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At least 37 records · Page 2Linked to original sources
PubMed1997

A pilot investigation into the use of vestibulometric measures in predicting neural pathways in relation to vibrotactile stimulation.

Research in the use of vibrotactile devices has focused predominantly on the vibrotactile receptor system within the skin. There is little research relating to the neural pathways and the central processing of information transmitted to the cortex as a result of vibrotactile stimulation. This pilot study that considers the use of vestibulometric measures in predicting the neural pathways. Three measures of vestibular function were undertaken: saccadic eye movement, smooth pursuit and optokinetic nystagmus. Ten normally hearing adults, with no previous history of vestibular dysfunction, were tested using an ICS computer based vestibular testing system. All subjects were tested in four situations: baseline, wearing vibrotactile device with stimulation, vibrotactile device without stimulation and repeated baseline. Five subjects demonstrated a significant change in vestibular measures, four related to measure of optokinetic nystagmus and two in relation to smooth pursuit. There is a demonstrated difference in vestibular function which supports the need for further investigation.

Adult↗
PubMed2006

Murine auditory brainstem evoked response: putative two-channel differentiation of peripheral and central neural pathways.

Standard noninvasive recordings of the auditory brainstem evoked response (ABR) from a single pair of obliquely oriented electrodes (typically midline vertex referenced to mastoid) confound inherently distinct signals propagating over peripheral and central neural pathways differing in location and spatial orientation. We describe here a technique for recording short-latency auditory evoked potentials that putatively differentiates peripheral and central neural activity in the mouse and rat. The technique involves recording from two orthogonally oriented electrode pairs using fast sample rates (100 k/s) to accurately measure differences in neural timing and waveform morphology. Electrodes oriented in a transverse plane (mastoid-to-mastoid) register an initial positive-going ABR peak (P1T) earlier than a series of peaks recorded from electrodes oriented along the midline (anterior and posterior to the inter-aural line). The absolute P1T latency is consistent with an origin in the primary auditory nerve, while the delayed midline latencies implicate activity farther along central neural pathways. Differences between these latencies (midline minus transverse) provide new and precise measures of central conduction time (CCT), which in one case is as brief as 0.10 ms. Results in wild type (WT) and knockout (KO) mice, as well as rats, show significant differences in absolute latencies as well as CCT.

Acoustic Stimulation↗
PubMed1995

Role of antral intramural neural pathways in control of gastric emptying in the pig.

1. The role of antral intramural pathways in the control of antropyloric motility and gastric emptying was evaluated in five conscious pigs equipped with chronic gastric and duodenal cannulae. Neural pathways were divided by transection and re-anastomosis of the antrum 2 cm proximal to the pylorus. Concurrent measurements of gastric emptying, transpyloric flow and antropyloric motility were performed before and 6 weeks after surgery. 2. Antral transection retarded gastric emptying, only 36% of 1000 ml saline being emptied in 30 min compared with 62% before transection. Transection did not alter the number of transpyloric flow pulses (22.0 +/- 4.0 cf. 24.4 +/- 3.2 pre-transection), but reduced (P < 0.01) the volume of flow pulses substantially (8.6 +/- 0.4 cf. 18.7 +/- 1.5 ml pre-transection). 3. Antral transection was associated with a reduction in the rate of distal antral pressure waves (P < 0.05), but no alteration in the rate of phasic low level pressurization of the entire gastric content by gastric contractions (gastric common cavity pressure waves). However, transection was associated with a significant (P < 0.05) shortening of the interval between the onset of gastric common cavity pressure waves, and the onset of lumen-occlusive pyloric pressure waves generated by the same contraction sequence (3.2 +/- 0.3 cf. 7.9 +/- 0.6 s). 4. Transection did not alter the inhibition of antral pressure waves, stimulation of localized pyloric pressure waves, and retardation of gastric emptying produced by infusion of 25% dextrose into the duodenum. 5. These studies suggest that antral intramural nerves regulate the emptying of liquids from the stomach by modulating the timing of pyloric closure in relation to phasic gastric antral and corpus contractions. 6. Distal antral intramural neural pathways do not appear to play a major role in the suppression of antral motor activity produced by duodenal glucoreceptors.

Animals↗
PubMed1994

Physiological evidence of neural pathways involved in reflexogenic penile erection in the rat.

To elucidate neural pathways responsible for the occurrence of reflexogenic erections, the response of the corpus cavernosum to electrical stimulation of the dorsal nerve of the penis (DNP) was measured in anesthetized, acutely spinalized rats. Stimulation elicited a dramatic increase in intracavernous pressure (ICP). ICP response was decreased by 70% after sectioning the pelvic nerve homolaterally to the stimulated DNP and abolished after bilateral section. ICP response was not impaired by curarization, but its latency was lengthened. Thus we physiologically evidenced a reflex loop independent from supraspinal centers between DNP and the pelvic nerve supporting penile reflexogenic erection.

