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PubMed2000

Mechanisms of the cutaneous vasodilator response to local external pressure application in rats: involvement of CGRP, neurokinins, prostaglandins and NO.

1. Local pressure-induced vasodilation (PIV) is a neural vasodilator response to non-nociceptive externally applied pressure in the skin, previously described in humans. We first determined whether PIV exists in rats and depends on capsaicin-sensitive fibres as it does in humans. We then examined the mediators involved in the efferent pathway of PIV. 2. Cutaneous blood flow was measured by laser Doppler flowmetry during 11.1 Pa s(-1) increases in local applied pressure in anaesthetized rats. The involvement of capsaicin-sensitive fibres in PIV was tested in rats treated neonatally with capsaicin. To antagonize CGRP, neurokinin-1, -2, or -3 receptors, different groups of rats were treated with CGRP(8 - 37), SR140333, SR48968 or SR142801, respectively. Prostaglandins involvement was tested with indomethacin treatment. To inhibit nitric oxide synthase (NOS) activity or specific neuronal NOS, rats were treated with N(G)-nitro-L-arginine or 7-nitroindazole, respectively. 3. PIV was found in rats, as in humans. PIV was abolished by neonatal treatment with capsaicin and by administration of CGRP(8 - 37) but remained unchanged with SR140333, SR48968 and SR142801 treatments. Prostaglandin inhibition resulted in a significant decrease in PIV. Inhibition of NOS abolished PIV, whereas inhibition of neuronal NOS caused a diminution of PIV. 4. These data suggest that PIV depends on capsaicin-sensitive fibres in rats, as in humans. It appears that CGRP plays a major role in the PIV, whereas neurokinins have no role. Furthermore, PIV involves a contribution from prostaglandins and depends on endothelial NO, whereas neuronal NO has a smaller role.

Animals↗
PubMed2006

Integrative control of the lower urinary tract: preclinical perspective.

Storage and periodic expulsion of urine is regulated by a neural control system in the brain and spinal cord that coordinates the reciprocal activity of two functional units in the lower urinary tract (LUT): (a) a reservoir (the urinary bladder) and (b) an outlet (bladder neck, urethra and striated muscles of the urethral sphincter). Control of the bladder and urethral outlet is dependent on three sets of peripheral nerves: parasympathetic, sympathetic and somatic nerves that contain afferent as well as efferent pathways. Afferent neurons innervating the bladder have A-delta or C-fibre axons. Urine storage reflexes are organized in the spinal cord, whereas voiding reflexes are mediated by a spinobulbospinal pathway passing through a coordination centre (the pontine micturition centre) located in the brainstem. Storage and voiding reflexes are activated by mechanosensitive A-delta afferents that respond to bladder distension. Many neurotransmitters including acetylcholine, norepinephrine, dopamine, serotonin, excitatory and inhibitory amino acids, adenosine triphosphate, nitric oxide and neuropeptides are involved in the neural control of the LUT. Injuries or diseases of the nervous system as well as disorders of the peripheral organs can produce LUT dysfunctions including: (1) urinary frequency, urgency and incontinence or (2) inefficient voiding and urinary retention. Neurogenic detrusor overactivity is triggered by C-fibre bladder afferent axons, many of which terminate in the close proximity to the urothelium. The urothelial cells exhibit 'neuron-like' properties that allow them to respond to mechanical and chemical stimuli and to release transmitters that can modulate the activity of afferent nerves.

Afferent Pathways↗
PubMed2001

Gaze shifts evoked by electrical stimulation of the superior colliculus in the head-unrestrained cat. II. Effect of muscimol inactivation of the caudal fastigial nucleus.

The medioposterior cerebellum [vermian lobules VI and VII and caudal fastigial nucleus (cFN)] is known to play a major role in the control of saccadic gaze shifts toward a visual target. To determine the relative contribution of the cFN efferent pathways to the brainstem reticular formation and to the superior colliculus (SC), we recorded in the head-unrestrained cat the effects of cFN unilateral inactivation on gaze shifts evoked by electrical microstimulation of the deeper SC layers. Gaze shifts evoked after muscimol injection still exhibited the typical qualitative features of normal saccadic gaze shifts. Nevertheless, consistent modifications in amplitude and latency were observed. For ipsiversive movements (evoked by the SC contralateral to the inactivated cFN), these changes depended on the locus of stimulation on the motor map: for the anterior 2/3 of the SC, amplitude increased and latency tended to decrease; for the posterior 1/3 of the SC, amplitude decreased and latency increased. For the contraversive direction, amplitude moderately decreased and latency tended to increase for all but the caudal-most stimulated SC site. These modifications of SC-evoked gaze shifts during cFN inactivation differed from the ipsiversive hypermetria/contraversive hypometria pattern observed for visually triggered gaze shifts recorded during the same recording sessions. We conclude that (i) the topographical organization of gaze shift amplitude in the deeper SC layers is influenced by the cerebellum and is either severely distorted or demonstrates an amplitude reduction during inactivation of the contralateral or ipsilateral cFN, respectively; (ii) gaze shifts evoked by SC microstimulation and visually triggered gaze shifts either rely on distinct cerebellar-dependent control processes or differ by the location of the caudal-most active SC population. We present a functional scheme providing several predictions regarding the modulatory influence of the cerebellum on SC neuronal activities and on the topographical organization of fastigial-SC projections.

