Processing of vestibular and other inputs by the caudal ventrolateral medullary reticular formation

1996 ◽  
Vol 271 (4) ◽  
pp. R1070-R1077 ◽  
Author(s):  
B. C. Steinbacher ◽  
B. J. Yates
Keyword(s):  
Reticular Formation ◽  
Ventrolateral Medulla ◽  
Indirect Pathway ◽  
Medullary Reticular Formation ◽  
Baroreceptor Reflexes ◽  
Somatosympathetic Responses ◽  
Caudal Medulla ◽  
Sciatic Nerve Stimulation ◽  
Alpha Chloralose ◽  
Vestibulosympathetic Reflexes

Lesions of the lateral medullary reticular formation caudal to the obex abolish vestibulosympathetic and somatosympathetic responses; this area also contains neurons that mediate baroreceptor reflexes. Recordings were made from neurons in the caudal medullary reticular formation of cats that were decerebrate or anesthetized using alpha-chloralose-urethan to determine whether common neurons responded to electrical stimulation of vestibular and hindlimb afferents and had cardiac-related (i.e., baroreceptor) inputs. Many neurons in the ventrolateral portion of the caudal reticular formation received labyrinthine inputs, and they were interspersed with neurons that received baroreceptor signals. However, virtually none of the units received convergent baroreceptor and vestibular inputs, suggesting that separate pathways from the caudal ventrolateral medulla mediate baroreceptor and vestibulosympathetic reflexes. Furthermore, the neurons that received labyrinthine signals could not be antidromically activated from electrodes inserted into the rostral ventrolateral medulla, which is known to mediate vestibulosympathetic responses; thus an indirect pathway must convey vestibular inputs from the caudal to rostral medullary reticular formation. Over 75% of both neurons with baroreceptor inputs and cells with vestibular signals responded to sciatic nerve stimulation, suggesting that more than one pathway from the caudal medulla may mediate somatosympathetic responses.

Convergence of sympathetic, vagal, and other sensory inputs onto neurons in feline ventrolateral medulla

1991 ◽  
Vol 260 (6) ◽  
pp. H1918-H1928 ◽  
Author(s):  
R. W. Blair
Keyword(s):  
Blood Pressure ◽  
Reticular Formation ◽  
Sensory Input ◽  
Vagal Stimulation ◽  
Stellate Ganglion ◽  
Ventrolateral Medulla ◽  
Multiple Sources ◽  
Pressure Sensitive ◽  
Alpha Chloralose ◽  
Stimulation Of

Responses of 80 neurons in rostral and caudal ventrolateral medulla to multiple sources of sensory input were assessed in cats anesthetized with alpha-chloralose. Sixty-one of eighty-one neurons (76%) were excited by stimulation of the stellate ganglion, and one neuron exhibited inhibition followed by excitation. In response to vagal stimulation, 12% of the neurons were excited and 29% inhibited. Vagal stimulation reduced the responses of 13 of 39 (33%) neurons to sympathetic stimulation. Overall, one-third of the neurons responded to both sympathetic and vagal stimulation. There was no difference in proportion of responsive neurons in rostral versus caudal ventrolateral reticular formation. Cells were also tested for auditory, visual, and natural somatic stimuli. Ten percent of the neurons responded to all five stimuli, and another 25% responded to four stimuli. Twelve percent of neurons were unresponsive to any stimulus. Twenty cells were tested for responses to changes in blood pressure elicited with phenylephrine and nitroglycerin. Seven neurons were inhibited by increases or excited by decreases in pressure, four had the opposite responses, and nine were unresponsive. In general, blood pressure-sensitive cells exhibited comparable convergence of other inputs as the overall cell population. However, three times as many pressure-insensitive neurons received vagal input as did pressure sensitive neurons. In conclusion, neurons in the ventrolateral medulla, including the vasopressor and vasodepressor regions, receive and integrate convergent input from multiple sensory origins. Since the regions of the reticular formation studied are functionally heterogeneous, the precise functions of these neurons are not known.