Animals↗
PubMed1991

Central neural pathway mediating splanchnic osmosensation.

To determine the central neural pathway which carries splanchnic osmosensory information to vasopressin (AVP) neurons in the hypothalamus, bilateral electrolytic lesions were placed in the ascending catecholaminergic fiber bundle, the locus coeruleus (LC), the locus subcoeruleus (subLC), the lateral parabrachial nucleus (LPB), the caudal periaqueductal gray (PAG) and the median preoptic nucleus (MPO). Six and seven days later, plasma AVP levels, plasma osmolality, mean arterial pressure and heart rate were measured following gastric infusion of hypertonic (598 mosm/kg; 2 ml/4 min) or isotonic (290 mosm/kg) saline in conscious rats with indwelling tail artery catheters and nasogastric tubes. The most effective pontine lesions, which were located in the ventral locus subcoeruleus (vsubLC) approximately 1.0 mm below the LC, decreased the AVP response to hypertonic gastric infusion by 59.7% (P less than 0.05) as compared to sham-lesioned controls. In addition, unilateral vsubLC lesions dramatically reduced the catecholamine innervation of the ipsilateral paraventricular nucleus (PVN), as qualitatively determined with dopamine beta-hydroxylase immunocytochemistry, suggesting that a pathway ascending with catecholaminergic fibers was disrupted. Lesions of the MPO were also very effective, decreasing the AVP response to hypertonic saline infusion by 60.3% (P less than 0.05), suggesting that the MPO is an integral relay center in this pathway. On the other hand, LC, LPB and PAG lesions were ineffective. Systemic plasma osmolality or cardiovascular factors did not mediate the AVP response. These results demonstrate, for the first time, that splanchnic osmotic information is transmitted to the hypothalamus via pathways within the ascending catecholaminergic fiber bundles, the MPO is a relay center where peripheral and central osmotic information may be integrated, and the LC, LPB, and PAG are not part of the splanchnic osmotic pathway.

Afferent Pathways↗
PubMed1978

Central neural pathways for angiotensin-induced thirst.

Evidence is reviewed implicating the preoptic region in angiotensin-induced thirst. The most responsive area according to results obtained with behavioral, electrophysiological, and autoradiographic mapping techniques is at the caudal border of the medial preoptic region and rostral border of the anterior hypothalamus. The neural pathway from this preoptic site for angiotensin-induced thirst extends along the medial forebrain bundle through the midlateral hypothalamus to the paramedial midbrain tegmentum and to an area ventrolateral to the central gray. Lesions of this pathway in the midlateral hypothalamus and rostral midbrain significantly attenuated drinking induced by microinjections of angiotensin II into the preoptic area but did not disrupt water intake induced by microinjections of angiotensin II into the subfornical organ or cerebral ventricles. Although the efferent pathways from angiotensin-receptive sites in the subfornical organ and cerebral ventricles are unknown, it appears from these observations that the medial forebrain bundle is not involved. Lesions of the medial forebrain bundle-lateral hypothalamus also do not disrupt drinking induced by microinjections of hypertonic saline into the preoptic region although lesions placed 1 mm further lateral do. Since fat lateral hypothalamic lesions are without effect on drinking induced by centrally administered angiotensin II, this suggests that intracellular and extracellular thirst signals are subserved by separate neural pathways in the hypothalamus.

Action Potentials↗
PubMed2002

Visualizing selective neural pathways with WGA transgene: combination of neuroanatomy with gene technology.

Functional logic employed by the nervous system for information processing resides mainly in the wiring patterns among specific types of neurons. Therefore, detailed knowledge on neuronal networks is essential for understanding a wide range of brain functions. A powerful and long-awaited method for analyzing the neuronal connectivity patterns would be to deliver tracers selectively to specific types of neurons and at the same time to label transsynaptically their axonal target neurons. For this purpose, we took advantage of a unique property of plant lectin, wheat germ agglutinin (WGA), which has been used as a transsynaptic tracer in classical neuroanatomical studies. We developed a novel genetic strategy that employs WGA cDNA as a transgene, for the visualization of selective and functional neural pathways in the nervous system. In this article, I will introduce several examples of neural pathways visualized with the WGA transgene and discuss about its further refinement and applications.

Animals↗
PubMed1984

A role for neural pathways in exercise hyperpnea.