Acceleration↗
PubMed2003

Neurons of the rat preoptic area and the raphe pallidus nucleus innervating the brown adipose tissue express the prostaglandin E receptor subtype EP3.

The major effector organ for thermogenesis during inflammation or experimental pyrogen-induced fever in rodents is the brown adipose tissue (BAT). Prostaglandin E2 (PGE2) microinjection into the medial preoptic area (POA) of rats leads to hyperthermia through an increase in BAT thermogenesis and induces pyrogenic signal transmission towards the raphe pallidus nucleus (RPa), a brainstem nucleus known to contain sympathetic premotor neurons for BAT control. The medial POA has a high expression of prostaglandin E receptor subtype EP3 (EP3R) on POA neurons, suggesting that these EP3R are main central targets of PGE2 to mediate BAT thermogenesis. To reveal central command neurons that contain EP3R and polysynaptically project to the BAT, we combined EP3R immunohistochemistry with the detection of transneuronally labelled neurons that were infected after injection of pseudorabies virus into the BAT. Neurons double-labelled with EP3R and viral surface antigens were particularly numerous in two brain regions, the medial POA and the RPa. Of all medial POA neurons that became virally infected 71 h after BAT inoculation, about 40% expressed the EP3R. This subpopulation of POA neurons is the origin of a complete neuronal chain that connects potential PGE2-sensitive POA neurons with the BAT. As for the efferent pathway of pyrogenic signal transmission, we hypothesize that neurons of this subpopulation of EP3R expressing POA neurons convey their pyrogenic signals towards the BAT via the RPa. We additionally observed that two-thirds of those RPa neurons that polysynaptically project to the interscapular BAT also expressed the EP3R, suggesting that RPa neurons themselves might possess prostaglandin sensitivity that is able to modulate BAT thermogenesis under febrile conditions.

Adipose Tissue, Brown↗
PubMed1997

Acute neuronal and vascular changes following unilateral cerebellar pedunculotomy in the neonatal rat.

During development of the central nervous system (CNS) both deafferentation and axotomy induce increased neuronal death and result in a smaller brain with diminished function at maturity. Unilateral cerebellar pedunculotomy has been used as a model to study the relative importance of these 2 types of lesion on the survival of developing CNS neurons. Within the cerebellum, unilateral pedunculotomy causes deafferentation of the hemicerebellum and axotomy in the efferent pathway from the ipsilateral deep cerebellar nuclei. This results in a smaller hemicerebellum with normal cortical laminae but no extracerebellar outflow. In order to identify the sequence of events which leads to this altered structure and therefore to understand the relative importance of afferent versus target-derived trophic support, unilateral cerebellar pedunculotomy was performed on neonatal rat pups, aged between 1 and 3 days. The cerebella were analysed for histological and vascular changes after survival times of 0, 3, 6, 9, 12, 18, 21, 24 and 48 h. The results show that the effects of axotomy on the deep cerebellar nuclear neurons begin within 3 h of the lesion and apoptotic neuronal degeneration occurs within 48 h. However, the cerebellar cortical neurons continue to undergo normal histological development for at least 48 h after deafferentation. In addition, since ischaemia induces similar effects, a study of the vascular tree was made. The results indicate that the pedunculotomy does not alter the blood supply to the cerebellum, nor induce ischaemia of the cerebellar neurons. From this it may be hypothesised that target-derived trophic support is more crucial for the survival of immature neurons than is the trophic effect of afferent input.

Afferent Pathways↗
PubMed2002

Trigeminocardiac reflex: a unique case of recurrent asystole during bilateral trigeminal sensory root rhizotomy.

