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At least 919 records · Page 51Linked to original sources
PubMed1989

Brainstem auditory evoked potentials: correlation between CT midbrain-pontine lesion sites and abolition of wave V or the IV-V complex.

Correlations between CT lesion sites and selective abolition of BAEP wave V or the IV-V complex were made in 16 patients who had discrete midbrain-pontine hemorrhages or tumors. Waves IV and V were consistently abolished by lesions involving the dorsolateral tegmentum of the midbrain-pontine junction area and the upper pons. The abolition of these waves was ipsilateral to the side of the monaural stimulation. Wave V or the IV-V complex was not affected by lesions involving the inferior colliculus, the central pons or the area dorsolateral to the aqueduct. It is concluded that an intact dorsolateral area of the upper pons is a prerequisite for waves IV and V to occur.

Adolescent↗
PubMed1990

Human M1-, M2- and M3-muscarinic cholinergic receptors: binding characteristics of agonists and antagonists.

The muscarinic acetylcholine receptors were identified in membrane preparations from human tissues by the specific binding of 1-[benzilic-4,4'-3H] quinuclidinyl benzilate. Saturation binding isotherms of this radioligand yielded a total amount of receptors of 435 +/- 208, 159 +/- 65 and 913 +/- 89 fmol/mg protein, respectively, in the hippocampus, pons and submandibular gland. Non linear least squares analysis of competition binding studies with the antagonists pirenzepine and AF-DX 116 indicates that the majority of receptors are of the M1-type in the hippocampus (83%, high affinity for pirenzepine, intermediate affinity for AF-DX 116), the M2-type in the pons (low affinity for pirenzepine and high affinity for AF-DX 116), and the M3-type in the submandibular gland (low affinity for pirenzepine and AF-DX 116). Competition binding parameters of the agonists carbachol, arecoline, oxotremorine, pilocarpine and MCN-A-343 were compared for M1, M2 and M3 receptors in the human hippocampus, pons and submandibular gland. GTP caused a shift to the right and a steepening of the shallow agonist competition curves in the 3 tissues but did not affect the initially steep ones. This effect is explained by a GTP-mediated conversion of high- to low-agonist affinity sites. The extent of the nucleotide shift was much greater for M2 receptors as compared with M1 and M3 receptors. The GTP effect was impaired by the sulphydryl reagent N-ethylmaleimide, probably due to alkylation of GTP-binding proteins. Moreover, the reagent provoked also an increase of the agonist affinity for the uncoupled muscarinic receptors. For all agonists, this increase was more pronounced for the M2 receptors than for the M1 and M3 receptors. These findings suggest structural differences between the agonist binding sites of M1 and M3 receptors versus the M2 receptors.

Binding, Competitive↗
PubMed1988

Changes of monoamine and TRH contents in naloxone induced inhibited development of rat cerebrum and cerebellum.

We have studied effects of an opioid antagonist, naloxone (NLX) on rat brain development. Newborn rats were given daily subcutaneous injection of 1 or 50 mg/kg NLX from birth until weaning (day 21). The 28 day-old rats were examined their brain development. Both doses of NLX reduced the cerebral and cerebellar weights of rats but the body weight loss was significant only in the higher dose (50 mg). However, there were neither morphological changes in the central nervous system nor movement disorders such as abnormal gait and involuntary movements in naloxone treated rats (NLX-rats). We found that serotonin content was decreased significantly in the cerebral cortex and medulla while it was significantly increased in the pons and striatum of NLX-rats. Noradrenaline was decreased significantly in the medulla while it was increased in the pons of the NLX-rats. In contrast, the concentrations of these monoamines did not show any changes in cerebellum and hippocampus of NLX-rats. On the other hand, thyrotropin-releasing hormone (TRH) was significantly decreased in cerebellum and hippocampus of NLX-rats, while it did not show any changes in cerebral cortex, medulla and pons of NLX-rats. These observations suggest that the neurotransmitters influencing the brain development, which are modulated by endogenous opioid systems, may play an important role in the development of rat brain; monoaminergic neurons play a significant role in the development of the cerebrum while TRH containing neurons may be involved in that of the cerebellum.