The ventilatory response to exercise induced by stimulation of the peripheral ends of severed sciatic nerves was studied in seven anesthetized dogs. In response to exercise (n = 23) there were increases in expired minute ventilation (delta VE = 4.09 l/min), arterial CO2 partial pressure (delta PaCO2 = 3.06 Torr), and carotid artery temperature (delta Tca = 0.26 degrees C). There was also a concomitant decrease in mean arterial blood pressure (delta MAP = -6.28 Torr). Since the neural pathways from the exercising limbs to the central nervous system had been eliminated by nerve section, the significant increase in PaCO2 during exercise indicates that humoral factors alone cannot produce the normal exercise response, i.e., an isocapnic hyperpnea. Therefore, neural pathways may play a fundamental role in the ventilatory response to exercise in intact animals.

Animals↗
PubMed2001

Neural pathways from the lamina terminalis influencing cardiovascular and body fluid homeostasis.

1. The lamina terminalis, a region of the brain with a high concentration of angiotensin AT1 receptors, consists of three distinct nuclei, the median preoptic nucleus, the subfornical organ and organum vasculosum of the lamina terminalis (OVLT). These latter two regions lack a blood-brain and detect changes in plasma angiotensin (Ang) II concentration and osmolality. 2. Efferent neural pathways from the lamina terminalis to the hypothalamic paraventricular and supraoptic nuclei mediate vasopressin secretion in response to plasma hypertonicity and increased circulating levels of AngII. 3. Studies using the neurotropic virus pseudorabies, which undergoes retrograde transynaptic neuronal transport following injection into peripheral sites, show that neurons in the lamina terminalis have efferent polysynaptic neural connections to the peripheral sympathetic nervous system. Some of these neurons have been shown to have polysynaptic connections to the kidney and to express AT1 receptor mRNA. We propose that circulating AngII acts at AT1 receptors in the subfornical organ and OVLT to influence the sympathetic nervous system. It is likely that the neural pathway subserving this influence involves a synapse in the hypothalamic paraventricular nucleus. 4. The lamina terminalis may exert an inhibitory osmoregulatory influence on renin secretion by the kidney. This osmoregulatory influence may be mediated by inhibition of renal sympathetic nerve activity and appears to involve a central angiotensinergic synapse. 5. The lamina terminalis exerts an osmoregulatory influence on renal sodium excretion that is independent of the renal nerves and is probably hormonally mediated.

Angiotensin II↗
PubMed1995

MR imaging in the diagnosis of intramedullary spinal cord diseases that involve specific neural pathways or vascular territories.

Prior to the advent of MR imaging, the internal architecture of the spinal cord could not be directly imaged. The solution of many technical problems (e.g., respiratory motion, cardiac and CSF pulsation, inadequate spatial resolution) has provided the opportunity for an increasingly refined analysis of intramedullary lesions. This article begins with a brief review of the results of high-resolution MR imaging studies of the cadaveric spinal cord. The article then focuses on MR imaging in the diagnosis of intramedullary diseases that involve specific neural pathways or vascular territories. Lesions are categorized as degenerative, inflammatory, traumatic, or ischemic. These diseases generally have distinctive clinical findings that reflect dysfunction of particular ascending sensory tracts or descending motor tracts. The corresponding abnormalities on MR images reflect the pathologic changes that occur in the affected neural pathways. Knowledge of the appearance of these diseases on MR images allows the formation of a narrow differential diagnosis and, in many cases, the confident exclusion of neoplasm as the cause of myelopathy.

Humans↗
PubMed1986

Neural pathways involved in intracisternal bombesin-induced inhibition of gastric secretion in rats.

Possible humoral and neural components mediating intracisternal bombesin (500 ng)-induced inhibition of gastric secretion were studied in rats. Intracisternal bombesin induced a marked rise in gastric pH from 2.0 +/- 0.5 up to 6.5 +/- 0.6 whereas gastric secretion in parabiotic saline-treated partners was not modified. Bombesin inhibited pentagastrin-stimulated gastric acid output by 88 +/- 5% in intact rats and 71 +/- 7% in vagotomized animals. Spinal cord transection at the level of the 5th or 7th cervical but not the 8th or 13th thoracic vertebrae significantly reversed the rise in pH and the decrease in acid concentration induced by bombesin and abolished the hyperglycemic effect of the peptide. These results suggest that bombesin inhibitory action on gastric secretion is not mediated through humoral factors but through neural pathways in part related to the sympathetic nervous system along the spinal cord, whereas the parasympathetic outflow from the vagus or the sacral spinal nerves does not seem to play an important role.