BACKGROUND: The trigeminocardiac reflex is the sudden-onset of dysrhythmia and hypotension during manipulation of any of the branches of the trigeminal nerve. The trigeminal nerve and cardioinhibitory vagus nerve constitute the afferent and efferent pathways in the reflex arc. The trigeminocardiac reflex has been reported to occur during craniofacial surgery, balloon-compression rhizolysis of the trigeminal ganglion, and tumour resection in the cerebellopontine angle. PATIENT & METHOD: A 2-year-old male patient with haemangioma near the sella turcica underwent rhizotomies of both sides of the dorsal sensory roots, of the trigeminal nerves for palliation of intractable trigeminal pain. RESULTS: In this report, we experienced two unexpected episodes of asystole after transection of the sensory roots of the trigeminal nerves. CONCLUSION: Sectioning of the intracranial dorsal sensory root of the trigeminal nerve provides clear evidence of the central role of the trigeminal nerve as the afferent pathway of the trigeminocardiac reflex arc.

Aged↗
PubMed1988

Innervation of the microcirculation.

Neurogenic control of the peripheral circulation is accomplished by alterations in nerve discharge to the pre- and postcapillary vascular network in the various organs. The postganglionic sympathetic adrenergic nerves constitute the most important efferent pathway for neural control. The physiologic response of the microvasculature to neural influences depends on a number of factors: the pattern of distribution of the innervation to the microvessels is one of the more important determinants. In addition to its influence on the contractile state of vascular smooth muscle, the adrenergic nerves also have a trophic influence on the smooth muscle cells. Following surgical denervation of a vascular bed, the adrenergic nerve terminals degenerate, and subsequently reinnervate, the vasculature. During the period following denervation, a number of functional and morphologic changes occur in the smooth muscle. This review emphasizes those aspects of the structure and function of adrenergic nerves that may have particular relevance for microsurgery.

Adrenergic Fibers↗
PubMed1983

The nervous control of rat glucagon secretion in vivo.

In order to study the efferent pathways of the nervous regulation of rat A and B cells, portal blood samples were obtained in vivo without interruption of the blood flow. Glucagon, insulin and catecholamines were determined and hepatic blood flow (EHBF) was estimated by a Brome-Sulfone-Phtaleine extraction method. Carotid blood pressure was monitored and a normal volaemia was maintained. Stimulation of the right vagus nerve increased EHBF and the releases of glucagon and insulin. Stimulation of splanchnic nerve increased the glucagon and catecholamine secretions and decreased that of insulin. Acute hypovolaemia as induced by blood withdrawal, caused hormonal consequences similar to those of splanchnic stimulation. It is suggested that the nervous control of pancreatic islets plays an important role in the rat species. Assessment of the haemodynamic status is critical for the valid interpretation of pancreatic hormone concentrations in experimental conditions. A sympathetic stimulation can account for the high glucagon and relatively low insulin secretions which characterize the hormonal pattern of stress.

Animals↗
PubMed1999

Influence of descending forebrain projections on processing of acoustic signals and audiomotor integration in the anuran midbrain.

We tested the role of descending projections for auditory processing and audiomotor integration in the anuran torus semicircularis. Intracellular recordings were made from isolated brain preparations, impaled neurons were stained. Auditory neurons responded to electrical stimulation of striatum and/or dorsal thalamus, they integrated forebrain and auditory nerve inputs. High frequency stimulation in striatum or thalamus changed the auditory response of torus neurons located in the laminar subnucleus. Our results suggest that the laminar nucleus is the primary target of forebrain projections, which provides a basis for modulation of acoustically guided behaviour.

Animals↗
PubMed2005

Alteration of gastric myoelectrical and autonomic activities with audio stimulation in healthy humans.

OBJECTIVE: Cold or emotional stress was reported to affect gastric myoelectrical activity. The aim of this study was to investigate the effects of music or noise on gastric myoelectrical activity and autonomic function in healthy volunteers. MATERIALS AND METHODS: The study was performed in 10 fasted healthy volunteers and included 30 min at baseline, 30 min of classical music via headphones and 30 min of loud household noises via headphones. The electrogastrogram (EGG) readings were recorded simultaneously with the electrocardiogram (ECG) recording. RESULTS: Both classical music and noise altered the regularity of gastric slow waves. The percentage of normal 2-4 cycles/min (cpm) waves was reduced from 77.9 +/- 4.7% at baseline to 66.9 +/- 5.4% during music (p < 0.006) and 67.7 +/-5.4% during noise (p < 0.05). The reduction was attributed to a significant increase in bradygastria (15.8 +/- 3.9% versus 9.8 +/- 2.6%, p < 0.04) with the music and a significant increase in arrhythmia (7.4 +/- 1.6% versus 2.0 +/- 1.1%, p < 0.02) with the noise. The dominant frequency and power of the EGG were, however, not altered with either music or noise. Neither music nor noise had any effect on the autonomic function assessed by the heart rate variability. CONCLUSIONS: Audio stimulation, with both music and noise, alters the rhythmicity of gastric slow waves. Classical music seems to increase bradygastria, whereas, household noise may increase arrhythmia. The effect of audio stimulation on the gastric slow wave does not seem to involve sympathetic or vagal efferent pathways assessed by the spectral analysis of heart rate variability.