Animals↗
PubMed1981

Pontile axonal projections of medullary respiratory neurons.

Our purpose was to determine if any medullary respiratory neurons have axonal projections to the rostral pons. In decerebrate, vagotomized, paralyzed and ventilated cats, we monitored efferent phrenic nerve activity and activities of single respiratory and non-respiratory neurons in the regions of the dorsal (DRN) and ventral (VRN) medullary respiratory nuclei. Neurons were classified as bulbospinal, vagal or bulbopontile if stimulation of the spinal cord, vagus nerve or pons elicited antidromic action potentials. If no such action potentials were elicited, the neurons were designated as 'not antidromically activated'. Approximately ten percent of respiratory neurons in both the DRN and VRN were bulbopontile. The great majority of these exhibited tonic or phasic phase-spanning patterns of activity. Effective stimulation loci in pons extended from the area of the trigeminal motor nuclei to the Kolliker-Fuse and parabrachial nuclei. At these same loci, antidromic action potentials were also elicited for some non-respiratory medullary neurons. The possible role of bulbopontile respiratory neurons in the control of automatic ventilatory activity is discussed.

Action Potentials↗
PubMed1982

Effects of ketamine and Althesin Anesthesia on baroreceptor--heart rate reflex and hemodynamics of intact and pontine rabbits.

The changes in baroreceptor-heart rate reflex properties and in hemodynamics produced by light ketamine anesthesia were studied in one group of rabbits before and after infracollicular decerebration and those produced by althesin anesthesia in another group. Ketamine produced marked depression of baroreceptor reflex-mediated vagal effects on heart rate which was of similar magnitude in intact and pontine decerebrate rabbits; this indicates that its action was largely at or below the pons. Althesin produced much less vagal depression than ketamine in the intact rabbit but in pontine rabbits the depression was greatly enhanced. The smaller vagal depression in the intact rabbit appears to be due to a facilitatory effect through a suprapontine pathway by Althesin which partially masks its depressant effect below the pons. In the intact rabbit ketamine produced a greater rise in blood pressure than Althesin anesthesia for 1 h; the greater pressor response was due to a transient rise in total peripheral resistance (TPR) and a sustained rise in cardiac output. The difference in the blood pressure responses was mainly due to differences in action of the two anesthetics at or below the pons and only the transient rise in TPR during ketamine anesthesia was mediated through a suprapontine pathway.

Alfaxalone Alfadolone Mixture↗
PubMed1993

Neurochemical differentiation of human bulbospinal monoaminergic neurons during the first trimester.

The neurochemical differentiation of bulbospinal noradrenergic and serotonergic neurons has been followed in first trimester human fetuses. Analysis of microdissected CNS regions revealed detectable levels of noradrenaline (NA) and serotonin (5-HT) in pons, medulla oblongata and throughout the spinal cord from 5-6 weeks of gestation. In all regions there was a pronounced increase in tissue levels of the monoamines, especially from 8-9 weeks on. 5-HT levels were lower than NA levels except for pons, where the opposite was true. With increasing fetal age, the results seemed less consistent because of considerable interindividual variations. Using immunohistochemical localization of tyrosine hydroxylase (TH), a marker for noradrenergic neurons, immature cell bodies were seen in the brain stem at the earliest stage studied, that is at 4 weeks of gestation. Several TH and 5-HT-immunoreactive (IR) cell groups were found in pons and medulla oblongata at 5 weeks. Significant structural differentiation of TH- and 5-HT-IR cell bodies was seen during the first trimester. Immunoreactive fibers began to appear at 5 weeks in the cervical spinal cord. At 6 weeks both types of fibers could be found in the white matter throughout the entire spinal cord while fibers in gray matter appeared at 9 weeks. The number of TH-IR fibers was considerably larger than the number of 5-HT-IR fibers. This is the first time the biochemical development of human bulbospinal monoaminergic neurons during the first trimester has been described. Continued investigations of the ontogenetic growth and differentiation of these human bulbospinal monoaminergic neurons will gain necessary insight into the genetically determined capacity for plasticity, potentially possible to activate later in life in response to spinal cord injury. Further, intraspinal transplantation of CNS tissue relevant to the severed spinal cord would by necessity entail selection of embryonic cell populations. Using such therapeutic strategies, detailed knowledge of the inherent capacities of the donor tissues will be crucial.

