processes related to pain.

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Properties and Interconnections of Trigeminal Interneurons of the Lateral Pontine Reticular Formation in the Rat

Journal of Neurophysiology ◽

10.1152/jn.2001.86.5.2583 ◽

2001 ◽

Vol 86 (5) ◽

pp. 2583-2596 ◽

Cited By ~ 48

Author(s):

M.-J. Bourque ◽

A. Kolta

Keyword(s):

Electrical Stimulation ◽

Reticular Formation ◽

Motor Pattern ◽

High Frequency Stimulation ◽

Motor Nucleus ◽

Trigeminal Motor Nucleus ◽

Postsynaptic Potentials ◽

Frequency Stimulation ◽

Stimulation Of

Numerous evidence suggests that interneurons located in the lateral tegmentum at the level of the trigeminal motor nucleus contribute importantly to the circuitry involved in mastication. However, the question of whether these neurons participate actively to genesis of the rhythmic motor pattern or simply relay it to trigeminal motoneurons remains open. To answer this question, intracellular recordings were performed in an in vitro slice preparation comprising interneurons of the peritrigeminal area (PeriV) surrounding the trigeminal motor nucleus (NVmt) and the parvocellular reticular formation ventral and caudal to it (PCRt). Intracellular and extracellular injections of anterograde tracers were also used to examine the local connections established by these neurons. In 97% of recordings, electrical stimulation of adjacent areas evoked a postsynaptic potential (PSP). These PSPs were primarily excitatory, but inhibitory and biphasic responses were also induced. Most occurred at latencies longer than those required for monosynaptic transmission and were considered to involve oligosynaptic pathways. Both the anatomical and physiological findings show that all divisions of PeriV and PCRt are extensively interconnected. Most responses followed high-frequency stimulation (50 Hz) and showed little variability in latency indicating that the network reliably distributes inputs across all areas. In all neurons but one, excitatory postsynaptic potentials (EPSPs) or inhibitory postsynaptic potentials (IPSPs) were also elicited by stimulation of NVmt, suggesting the existence of excitatory and inhibitory interneurons within the motor nucleus. In a number of cases, these PSPs were reproduced by local injection of glutamate in lieu of the electrical stimulation. All EPSPs induced by stimulation of PeriV, PCRt, or NVmt were sensitive to ionotropic glutamate receptor antagonists 6-cyano-7-dinitroquinoxaline and d,l-2-amino-5-phosphonovaleric acid, while IPSPs were blocked by bicuculline and strychnine, antagonists of GABAA and glycine receptors. Examination of PeriV and PCRt intrinsic properties indicate that they form a fairly uniform network. Three types of neurons were identified on the basis of their firing adaptation properties. These types were not associated with particular regions. Only 5% of all neurons showed bursting behavior. Our results do not support the hypothesis that neurons of PeriV and PCRt participate actively to rhythm generation, but suggest instead that they are driven by rhythmical synaptic inputs. The organization of the network allows for rapid distribution of this rhythmic input across premotoneuron groups.

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Early postnatal development of GABAergic presynaptic inhibition of Ia proprioceptive afferent connections in mouse spinal cord

Journal of Neurophysiology ◽

10.1152/jn.00783.2012 ◽

2013 ◽

Vol 109 (8) ◽

pp. 2118-2128 ◽

Cited By ~ 9

Author(s):

Patrick M. Sonner ◽

David R. Ladle

Keyword(s):

Spinal Cord ◽

Postnatal Development ◽

Presynaptic Inhibition ◽

Dorsal Root ◽

Reciprocal Inhibition ◽

Afferent Feedback ◽

Early Postnatal Development ◽

Ia Afferent ◽

Ia Afferents ◽

Stimulation Of

Sensory feedback is critical for normal locomotion and adaptation to external perturbations during movement. Feedback provided by group Ia afferents influences motor output both directly through monosynaptic connections and indirectly through spinal interneuronal circuits. For example, the circuit responsible for reciprocal inhibition, which acts to prevent co-contraction of antagonist flexor and extensor muscles, is driven by Ia afferent feedback. Additionally, circuits mediating presynaptic inhibition can limit Ia afferent synaptic transmission onto central neuronal targets in a task-specific manner. These circuits can also be activated by stimulation of proprioceptive afferents. Rodent locomotion rapidly matures during postnatal development; therefore, we assayed the functional status of reciprocal and presynaptic inhibitory circuits of mice at birth and compared responses with observations made after 1 wk of postnatal development. Using extracellular physiological techniques from isolated and hemisected spinal cord preparations, we demonstrate that Ia afferent-evoked reciprocal inhibition is as effective at blocking antagonist motor neuron activation at birth as at 1 wk postnatally. In contrast, at birth conditioning stimulation of muscle nerve afferents failed to evoke presynaptic inhibition sufficient to block functional transmission at synapses between Ia afferents and motor neurons, even though dorsal root potentials could be evoked by stimulating the neighboring dorsal root. Presynaptic inhibition at this synapse was readily observed, however, at the end of the first postnatal week. These results indicate Ia afferent feedback from the periphery to central spinal circuits is only weakly gated at birth, which may provide enhanced sensitivity to peripheral feedback during early postnatal experiences.

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