Animals↗
PubMed1992

Neurochemical and morphological evidence of an antinociceptive neural pathway from nucleus raphe dorsalis to nucleus accumbens in the rabbit.

Previous studies using a pharmacological approach suggested a neural pathway emanating from the periaqueductal gray (PAG) to the nucleus accumbens relevant to antinociception. This was investigated with neurochemical and histochemical methods in the present study. Push-pull perfusion and radioimmunoassay were used to measure the release of immunoreactive-(ir) enkephalin (ir-ENK) and ir-beta-endorphin (ir-beta-EP) in the nucleus accumbens after microinjection of morphine into the PAG and the nucleus raphe dorsalis (NRD) of the rabbit. Morphine administration elicited an increase in ir-ENK and ir-beta-EP in the nucleus accumbens. Horseradish peroxidase (HRP) retrograde tracing in combination with 5-hydroxytryptamine (5-HT) immunocytochemistry revealed a serotonergic projection from the NRD and ventral PAG to the nucleus accumbens in the rabbit. About 7% of the serotonin-positive cells in the NRD and ventral PAG send fibers directly to the nucleus accumbens, with an ipsilateral dominance. These results indicate the existence of a serotonergic pathway from the NRD to the N. accumbens involved in opioid analgesia.

Animals↗
PubMed2004

Dissociable neural pathways for the perception and recognition of expressive and instrumental gestures.

Previous functional imaging studies have sought to characterize the neural correlates of gesture representation. However, little is yet known about the representation of different categories of gesture. Here we contrasted the perception of hand gestures that express inner feeling states, e.g. I am angry, I do not care, with the perception of instrumental gestures intended to change the behavior of others by communicating commands, e.g. come here, look over there. We hypothesised that recognition of expressive gestures would activate a network of brain regions associated with mentalising ('theory of mind') whereas instrumental gestures would activate different neural pathways. Twelve normal volunteers underwent fMRI while they watched a series of short videos (3 s duration) of actors performing expressive and instrumental gestures. The volunteers had either to recognise the gesture or to monitor the positions of the hands. As predicted, different neural networks were activated by the observation of instrumental or expressive gestures. The perception of expressive gestures elicited activity in the anterior paracingulate cortex, the amygdala and the temporal poles bilaterally and the right superior temporal sulcus. These regions have all previously been activated during the performance of mentalising tasks. In contrast, instrumental gestures elicited activity in a left-lateralised system previously associated with language and motor imitation.

Adult↗
PubMed1985

Neural pathways mediating adrenocortical responses.

The effects of hypothalamic deafferentations and brain lesions on adrenocorticotropin (ACTH) and corticosterone (CS) responses after neural stimuli were studied in rats. It was found that the various modalities are mediated by different neural pathways. Photic and acoustic stimuli utilize a posterior input, whereas the sciatic and olfactory modalities are mediated by anterior afferents and forebrain limbic structures. The effects of limbic extrahypothalamic structures on the hypothalamus are transmitted by both anterior and posterior inputs. The medial forebrain bundle (MFB) was found to have a differential role in the mediation of ACTH and CS responses. To identify the neurotransmitters involved, rats were injected with 6-hydroxydopamine in the MFB and 5,7-dihydroxytryptamine in the raphe nuclei. The depletion of hypothalamic norepinephrine and serotonin caused inhibition of the adrenocortical responses only after photic stimulation, and only of responses to limbic stimuli in the former group. In view of the location of corticotropin-releasing factor in the paraventricular nucleus, responses to afferent stimuli were studied in this region in identified neurons projecting to the median eminence. Stimuli that increased or decreased CS secretion facilitated or inhibited cell firing, respectively, thus demonstrating a possible electrophysiological correlate of neuroendocrine regulation.

5,7-Dihydroxytryptamine↗
PubMed1981

The neural pathway involved in "efferent inhibition" of chemoreceptors in the cat carotid body.