Cell Differentiation↗
PubMedDate not supplied

Short latency somatosensory evoked potentials recorded around the human upper brain-stem.

We analyzed the intracranial spatiotemporal distributions of the N18 component of short latency median nerve somatosensory evoked potentials (SSEPs) in 3 patients with epilepsy. In these patients, depth electrodes were implanted bilaterally into the frontal and temporal lobes, with targets including the amygdala and hippocampus; the latter two targets are close to the upper pons and midbrain. In this study N18 was divided into the initial negative peak (N18a) and the following prolonged negativity (N18b). Mapping around the upper pons and midbrain showed that: (1) the amplitude of the first negativity, which coincided with scalp N18a, was larger contralateral to the side of stimulation, but showed no polarity change around the upper brain-stem; and (2) the second negativity, which was similar to scalp N18b, did show an amplitude difference or a polarity change. This wave appeared to reflect a positive-negative dipole directed in a dorso-ventral as well as dorso-lateral direction from the midbrain, where positivity arises from the dorsum of the midbrain, contralateral to the side of the stimulation. Recordings from depth electrode derivations oriented in a caudo-rostral direction suggest that N18a and N18b may in part reflect neural activity originating from the upper pons to midbrain region which projects to the rostral subcortical white matter of the frontal lobe as stationary peaks.

Adult↗
PubMed1987

Loss of pirenzepine regional selectivity following solubilization and partial purification of the putative M1 and M2 muscarinic receptor subtypes.

Pirenzepine inhibition of [3H]N-methylscopolamine ([3H]NMS) binding was studied in membranous, digitonin-solubilized, and partially purified muscarinic receptors from bovine cortex, an area of the brain rich in the putative M1 muscarinic receptor subtype, and from pons-medulla, an area rich in the putative M2 subtype. In accord with previous work, we found that pirenzepine bound to membranous receptors from cortex with an IC50 that was over one order of magnitude lower than to receptors from pons-medulla. After digitonin solubilization, however, this regional selectivity was significantly reduced. In receptors from pons-medulla, the IC50 for pirenzepine inhibition of [3H]NMS was reduced from 2.1 +/- 0.7 X 10(-6) M in membrane-bound receptors, to 4.3 +/- 0.3 X 10(-7) M after solubilization, whereas in receptors from cortex, the IC50 remained unchanged after solubilization. The solubilized receptors from both brain areas maintained their binding characteristics after partial purification over an ABT-Sepharose affinity column and a hydroxylapetite column. These findings raise the possibility that the different pirenzepine binding characteristics used to define M1 and M2 receptor subtypes are not inherent in the receptor protein itself, but may be due to coupling factors such as effector proteins, phospholipids or cytoskeletal proteins which could be associated with the membranous receptor and become dissociated from the receptor after solubilization.

Animals↗
PubMed1987

Immunocytochemical localization of dopamine-beta-hydroxylase in neurons of the human brain stem.

The distribution of catecholaminergic cells in the human pons and medulla was illustrated by immunocytochemistry using a polyclonal antibody directed against the catecholamine synthetic enzyme, dopamine-beta-hydroxylase. The antibody specifically recognizes dopamine-beta-hydroxylase in putative adrenergic and noradrenergic neurons. The adrenergic and noradrenergic neurons are found in the brain stem from caudal levels of the medulla through the caudalmost levels of the midbrain. Large numbers of dopamine-beta-hydroxylase-positive cells were observed in cell groups of the medulla. Additionally, dopamine-beta-hydroxylase-positive cells were concentrated in the nucleus locus coeruleus and the nucleus subcoeruleus in the pons. These studies confirm that immunocytochemical localization of dopamine-beta-hydroxylase can be used to identify noradrenergic and adrenergic neurons and their terminal varicosities in the pons and medulla in routine autopsy material. These studies have also illustrated that the distribution of dopamine-beta-hydroxylase in the adult human brain is comparable to the distribution in other species.