Pressor responses from electrical or glutamate stimulations of the dorsal or ventrolateral medulla

1988 ◽  
Vol 255 (5) ◽  
pp. R709-R717 ◽  
Author(s):  
C. Y. Chai ◽  
R. H. Lin ◽  
A. M. Lin ◽  
C. M. Pan ◽  
E. H. Lee ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Pressor Response ◽  
Monosodium Glutamate ◽  
Pressure Rise ◽  
Ventrolateral Medulla ◽  
Induced Response ◽  
Pressor Responses ◽  
Dorsal Portion ◽  
Caudal Medulla ◽  
Alpha Chloralose

In rats, rabbits, and cats anesthetized with alpha-chloralose and urethan, responses of the pressor areas of the dorsal portion (DM) and ventrolateral portion (VLM) of medulla and pons were compared. Electrical stimulation (monopolar square-wave pulses) on monosodium glutamate solution (Glu, 100-200 nl, 1 M) was delivered through an electrode-needle tubing connected to a Hamilton syringe for semimicroinjection. In all three of these species, pressor responses were elicited from both DM and VLM by either Glu or electrical stimulation. The most active parts of DM were found in the dorsomedial reticular formation of the rostral medulla to mid-medulla. In the pons and caudal medulla, the Glu-induced response was mild, although the electrically induced response was marked. Application of kainic acid (KA) to either DM or VLM produced an initial pressor response but was followed by a reduction of the pressure rise on subsequent electrical stimulation. Glu, unlike electrical stimulation, excites neural perikarya, not fibers of passage. KA initially excites the neural perikarya before causing damage that spares axons. These results thus suggest that both DM and VLM contain neural perikarya that mediate pressor effects.

Gigantocellular vasodepressor area is tonically active and distinct from caudal ventrolateral vasodepressor area

1997 ◽  
Vol 272 (3) ◽  
pp. R731-R742 ◽  
Author(s):  
S. A. Aicher ◽  
D. J. Reis
Keyword(s):  
Spinal Cord ◽  
Reticular Formation ◽  
Kynurenic Acid ◽  
Sympathetic Nerve Activity ◽  
Raphe Nuclei ◽  
Ventrolateral Medulla ◽  
Medullary Reticular Formation ◽  
Nerve Activity ◽  
System 2 ◽  
Raphé Nuclei

The gigantocellular depressor area (GiDA) is a functionally defined subdivision of the medullary gigantocellular reticular formation where vasodepressor responses are evoked by glutamate microinjections (Aicher, S. A., D. J. Reis, D. A. Ruggiero, and T. A. Milner. Neuroscience 60: 761-779, 1994). The present experiments sought to determine whether the GiDA 1) tonically inhibits the sympathetic nervous system; 2) is necessary for baroreflex function; and 3) is functionally distinct from adjacent vasodepressor regions in the medullary reticular formation, including the midline raphe nuclei and the caudal ventrolateral medulla (CVL). Excitotoxic lesions of the GiDA abolished the baroreflex and significantly increased sympathetic nerve activity in anesthetized rats. Equivalent injections into the midline raphe nuclei elevated sympathetic activity but did not alter baroreflex responses. Therefore, the GiDA is functionally distinct from the raphe nuclei, although both contain tonically active sympathoinhibitory neurons. Because the effects of GiDA lesions were identical to those seen after lesions of the CVL, further studies were required to demonstrate that the GiDA and CVL are functionally and anatomically distinct. First, intramedullary injections of kynurenic acid produced hypertension and blocked the baroreflex when placed in the CVL, but not when placed in the GiDA. Second, muscimol inactivation of the RVL blocked the hypertension produced by excitotoxic lesions of the CVL, but failed to block the hypertension produced by similar lesions of the GiDA. Third, CVL neurons project to the RVL but not the spinal cord, whereas GiDA neurons project to the spinal cord but not the RVL. These studies show that the CVL and GiDA are both tonically sympathoinhibitory regions, but they are distinct with regard to their functional connectivity with other autonomic regions.

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

1987 ◽  
Vol 66 (4) ◽  
pp. 548-554 ◽  
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.