Acoustic Stimulation↗
PubMed2003

Nonvisual photoreceptors in arthropods with emphasis on their putative role as receptors of natural Zeitgeber stimuli.

In various insect and arachnid species, three different types of photoreceptors that do not serve image processing have been discovered and analyzed by means of neurobiological methods: They can be found for example: (1) as lamina and lobula organs (LaOs and LoOs) next to the optic neuropils in the optic lobes of holo- and hemimetabolous insects; (2) inside the last ganglia of the cord of the scorpion and a marine midge; and (3) as modified visual photoreceptors in metamorphosized larval stemmata and the lateral eyes of scorpions, which have been compound eyes in fossil scorpion relatives. Imnunocytology with various antibodies against proteins of the phototransduction cascade, the rhabdom turnover cycle and neurotransmitters of afferent and efferent pathways, was combined with light- and ultrastructural investigations in well-defined adaptational states, in order to study their photoreceptive function and neuronal wiring. Pilot chronobiological experiments with a newly developed twilight simulating lamp, behavioral studies, and model calculations provide evidence that these photoreceptors may well serve a role in the complex task of detecting time cues out of natural dawn and dusk.

Animals↗
PubMed1986

Inhibition of acute experimental allergic encephalomyelitis in mice by colchicine.

Colchicine was found to inhibit the clinical and histopathological manifestations of monophasic experimental allergic encephalomyelitis in mice. For inhibition of actively induced disease, inoculation of colchicine at the time of encephalitogenic challenge was found to be most effective. In adoptive transfer experiments, lymph node cells (LNC) from colchicine treated donors failed to transfer the disease. Additionally, colchicine treatment of recipients receiving an otherwise disease-inducing level of sensitized LNC prevented the development of disease. Experiments involving delayed-type hypersensitivity expression support an inhibitory role for the drug on event(s) of the efferent pathway of the cellular immune response.

Animals↗
PubMed1976

Enhanced pressor response to noradrenaline in patients with cervical spinal cord transection.

Arterial blood pressure, heart-rate and the electrocardiogram were recorded in subjects tetraplegic from cervical spinal cord transections, and in control subjects, before, during and after intravenous infusions of 1-noradrenaline. Over a wide range of doses the blood pressure rose much more in the tetraplegics than in the controls. Circulating noradrenaline during infusion did not significantly differ between the two groups. The findings indicate that tetraplegic subjects have an enhanced pressor response to noradrenaline infusions. Such a response therefore does not necessarily indicate post-ganglionic sympathetic denervation. The observed responses in the tetraplegics may in part be due to exaggerated adrenergic receptor responses, but the main cause is likely to be the loss of those baroreceptor reflexes with sympathetic efferent pathways.

Adult↗
PubMed1976

Interferon and delayed-type hypersensitivity to a viral antigen.

Delayed hypersensitivity to Newcastle disease virus was measured with use of a footpad test in mice. When tissue culture interferon was administered 24 hr before sensitization, footpad swelling upon subsequent challenge with the virus was significantly decreased. In animals already sensitized to the virus, footpad swelling was similarly decreased if interferon was administered a few hours before footpad challenge. This result indicates that interferon can affect both the afferent and the efferent pathways of delayed hypersensitivity to Newcastle disease virus and is in agreement with previous results obtained with nonviral antigens.

Animals↗
PubMed2002

The underlying basis for obesity: relationship to cancer.

An increase in the risk of cancer is one of the consequences of obesity. The predominant cancers associated with obesity have a hormonal base and include breast, prostate, endometrium, colon and gallbladder cancers. As the basis for understanding the problem of obesity has advanced, a number of new ideas have emerged about the relationship of obesity to cancer. The conversion of androstenedione secreted by the adrenal gland into estrone by aromatase in adipose tissue stroma provides an important source of estrogen for the postmenopausal woman. This estrogen may play an important role in the development of endometrial and breast cancer. Of interest is that experimental animals lacking aromatase or the estrogen receptor alpha are obese. Leptin is one of the many products produced by fat cells and has given rise to the ideas that the fat cell is an endocrine cell and that adipose tissue is an endocrine organ. The increased release of cytokines from this tissue may play a role in the inflammatory state that is associated with obesity. The gut also plays an important role in signaling satiety in response to food intake. Colon cancer is an important human disease, and experimental mice lacking gastrin are obese and have an increased risk of developing colon cancer in response to carcinogenic drugs. Efforts to control obesity through preventive strategies and treatment can be expected to have a benefit in reducing the risk of cancer.

