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PubMed2004

Effects of age and sex on volumes of the thalamus, pons, and cortex.

Volumes of thalamus, pons, cortical gray matter, and white matter were derived from MR brain images of healthy men and women spanning the adult age range in order to delineate patterns of aging and to compare age and sex effects in thalamus and pons with such effects in cortical gray and white matter volumes. Men had larger intracranial volume (ICV) than women, but ICV did not correlate with age in either sex. Thalamic, pontine, and cortical white matter volumes did not differ between men and women once ICV differences were taken into account, but men had more cortical gray matter than women even after accounting for ICV. Volumes of pons and thalamus were associated, independent of ICV, in women but not in men. Thalamic volume declined linearly with age at a similar rate in both men and women, whereas cortical gray matter volume declined more steeply with age in men than women. Both pontine and cortical white matter volumes remained stable across the age span in both men and women.

Adult↗
PubMed2002

Central pathways in the pons and midbrain involved in cardiac sympathoexcitatory reflexes in cats.

Activation of cardiac sympathetic afferents elicits pain and excitatory cardiovascular reflexes including acute hypertension and tachyarrhythmias. Our previous studies have shown that specific regions in the medulla, such as the nucleus of solitary tract and ventrolateral medulla, are involved in central regulation of cardiac sympathoexcitatory reflexes. However, the contributions of supramedullary nuclei to these reflexes have not been characterized. In the present study, we located activated neurons in the pons and midbrain induced by inputs from cardiac sympathetic afferents by detecting their c-Fos immunoreactivity. In anesthetized cats with bilateral carotid denervation and cervical vagotomy, epicardial application of bradykinin (1-10 microg, in 0.1 ml; n=7) was performed on the anterior surface of the left ventricle six times, every 20 min. Repetitive application of bradykinin caused consistent excitatory cardiovascular reflexes characterized by increases in blood pressure and heart rate. No responses were evoked by the vehicle for bradykinin (0.9% saline, n=7). Compared to control cats, c-Fos immunoreactive cells were significantly increased (P<0.05) in the rostral pons, caudal and intermediate midbrain in the bradykinin-treated cats. The specific areas activated include the parabrachial nucleus, Kölliker-Fuse nucleus, locus coeruleus, dorsal nucleus of raphe, and dorsal, lateral and ventrolateral periaqueductal gray. From these results we suggest that cardiovascular-related regions in the pons and midbrain form part of a long loop in central integration of cardiac sympathoexcitatory reflexes.

Administration, Topical↗
PubMed2004

Severe abnormalities of the pons in two infants with goldenhar syndrome.

We describe 2 cases of Goldenhar syndrome with severe abnormalities of the pons. The first case is a 10-month-old Caucasian female infant. At birth the girl showed polydactyly, labiopalatoschisis, right ear agenesis, left eye coloboma and vertebral anomalies. She also had marked hypotonia, severely reduced movements and respiratory and feeding abnormalities. She required gastrostomy at 5 months and tracheostomy at 7 months. Brain MRI scans showed moderate cerebellar hypoplasia and severe abnormalities of the pons with a congenital cleft. The child died at age 12 months. Case 2 is a Caucasian boy. Clinical signs and presentation were similar to case 1. The child also had severely reduced lacrimation, sweating, with thermoregulation abnormalities. He also underwent gastrostomy at 18 months. The child is now 3 years old and is able to sit only with support. Brain MRI was similar to case 1. The association of Goldenhar syndrome and pons abnormalities in 2 subjects suggests that this is more than a mere coincidence. Further studies and characterization of the genes involved in Goldenhar syndrome are needed to establish an adequate genotype-phenotype correlation.

Abnormalities, Multiple↗
PubMed2004

Effects of hypocretin2-saporin and antidopamine-beta-hydroxylase-saporin neurotoxic lesions of the dorsolateral pons on sleep and muscle tone.

The hypocretin neurons have been implicated in regulating sleep-wake states as they are lost in patients with the sleep disorder narcolepsy. Hypocretin (HCRT) neurons are located only in the perifornical region of the posterior hypothalamus and heavily innervate pontine brainstem neurons, such as the locus coeruleus (LC), which have traditionally been implicated in promoting arousal. It is not known how the hypocretin innervation of the pons regulates sleep-wake states as pontine lesions have never been shown to increase sleep. It is likely that in previous studies specific neurons were not lesioned. Therefore, in this study, we applied saporin-based neurotoxins to the dorsolateral pons and monitored sleep in rats. Anti-dopamine-beta-hydroxylase-saporin killed the LC neurons but sleep was affected only during a two hour light-dark transition period. Application of hypocretin2-saporin killed fewer LC neurons relative to other adjacent neurons. This occurred because the LC neurons possess the hypocretin receptor 1 but the ligand hypocretin 2 binds to this receptor with less affinity relative to the hypocretin receptor 2. The hypocretin2-saporin lesioned rats compared to controls had increased sleep during the dark period and displayed increased limb movements during REM sleep. None of the lesioned rats had sleep onset REM sleep periods or cataplexy. We conclude that the hypocretin innervation to the pons functions to awaken the animal when the lights turn off (via its innervation of the LC), sustains arousal and represses sleep during the rest of the night (via a wider innervation of other pontine neurons), and modulates muscle tone.