Adult↗
PubMed1983

A supratrigeminal region implicated in the classically conditioned nictitating membrane response.

The dorsolateral pontine brain stem was investigated as a possible locus of neural elements mediating the classically conditioned nictitating membrane (NM) response in rabbit. Recording and brain stimulation were employed for this purpose. Low-impedance tungsten monopolar microelectrodes were chronically implanted into the pontine brain stem. Multiple-unit recording during classical conditioning revealed a conditioned increase in multiple-unit activity (MUA) which developed and extinguished concurrently with the acquisition and extinction of the behavioral conditioned response. Pseudoconditioning and conditioned inhibition controls indicated that the increase in MUA was an associative learning phenomenon. Histology indicated that electrode tips recording the CR-associated electrical activity were located mostly adjacent or dorsal to the motor trigeminal nucleus. Periocular shock pulses elicited short latency evoked responses throughout most of the dorsolateral pons, suggesting that information concerning the unconditioned stimulus is relayed to this region. Furthermore, electrical stimulation of this region produced a robust ipsilateral nictitating membrane response in a number of cases, suggesting that neural elements of the dorsolateral pons project to the motoneurons that produce membrane extension. A consideration of several criteria based on these experiments implicates a supratrigeminal zone [22] as containing the neural elements of dorsolateral pons most intimately associated with the conditioned NM response. Other interpretations, concerning fibers of passage through this region and

Abducens Nerve↗
PubMed2004

Pontine GABAergic pathways: role and plasticity in the hypoxic ventilatory response.

The hypoxic ventilatory response (HVR) was compared before and after uni- and bi-lateral injections of bicuculline, a GABA(A) receptor antagonist, into the ventrolateral (vl) pons and before and after conditioning animals to chronic sustained hypoxia (CSH). The HVR was assessed by recording phrenic nerve activity (PNA) during and after brief exposures to hypoxia (8% O(2) and 92% N(2) for 45s). Inspiratory (T(I)) and expiratory (T(E)) durations were averaged before hypoxia, at the peak breathing frequency during hypoxia, before the end of hypoxia, immediately after hypoxia, and 60s after hypoxia. Blocking GABA(A) receptors in the vl pons prolonged T(E) during, but not after hypoxia. After CSH induced by 14 days in a hypobaric chamber (0.5atm), the HVR was attenuated compared to that in the naive animals. This plasticity of HVR was associated with selective induction of alpha6 and delta GABA(A) receptor subunit mRNAs specifically in the pons compared to the medulla. These physiological and molecular results illustrate the importance of pontine GABAergic pathways in shaping the response to hypoxia.

Action Potentials↗
PubMed2004

Pontine influences on breathing: an overview.

Historical and contemporary views of the functional organization of the lateral pontine regions influencing breathing are reviewed. In vertebrates, the rhombencephalon generates a breathing rhythm and detailed motor pattern that persist throughout life. Key to this process is an essentially continuous column of neurons extending from the spino-medullary border through the ventrolateral medulla, continuing through the ventral pons and arcing into the dorsolateral medulla. Comparative neuroanatomy and physiology indicate this is a richly interconnected network divided into serial, functionally distinct compartments. Serial compartmentalization of pontomedullary structures related to breathing also reflects the developmental segmentation of the rhombencephalon. However, with migration of cell groups such as the facial nucleus from the pons to the medulla during ontogeny, the boundaries of the adult pons are sometimes difficult to precisely define. Accordingly, a working definition of rostral and caudal pontine boundaries for adult mammals is depicted.