Nucleus tractus solitarius and control of blood pressure in chronic sinoaortic denervated rats

1992 ◽  
Vol 263 (2) ◽  
pp. R258-R266 ◽  
Author(s):  
A. M. Schreihofer ◽  
A. F. Sved
Keyword(s):  
Blood Pressure ◽  
Plasma Levels ◽  
Nucleus Tractus Solitarius ◽  
Inhibitory Influence ◽  
Baroreceptor Reflexes ◽  
Alpha Chloralose ◽  
And Control ◽  
Bilateral Destruction ◽  
Conscious Control

To determine the role of the nucleus tractus solitarius (NTS) in the tonic maintenance of arterial pressure (AP) following chronic baroreceptor denervation, the present study examined the effect of inhibition of the NTS on AP in chronic sinoaortic denervated (SAD) and control rats. One to two weeks after complete SAD (no residual arterial baroreceptor reflexes) mean AP was not significantly different from that of control rats. Bilateral microinjections of muscimol and lidocaine into the NTS markedly increased AP in alpha-chloralose-anesthetized control rats. However, microinjections of these neuroinhibitory drugs had no effect on AP in SAD rats. Similarly, 1 h after bilateral destruction of the NTS conscious control rats were hypertensive, while AP in SAD rats was not changed. Plasma levels of vasopressin (VP), which were also elevated in control rats 1 h after NTS lesions, were not significantly altered in SAD rats. These results demonstrate that inhibition of the NTS has no effect on AP or plasma levels of VP in chronic SAD rats. This suggests neither the NTS nor afferents to the NTS supply a tonic inhibitory influence on AP after chronic baroreceptor denervation.

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

1990 ◽  
Vol 63 (5) ◽  
pp. 1118-1127 ◽  
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.

scholarly journals Calcium-induced calcium release activates spontaneous miniature outward currents in newt medullary reticular formation neurons

2018 ◽  
Vol 120 (6) ◽  
pp. 3140-3154 ◽  
Author(s):  
Daniel B. Yaeger ◽  
Emma J. Coddington
Keyword(s):  
Action Potential ◽  
Reticular Formation ◽  
Calcium Release ◽  
Motor Behavior ◽  
Brain Slices ◽  
Medullary Reticular Formation ◽  
Outward Currents ◽  
Decay Times ◽  
Action Potential Threshold ◽  
Potential Threshold

Neurons in the medullary reticular formation are involved in the control of postural and locomotor behaviors in all vertebrates. Reticulospinal neurons in this brain region provide one of the major descending projections to the spinal cord. Although neurons in the newt medullary reticular formation have been extensively studied using in vivo extracellular recordings, little is known of their intrinsic biophysical properties or of the underlying circuitry of this region. Using whole cell patch-clamp recordings in brain slices containing the rostromedial reticular formation from adult male newts, we observed spontaneous miniature outward currents (SMOCs) in ~2/3 of neurons. Although SMOCs superficially resembled inhibitory postsynaptic currents (IPSCs), they had slower risetimes and decay times than spontaneous IPSCs. SMOCs required intracellular Ca2+ release from ryanodine receptors and were also dependent on the influx of extracellular Ca2+. SMOCs were unaffected by apamin but were partially blocked by iberiotoxin and charybdotoxin, indicating that SMOCs were mediated by big-conductance Ca2+-activated K+ channels. Application of the sarco/endoplasmic Ca2+ ATPase inhibitor cyclopiazonic acid blocked the generation of SMOCs and also increased neural excitability. Neurons with SMOCs had significantly broader action potentials, slower membrane time constants, and higher input resistance than neurons without SMOCs. Thus, SMOCs may serve as a mechanism to regulate action potential threshold in a majority of neurons within the newt medullary reticular formation. NEW & NOTEWORTHY The medullary reticular formation exerts a powerful influence on sensorimotor integration and subsequent motor behavior, yet little is known about the neurons involved. In this study, we identify a transient potassium current that regulates action potential threshold in a majority of medullary reticular neurons.

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