Animals↗
PubMed1985

Genesis of rhythmic respiratory activity in pons independent of medulla.

We hypothesized that rhythmic respiratory-related activity could be generated in pons independent of medullary mechanisms. In decerebrate, cerebellectomized, vagotomized, paralyzed, and ventilated cats, we recorded efferent activities of the phrenic nerve and mylohyoid branch of the trigeminal nerve. Following transections of the brain stem at the pontomedullary junction, the phrenic and trigeminal nerves discharged with independent rhythms. Spontaneous trigeminal discharges eventually ceased but were reestablished after strychnine, doxapram, and/or protriptyline were administered. In some animals having no spontaneous trigeminal discharges after transection, these discharges appeared, with a rhythm different from the phrenic, following administration of these agents. In other cats having no transections between pons and medulla, these pharmacological agents induced trigeminal and phrenic discharges after kainic acid had been injected into the entire dorsal and ventral medullary respiratory nuclei. Phrenic and trigeminal discharges were linked, indicating survival of bulbospinal neurons or presence of pontospinal units. We conclude that rhythms, similar to respiratory rhythm, can occur by mechanisms in isolated pons. Such mechanisms are hypothesized to be within the pneumotaxic center and may underlie the neurogenesis of eupnea.

Action Potentials↗
PubMed1990

Effects on breathing of rostral pons glutamate injection during opossum development.

To determine whether pathways from the rostral pons, capable of influencing breathing, were present in immature mammals, the excitatory amino acid glutamate (sodium salt) was pressure injected in very small volumes into the rostral pons of suckling and adult opossums. The youngest animals tested were approximately 3 wk old (1.5-2.9 g). Animals were anesthetized with the thiobarbituric acid derivative, Inactin, and the electromyogram of the diaphragm was used to assess changes in breathing rhythm and ventilatory output. Glutamate concentrations of 50, 150, and 1,000 mM were injected into the rostral pons. Active sites were generally located between parabrachial and either lateral lemniscal or trigeminal nuclei. Effects of glutamate in opossums of all ages included changes in diaphragm activity and respiratory timing over several breaths. In the youngest animals, a very high incidence of apnea occurred as an initial response (17 of 20 sites) at the 1,000 mM concentration. The high incidence of apneic response in the youngest animals suggests that strong activation of rostral pontine neurons can more easily disrupt respiratory output; a physiological circumstance of such activation might include a diving response stimulated by trigeminal afferents.

Animals↗
PubMed2005

Saccade-related, long-lead burst neurons in the monkey rostral pons.

The paramedian pontine reticular formation contains the premotoneuronal cell groups that constitute the saccadic burst generator and control saccadic eye movements. Despite years of study and numerous investigations, the rostral portion of this area has received comparatively little attention, particularly the cell type known as long-lead burst neurons (LLBNs). Several hypotheses about the functional role of LLBNs in saccade generation have been proposed, although there is little information with which to assess them. To address this issue, I mapped and recorded LLBNs in the rostral pons to measure their discharge characteristics and correlate those characteristics with the metrics of the concurrent saccades. On the basis of their discharge and location, I identified three types of LLBNs in the rostral pons: excitatory (eLLBN), dorsal (dLLBN), and nucleus reticularis tegmenti pontis (nrtp) LLBNs. The eLLBNs, encountered throughout the pons, discharge for ipsilateral saccades in proportion to saccade amplitude, velocity, and duration. The dLLBNs, found at the pontomesencephalic junction, discharge maximally for ipsilateral saccades of a particular amplitude, usually <10 degrees , and are not associated with a particular anatomical nucleus. The nrtp LLBNs, previously described as vector LLBNs, discharge for saccades of a particular direction and sometimes a particular amplitude. The discharge of the eLLBNs suggests they drive motor neurons. The anatomical projections of the nrtp LLBNs suggest that their involvement in saccade production is less direct. The discharge of dLLBNs is consistent with a role in providing the "trigger" signal that initiates saccades.