Animals↗
PubMed2002

Fos expression in non-catecholaminergic neurons in medullary and pontine nuclei after volume depletion induced by polyethylene glycol.

Fos immunocytochemistry was combined with immunolabeling for dopamine-beta-hydroxylase (DBH) to examine neuronal activation in the medulla and pons after administration of polyethelene glycol (PEG), which produces volume depletion without altering arterial blood pressure. Increased Fos immunoreactivity was observed in the area postrema, nucleus of the solitary tract, rostral ventrolateral medulla, lateral parabrachial nucleus, and the dorsomedial pons at the level of the locus coeruleus. Fos immunolabeling in the caudal nucleus of the solitary tract, rostral ventrolateral medulla, and the dorsomedial pons occurred primarily in neurons that did not contain DBH. Thus, PEG activates non-catecholaminergic neurons in medullary and pontine areas associated with cardiovascular and body fluid regulation.

Animals↗
PubMed1997

Brain corticotropin-releasing factor immunoreactivity and receptors in five inbred rat strains: relationship to forced swimming behaviour.

In the present work we studied the relationship between behaviour in the forced swimming test (FST), a test that presumably measures depressive-like behaviour in rodents, and central corticotropin-releasing factor (CRF) concentration and binding in five strains of rats. The strains were: Brown-Norway (BN), Fisher (FIS) 344, Lewis (LEW), spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). The FST data corresponding to the pretest showed significant inter-strain differences in both struggling and immobility: BN and WKY rats displayed lower levels of struggling and longer periods of immobility, LEW and SHR rats showed intermediate levels, and FIS rats were the most active. The results of the pretest were roughly similar to those observed in the test, the activity of WKY being extremely low. The CRF binding revealed significant inter-strain differences in prefrontal cortex and hippocampus, but not in cerebellum, pons-medulla or hypothalamus: in the prefrontal cortex, BN and FIS rats showed greater CRF binding than LEW, SHR and WKY rats; in the hippocampus BN rats showed higher levels of CRF binding than the other strains. The study of CRF content in various brain areas revealed inter-strain differences in prefrontal cortex and pons-medulla, but not in parietal-temporal cortex or in hypothalamus (CRF concentrations in the hippocampus were not detectable): CRF content in the prefrontal cortex was higher in BN than in the other strains, although the differences with FIS were not statistically significant; in the pons-medulla, FIS and LEW showed significantly higher CRF content than the other strains. From the present results it appears that BN and WKY rats were more prone to adopt passive strategies in the FST, but they did not show higher brain CRF immunoreactivity or down-regulation of CRF receptors. Hence, although there were inter-strains differences in all variables studied, no evidence for a relationship between the FST behaviour and central CRF activity was found.

Animals↗
PubMed1997

Modification of the binding of [3H]MK-801 to brain regions and spinal cord of rats treated chronically with U-50,488H, a kappa-opioid receptor agonist.

Male Sprague-Dawley rats were rendered tolerant to U-50,488H by twice-daily injections of the drug (25 mg/kg, i.p.) for 4 days. In tolerant rats, the binding of [3H]MK-801 was increased in pons and medulla and corpus striatum but decreased in midbrain and hippocampus and was due to changes in Bmax values. In U-50,488H-abstinent rats, the binding of [3H]MK-801 was increased in pons and medulla and hippocampus, and decreased in midbrain and amygdala. In hippocampus, the Bmax of [3H]MK-801 was increased but the Kd was decreased whereas in amygdala and pons and medulla, the changes were due to alterations in the Bmax values. Previous studies have shown that NMDA receptor antagonists block the tolerance to the analgesic action of U-50,488H in rodents. The present studies demonstrate differential changes in the NMDA receptors of brain regions of U-50,488H-tolerant and -abstinent rats.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed2000

Amylin compared with calcitonin: competitive binding studies in rat brain and antinociceptive activity.