This study was done to determine whether a pathway of efferent axons in the carotid sinus nerve is necessary for the phenomenon of "efferent inhibition" (inhibition induced in carotid body chemoreceptors by electrical stimulation of the carotid sinus nerve). Our approach was to eliminate efferent axons in the carotid sinus nerve of cats without destroying the sensory axons. This was achieved by cutting the ipsilateral glossopharyngeal and vagus nerves central to their sensory ganglia and/or by removing the nodose and superior cervical ganglia. In neurophysiological studies we found that the response of chemoreceptors in cats 10 days after surgery was the same as that in controls. chemoreceptor activity was decreased by electrical stimulation of the carotid sinus nerve and was increased by hypoxia and cyanide. In operated cats as in control animals, "efferent inhibition" was abolished by haloperidol and dihydroergotamine, drugs that block the inhibitory action of dopamine. Electron microscopic studies disclosed that the number of nerve endings in glomus cell/sheath cell complexes was not measurably different in control and experimental carotid bodies. By contrast, 10 days after the carotid sinus nerve was cut the number of nerve endings next to such ells was reduced by more than 99%. cutting the nerve roots and excising the ganglia eliminated most nerve endings on blood vessels: The number of noradrenergic-type nerve endings was reduced 99% and other types of nerve endings (presumptive cholinergic and peptidergic types) were reduced by more than 90%. Our experiments indicate that "efferent inhibition" is not abolished by operations that destroy inputs to blood vessels and to carotid boy glomus cells from (1) the nodose ganglion, (2) superior cervical ganglion, or from (3) neurons in the brain stem whose axons run in the glossopharyngeal or vagus nerves. We conclude that " efferent inhibition" may be caused by antidromic stimulation of sensory axons.

Animals↗
PubMed2003

A hypothalamic-testicular neural pathway is influenced by brain catecholamines, but not testicular blood flow.

We previously reported the existence of a descending multisynaptic, pituitary-independent, neural pathway between the hypothalamus and the testes in the male rat. Stimulation of this pathway by the intracerebroventricular (icv) injection of IL-1beta or corticotropin-releasing factor blunts the testosterone (T) response to human chorionic gonadotropin (hCG). This response is mediated at least in part by catecholamine beta-adrenergic receptor activation. The present work was performed to further investigate the role of brain catecholamines and testicular blood flow in this pathway. The icv injection of 5 microl of 200 proof ethanol (EtOH; 86 micromol) did not result in detectable levels of the drug in the general circulation and did not induce neuronal damage, but rapidly blunted hCG-induced T release while not decreasing LH levels or altering testicular blood flow. EtOH significantly up-regulated transcripts of the immediate-early gene c-fos in the paraventricular nucleus (PVN) of the hypothalamus. Lesions of the PVN blocked the inhibitory effect of IL-1beta on T, but only partially interfered with the influence of EtOH. PVN catecholamine turnover significantly increased after icv injection of IL-1beta, but not EtOH. Brain catecholamine depletion due to the neurotoxin 6-hydroxydopamine did not alter the ability of hCG to induce T release, but significantly reversed the inhibitory effect of icv EtOH or IL-1beta on this response. Collectively, these results indicate that icv-injected IL-1beta or EtOH blunts hCG-induced T secretion through a catecholamine-mediated mechanism that does not depend on either peripherally mediated effects or pituitary LH, and that the PVN plays a role in these effects.

Animals↗
PubMed1997

In vitro characterisation of intramural neural pathways between the duodenum and the sphincter of Oddi of the brush-tailed possum.

The aims of this study were to determine if neural pathways between the duodenum and sphincter of Oddi are intramural, activated by duodenal electrical field stimulation (EFS) in vitro, and contain capsaicin-sensitive primary afferents. The possible involvement of cholinergic (muscarinic and/or nicotinic) and adrenergic receptors in these pathways were also investigated. Duodenal EFS (5-60 Hz, 70 V, 0.5 ms duration, 10 s train) at sites 2 cm oral and 2 cm anal to the sphincter of Oddi-duodenal junction produced frequency-dependent excitatory responses in the sphincter of Oddi, measured by manometry (n = 3). Excitatory responses from duodenal circular muscle were also evident. Tetrodotoxin (1 microM; n = 7) pretreatment abolished both sphincter of Oddi and duodenal responses to duodenal EFS. Crushing the duodenum between the site of stimulation and the sphincter of Oddi-duodenal junction also abolished sphincter of Oddi response. The sphincter of Oddi responses to duodenal EFS at the oral and anal sites were reduced by pretreatment with (i) atropine (100 nM: n = 7) to 19 +/- 6% (P < 0.05) and 22 +/- 8% (P < 0.05) of control respectively. (ii) hexamethonium (100 microM: n = 9) to 10 +/- 2% (P < 0.01) and 6.0 + 2.5% (P < 0.01) of control respectively and (iii) guanethidine (1 microM; n = 6) to 75 +/- 6% (P < 0.05) and 78 +/- 10% (P < 0.05) of control, respectively. Combined pretreatment with phentolamine and propranolol (both 1 microM; n = 7) was without effect, as was capsaicin (1 microM; n = 12) pretreatment. Excitatory intramural pathways between the sphincter of Oddi and the duodenum are primarily cholinergic in nature and contain an adrenergic component. Capsaicin-sensitive primary afferents are not involved.

Adrenergic Agents↗