Action Potentials↗
PubMed1994

Pharmacological characterization of muscarinic cholinergic receptors in cat pons and cortex. Preliminary study.

Muscarinic receptors (mAChRs) in the pontine reticular formation comprise a critical part of the REM sleep-generating system. Although the role of specific mAChR subtypes remains unclear, data from in vivo microinjection studies suggest that in the pons the M2 subtype is important for REM sleep generation. The present study tested the hypothesis that M2 antagonists would show a greater binding potency in feline pons than M1 or M3 antagonists. Competition binding assays showed 4-DAMP to be more potent than pirenzepine or AF-DX 116 in its ability to displace tritiated quinuclidinyl benzilate, and linear regression analyses indicated that 4-DAMP and pirenzepine each interacted with more than one binding site. These data demonstrate the presence of a mixture of mAChR subtypes in the feline pons, and are consistent with the view that REM sleep is mediated by more than one mAChR subtype.

Animals↗
PubMed1991

Response of plasma adrenocorticotropin to injections of L-glutamate or norepinephrine in the dorsal rostral pons of cats.

Previously, electrical stimulation of several nuclei in the dorsal rostral pons of the cat was shown to modulate the release of ACTH. However, the stimulation may have activated fibers of passage. To determine if there are specific groups of neurons within the pons that modulate plasma ACTH when stimulated with glutamate, 30 cats were prepared acutely under chloralose anesthesia. Microinjections of several agents were made at each of 2 sites in the pons of each cat. ACTH was measured by RIA. Injections of 150 mM L-glutamate (100 nl/min.2 min) elicited increases in arterial pressure that were related to the loci of injection. The responses did not decrease significantly when the rate and volume of the injection were reduced by half. Eight sites in a lateral area that extended rostrally from the parabracheal nucleus elicited a significant pressor response that was greater in duration and magnitude than a second significant pressor response that was obtained from 18 sites in a medial area that included the rostral locus coeruleus. Pressor responses did not occur when 0.1 mM norepinephrine or vehicle was substituted for L-glutamate in any area. The larger, but not the smaller, dose of L-glutamate elicited changes in plasma ACTH that were related to the loci of injection. Eight sites in a caudal area that included the ventral locus coeruleus and was within the medial pressor area elicited a significant increase in ACTH. Seven sites in an area rostral to the ventral locus coeruleus that included the rostromedial locus subcoeruleus elicited a significant decrease in plasma ACTH. ACTH responses were not observed when 0.1 mM norepinephrine or vehicle was substituted for L-glutamate in any area. In conclusion, the ventral locus coeruleus and the rostrally adjacent locus subcoeruleus contain neurons with receptors for L-glutamate that can modulate plasma ACTH and arterial pressure independently of a second pathway that includes the parabracheal region and influences arterial pressure. Because the neurons in the coeruleus are known to respond to hemodynamic input, they may participate in the hemodynamic control of ACTH release.

Adrenocorticotropic Hormone↗
PubMed1985

Stereotactic surgery for mass lesions of the midbrain and pons.

Appropriate treatment for intracranial mass lesions depends upon accurate histological diagnosis. Although both advanced generation computed tomographic and magnetic resonance scanners can detect small lesions within the brain stem, only the combination of these advanced imaging tools with stereotactic instrumentation permits safe and accurate pathological diagnosis of such lesions. We present the results of 13 operations performed on 12 patients with mass lesions of the pons and mesencephalon. A definitive diagnosis was obtained in all patients. Aspiration of necrotic tumors (3 patients), neoplastic or benign cysts (2 patients), and chronic hematomas (2 patients) resulted in immediate neurological improvement in 7 of these 12 patients. No morbidity or mortality related to surgery occurred in this series. Both the preoperative clinical and radiographic diagnoses were erroneous in 6 patients so that accurate histological diagnosis indeed altered subsequent therapy. A transfrontal approach to the midbrain and a transcerebellar approach to the lateral pons are described. The importance of accurate diagnosis, the possibility of definitive therapy in selected patients, and the encouraging benefits and safety of stereotactic surgery indicate that empiric treatment of mass lesions of the midbrain and pons is no longer justified.

Adolescent↗
PubMed1997

Acetylcholinesterase activity in the pons and medulla oblongata of rats after chronic electroconvulsive shock.