Binding studies for rat amylin (AMY) and salmon calcitonin (sCT) were performed on rat membranes prepared from pons and medulla oblongata of rats. The aim was to see whether specific binding sites for AMY and/or for sCT present in these areas could be relevant to some of the biological activities of the two peptides. Binding sites specific for [125I]AMY are present in the pons-medulla of rat brain as AMY, but not sCT, was able to displace radiolabeled AMY binding with an IC50 = 3.7+/-0.5x10(-10) M. In contrast, binding of [125I]sCT was displaced by both sCT and AMY, although with different potencies, the IC50 for sCT being 1+/-0.1x10(-11) M, and for AMY, 1.8+/-0.08x10(-7) M. The functional significance of the presence of these binding sites was evaluated in two different nociceptive tests, hot-plate and tail-flick. In the tail-flick test neither AMY (5-10 microg/rat, i.c.v.) nor sCT (10 microg/rat i.c.v.) showed antinociceptive activity, whereas in the hot-plate test AMY (10 microg/rat, i.c.v.) significantly increased the response latencies as did sCT (250 ng/rat, i.c.v.). These results demonstrated that a 40-fold greater dose of AMY is necessary to produce a comparable antinociceptive effect to that exerted by sCT. These findings are in accordance with the low affinity of AMY for sCT binding sites in rat pons-medulla. It is therefore suggested that the central inhibitory activity of AMY on pain perception involves interaction with sCT receptors whereas the selective AMY binding sites subserve other (as yet unknown) functions.

Amyloid↗
PubMed2003

Magnetic resonance imaging demonstrates differential atrophy of pontine base and tegmentum in Machado-Joseph disease.

The pons is one of the brain areas demonstrating selective degeneration in Machado-Joseph disease (MJD), which is caused by the expansion of a polyglutamine stretch in the protein called ataxin-3. Although the resultant pontine atrophy is readily recognized by magnetic resonance imaging (MRI), the features and natural process of atrophy are not fully understood. To characterize them, we analyzed the midsagittal images of the pons obtained by MRI. We found a difference in atrophy between the pontine base and tegmentum. The reduced size of the pontine tegmentum was prominent early after the onset of clinical symptoms. No overlap was seen in the range of the area of pontine tegmentum between MJD and controls. The quotient of atrophy of the pontine tegmentum divided by age correlated well with the CAG repeat number. In contrast, the area of the pontine base correlated negatively with disease duration. Particularly, the size of the pontine base remained in the range of controls for a relatively long time after the onset of symptoms. These results suggest that the atrophic process is not uniform in the pons in MJD and that the different patterns of atrophy may be derived from the differential vulnerability in pontine structures.

Adolescent↗
PubMed1986

Participation of central norepinephrine in the development of two-kidney, one clip Goldblatt hypertension.

Two series of experiments were conducted to ascertain whether the central catecholamines would participate in the elevation of blood pressure in two-kidney, one clip (2K-1C) Goldblatt hypertensive rats. The effect of 6-hydroxydopamine (6-OHDA) injected intraventricularly (250 micrograms/kg.) before the induction of hypertension (acute phase) or after the establishment of hypertension (chronic phase) was examined in 2K-1C rats and sham rats. The evidence has been presented: 1) that the hypothalamic norepinephrine content of 2K-1C rats in acute phase is 50 per cent lower (p less than 0.001) than that of sham rats, but norepinephrine content in the pons is similar in these animals, 2) that the content of dopamine in hypothalamus or pons is similar in 2K-1C rats and normotensive age-matched sham rats in acute phase, 3) that the content of these monoamines either in hypothalamus or pons in 2K-1C rats in chronic phase is almost identical with that in sham rats, 4) that administration of 6-OHDA markedly reduced the development of hypertension in 2K-1C rats in the acute phase, but did not affect their sustained hypertension in the chronic phase. These findings suggest that hypothalamic norepinephrine participates in the development of hypertension in 2K-1C rats in the acute phase but is not connected with the maintenance of their established hypertension in the chronic phase.

Animals↗