Adipose Tissue↗
PubMed1993

Elevated resting heart rate in rheumatoid arthritis: possible role of physical deconditioning.

Thirty-four patients with RA, 76 diabetic subjects (DM) and 67 healthy controls (CR) were studied in order to study cardiovascular autonomic function in RA. Valsalva manoeuvre, deep breathing test and active orthostatic test were used. Resting heart rate (resting HR) was markedly elevated in the RA and DM groups. Therefore, the groups were compared using analysis of variance with age and resting HR as covariates. The analyses showed no differences in cardiovascular responses between the RA group and CR group but cardiovascular responses were significantly diminished in the DM group compared with both the CR group and RA group. Our data indicate that the parasympathetic efferent pathway mediating cardiovascular reflexes via the nervus vagus is intact in RA. Thus elevated resting HR in RA does not seem to be due to peripheral parasympathetic damage. Physical deconditioning may explain the elevation of resting HR in patients with RA.

Adult↗
PubMed1981

Sensorimotor electroencephalogram rhythmic activity: a functional gate mechanism.

Neurophysiological evidence for a negative feedback loop in somatosensory thalamic nuclei has provided a basis for understanding the origins of rhythmic activity in the electroencephalogram (EEG) of sensorimotor cortex. Studies reviewed here suggest that state-specific activation of this mechanism is responsible both for a variable pattern of rhythmic frequencies during wakefulness and the spindle burst pattern during sleep. It is proposed further that these rhythms index immobility and a common set of physiological changes in sensorimotor function, including reduced excitability in both afferent and efferent pathways. It is hypothesized, therefore, that the closing of a thalamic "inhibitory gate" is indicated by the occurrence of these rhythms. While a greater resolution of specific relationships is necessary, the study of these EEG patterns clearly provides a measure of complex physiological events in the nervous system, and can be also useful in identifying functional abnormalities.

Animals↗
PubMed2002

Upright posture reduces thermogenesis and augments core hypothermia.

UNLABELLED: We recently reported that baroreceptor-mediated reflexes modulate thermoregulatory vasoconstriction during lower abdominal surgery. Accordingly, we examined the hypothesis that postural differences and the related alterations in baroreceptor loading similarly modulate the thermogenic (i.e., shivering) response to hypothermia in humans. In healthy humans (n = 7), cold saline was infused IV (30 mL/kg at 4 degrees C) for 30 min to decrease core temperature. Each participant was studied on 2 separate days, once lying supine and once sitting upright. Tympanic membrane temperature and oxygen consumption were monitored for 40 min after each saline infusion. The decrease in core temperature upon completion of the infusion in the upright posture position was 1.24 degrees C +/- 0.07 degrees C, which was significantly greater than the 1.02 degrees C +/- 0.06 degrees C seen in the supine position. The core temperature was reduced by 0.59 degrees C +/- 0.07 degrees C in the upright position but only by 0.37 degrees C +/- 0.05 degrees C in the supine position when the increase in oxygen consumption signaling thermogenic shivering occurred. Thus, the threshold temperature for thermogenesis was significantly less in the upright than the supine position. The gain of the thermogenic response did not differ significantly between the positions (363 +/- 69 mL. min(-1). degrees C(-1) for upright and 480 +/- 80 mL. min(-1). degrees C(-1) for supine). The skin temperature gradient was significantly larger in the upright than in the supine posture, suggesting that the peripheral vasoconstriction was augmented by upright posture. Plasma norepinephrine concentrations increased in response to cold saline infusion under both conditions, but the increase was significantly larger in the upright than in the supine posture. Baroreceptor unloading thus augments the peripheral vasoconstrictor and catecholamine response to core hypothermia but simultaneously reduces thermogenesis, which consequently aggravated the core temperature decrease in the upright posture. IMPLICATIONS: Upright posture attenuates the thermogenic response to core hypothermia but augments peripheral vasoconstriction. This divergent result suggests that input from the baroreceptor modifies the individual thermoregulatory efferent pathway at a site distal to the common thermoregulatory center or neural pathway.

Adult↗