An imbalance between cholinergic and noradrenergic neurotransmission has been proposed for the etiology of affective disorders. According to this hypothesis, depression would be the result of enhanced cholinergic and reduced noradrenergic neurotransmission. Repeated electroconvulsive shock (ECS) is an effective treatment for depression; moreover, in laboratory animals it induces changes in brain noradrenergic neurotransmission similar to those obtained by chronic treatment with antidepressant drugs (down-regulation of beta-adrenergic receptors). The aim of the present study was to determine whether repeated ECS in rats changes acetylcholinesterase (Achase) activity. Achase controls the level of acetylcholine (Ach) in the synaptic cleft and its levels seem to be regulated by the interaction between Ach and its receptor. Thus, a decrease in Achase activity would suggest decreased cholinergic activity. Adult male Wistar rats received one ECS (80 mA, 0.2 s, 60 Hz) daily for 7 days. Control rats were handled in the same way without receiving the shock. Rats were sacrificed 24 h after the last ECS and membrane-bound and soluble Achase activity was assayed in homogenates obtained from the pons and medulla oblongata. A statistically significant decrease in membrane-bound Achase activity (nmol thiocholine formed min-1 mg protein-1) (control 182.6 +/- 14.8, ECS 162.2 +/- 14.2, P < 0.05) and an increase in soluble Achase activity in the medulla oblongata (control 133.6 +/- 4.2, ECS 145.8 +/- 12.3, P < 0.05) were observed. No statistical differences were observed in Achase activity in the pons. Although repeated ECS induced a decrease in membrane-bound Achase activity, the lack of changes in the pons (control Achase activity: total 231.0 +/- 34.5, membrane-bound 298.9 +/- 18.5, soluble 203.9 +/- 30.9), the region where the locus coeruleus, the main noradrenergic nucleus, is located, does not seem to favor the existence of an interaction between cholinergic and noradrenergic neurotransmission after ECS treatment.

Acetylcholinesterase↗
PubMed2002

Corpus callosum, pons, and cortical white matter in alcoholic women.

BACKGROUND: To measure the effect of alcohol abuse on white matter brain macrostructure in women with alcoholism and to determine whether observed abnormalities interact with age. METHODS: Quantitative measures of corpus callosum area, cortical white matter volume, and pons volume were derived from magnetic resonance imaging scans obtained from 34 women with DSM-III-R alcoholism (aged 28-64, mean 41 years) and 35 healthy women (aged 22-65, mean 42 years). Transverse relaxation time of the pons was also obtained. RESULTS: No significant group differences in any brain measures were observed. However, in alcoholics greater length of sobriety was associated with more cortical white matter, and higher lifetime levels of alcohol consumption were associated with smaller volumes and prolonged transverse relaxation time in the pons. CONCLUSIONS: Despite a lack of overall deficits in white matter macrostructural size in alcoholic women, certain white matter structures showed alcohol exposure vulnerability whereas others showed evidence of recovery with abstinence.

Adult↗
PubMed1991

Double-labelling data on somatostatin-like and tyrosine-hydroxylase-like immunoreactivities in chick embryo brain stem. I. Pons and mesencephalon.

With the aim of investigating some factors and mechanisms of the chicken brain development, the same thick sections of brain stems from twelve E13-to-E21-aged chick embryos were sequentially tested with a rabbit anti-Somatostatin antiserum, using a PAP-DAB technique, and with anti-tyrosine hydroxylase (-TH) monoclonal antibodies, using an indirect immuno-fluorescence technique. As regards the pons and mesencephalon, the following main results were obtained. At E21 almost the same distribution of the TH-like immunoreactivity (ir) as at E13 was observed. Neuroblasts in a central, relatively wide region of mesencephalic tegmentum and in the central portion of the pons showed TH-like ir. A co-localization of the 2 immunoreactivities was detected only at E18, within some neuroblasts of the mesencephalic and pontine regions with TH-like ir. It is possible that this transitory co-localization plays a role in the development of the pons and mesencephalon of this species.

Animals↗
PubMed1988

Respiratory activity of the pons and its influence on breathing in the guinea pig.

The localization of respiratory activity in the pons of the anaesthetized guinea pigs has been studied. The respiration related units were localized in/or close to the following anatomical structures: nucleus parabrachialis, nucleus trigemini motorius and nucleus reticularis pontis caudalis. The influence of the pontine respiratory activity on the pattern of breathing was studied by the use of a reversible pharmacological block (local anaesthetic) of these structures. The application of lignocaine to all investigated sites of the pons caused the prolongation of both respiratory phases, then an effect comparable to vagotomy. In the vagotomized animal the focal block of nucleus parabrachialis has never produced apneusis (pronounced prolongation of inspiration and very short lasting expiration). Since the removal of some pontine structures involved in the breathing control caused the depression of respiration, we concluded that the respiratory activity of the pons in the guinea pigs exerts an excitatory influence on the rhythm generating mechanism in this animal.

Action Potentials↗
PubMed1987

[Report on successful surgery of cavernous angioma in the dorsal part of the pons--usefulness of MRI in diagnosis].

A case with cavernous angioma which was located in the dorsal of the pons was cured surgically. A 16-year-old male was admitted with complaints of right motor and sensory disturbance. On neurological examination, the patient had right hemiparesis and hemiparesthesia, and right cerebellar signs. X-ray CT scan demonstrated a high density mass in the pons. Carotid and vertebral angiograms showed no abnormality. T1 and T2 weighted MRI clarified the pontine mass not as a tumor but a hematoma. Then, from the age of the patient, his clinical course, follow up X-ray CT and MRI findings, it was considered that a pontine lesion must have been an angioma with hemorrhage. Therefore, the operation was performed in an attempt to removal the hematoma and the mass of abnormal vessels in the dorsal part of the pons. Histological examination of the surgical specimen revealed abnormal vessels as a cavernous angioma. The postoperative course was uneventful.

Adolescent↗
PubMed1995

Sudden infant death syndrome: postnatal changes in the volumes of the pons, medulla and cervical spinal cord.

The brainstem and cervical spinal cord were sampled from 45 cases of sudden infant death syndrome (SIDS), from 17 control cases without neurological disease, and from three negative control cases with abnormal growth of the central nervous system (36-98 postconceptional weeks). Morphometric analyses were performed on serial Nissl sections to determine the total volumes of the pons, nucleus pontis, medulla and cervical spinal cord. Normal development was characterized by a linear increase in the volumes of these regions during the first postnatal year. Regression analysis revealed that in SIDS cases the rates of increase in the volumes of the pons and nucleus pontis were significantly greater than in controls (56% and 83%, respectively), while growth rates did not differ significantly for the medulla and cervical spinal cord. By direct comparison, there was a significant increase in the mean volumes of the pons (33%), nucleus pontis (38%) and medulla (19%) in SIDS cases when compared to controls. No evidence of excessive edema or gliosis was noted in the brainstem by light and electron microscopy to account for the increased volumes. Subtle morphological abnormalities in brainstem neurons from SIDS cases, including an increased size of Nissl bodies in the cytoplasm of large motor neurons and the presence of paranucleolar coiled bodies, were consistent with an increased synthesis and transport of ribosomal RNA, an increased synthesis of cellular proteins and neuronal hypertrophy.

Apnea↗
PubMedDate not supplied

Cerebral amyloid angiopathy and intracerebral hemorrhage with special reference to the pons.

Cerebral amyloid angiopathy accounts for approximately 10% of spontaneous intracerebral hemorrhage, typically in the cortex and subcortical white matter. Its contribution to primary pontine hemorrhage is not known. The present study was designed to determine if amyloid angiopathy occurs in the pons and whether primary pontine hemorrhages are associated with amyloid infiltration of nearby vessels. Two groups of patients were identified. Group A included 30 patients with proven CAA in whom special blocks of the pons were taken, group B consisted of 10 primary pontine hemorrhages in whom transverse blocks were available. A congo red stain and an A4 immunohistochemical technique were used. Only 1 patient from group A and none from group B had amyloid angiopathy in the pons. It is concluded that pontine angiopathy is rare and an exceptional cause of primary pontine hemorrhage.

Aged↗
PubMed1993

C-fos expression in the pons and medulla of the cat during carbachol-induced active sleep.

Microinjection of carbachol into the rostral pontine tegmentum of the cat induces a state that is comparable to naturally occurring active (REM, rapid eye movement) sleep. We sought to determine, during this pharmacologically induced behavioral state, which we refer to as active sleep-carbachol, the distribution of activated neuron within the pons and medulla using c-fos immunocytochemistry as a functional marker. Compared with control cats, which were injected with saline, active sleep-carbachol cats exhibited higher numbers of c-fos-expressing neurons in (1) the medial and portions of the lateral reticular formation of the pons and medulla, (2) nuclei in the dorsolateral rostral pons, (3) various raphe nuclei, including the dorsal, central superior, magnus, pallidus, and obscurus, (4) the medial and lateral vestibular, prepositus hypoglossi, and intercalatus nuclei, and (5) the abducens nuclei. On the other hand, the mean number of c-fos-expressing neurons found in the masseter, facial, and hypoglossal nuclei was lower in carbachol-injected than in control cats. The data indicate that c-fos expression can be employed as a marker of state-dependent neuronal activity. The specific sites in which there were greater numbers of c-fos-expressing neurons during active sleep-carbachol are discussed in relation to the state of active sleep, as well as the functional role that these sites play in generating the various physiological patterns of activity that occur during this state.

Animals↗