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PubMed1994

Locus coeruleus noradrenergic neurons as a micturition center.

The micturition reflex arch is composed of an afferent pathway from the urinary bladder to the pontine micturition center via the pelvic nerve and spinal cord. The efferent pathway projects from the center to the bladder through the sacral parasympathetic center of intermediolateral column cells. The pontine micturition center is thought to be noradrenergic (NA) neurons in the locus coeruleus (LC) due to the following observations: (1) LC stimulation induces bladder contraction in cats, and this response is blocked by intrathecal application of alpha 1-adrenergic antagonist (prazosin), but not the alpha 2- nor beta-adrenergic antagonist. Although this contraction is not observed after NA depletion with reserpine, with subsequent i.v. injection of L-dopa a NA precursor induces recurrence of the response. (2) The micturition reflex induced by bladder distention is similarly reversed with alpha 1-adrenergic antagonist and chemical destruction of NA cells by injecting 6-hydroxydopamine in the LC. However, subsequently applied alpha 1-adrenergic agonist induces the contraction due to bladder distention. (3) LC stimulation elicits spike generation of sacral intermediolateral cells. Microiontophoretically applied alpha 1-adrenergic antagonist inhibits the LC stimulation-induced spikes of the neuron, which is not antidromically activated by pelvic nerve stimulation. However, spikes in neurons activated antidromically were not affected by the drug. This indicates that the former and latter neurons are interneuron and parasympathetic projecting neurons, respectively. The existence of NA terminals from the LC and alpha 1-adrenergic receptors in the intermediolateral column cells supports the concept that NA cells in the LC are units constituting the micturition center.

Animals↗
PubMed1996

Effects of moderate hypothermia on baroreflex and pulmonary chemoreflex heart rate response in decerebrate ferrets.

The effects on the baroreceptor reflexes and pulmonary reflexes of moderate immersion hypothermia (core temperature, 30.2 +/- 0.07 degrees C) have been investigated in the decerebrate ferret. Baroreflex sensitivity was estimated from the relationship between change in cardiac interval and change in systolic blood pressure following i.v. bolus injection of phenylephrine. The responses to phenylephrine in ferrets were best fitted by two linear slopes with an initial shallow slope, a, followed by a steeper slope, b. The slope or sensitivity of b was increased significantly by moderate cooling (n = 6 animals, 36 responses, P < 0.05). Pulmonary J-receptor reflex sensitivity was assessed by i.v. injection of phenylbiguanide (PBG), which evokes a dose-dependent bradycardia. The bradycardic response was unaltered by the hypothermia (n = 6 animals, 88 responses). Electrical stimulation of the right peripheral vagal nerve was employed to assess effects on the efferent components of the reflexes. The bradycardia, in response to stimulation, was significantly increased by moderate cooling at all stimulation frequencies (n = 8 animals, 88 responses, P < 0.001). Thus the results suggested that baroreceptor heart rate reflex sensitivity was enhanced by the moderate hypothermia. At least one component of the enhanced baroreflex response may be the result of changes in the efferent pathway of the reflex response. However, the absence of effect of PBG may indicate a differential afferent and efferent organization of pulmonary J-receptors compared with baroreceptors.

Animals↗
PubMed1982

Response of large hindlimb veins of dog to aortic arch chemoreceptor stimulation.

Experiments were performed in chloralose-anesthetized dogs to examine the reflex effects on tone in the saphenous vein of stimulating the aortic arch chemoreceptors. The saphenous vein was perfused with cooled (30 degrees C) aortic blood at constant flow, and perfusion pressure was measured. In 13 animals the aortic arch chemoreceptors were stimulated by injection of cyanide (0.1 mg/kg) into the root of the aorta. Cyanide caused a decrease (20 +/- 2 mmHg) in saphenous vein perfusion pressure and an increase (44 +/- 4) in aortic pressure. These changes that occurred subsequent to aortic root cyanide injections were abolished by vagotomy or section of the aortic nerves (afferent pathway); section of the lumbar sympathetic chain at L4 and L5 abolished the dilator response of the vein (efferent pathway) but did not alter the increase in aortic pressure. Four dogs were prepared for cardiopulmonary bypass and separate perfusion of the systemic circulation and the isolated aortic arch. Delivery of hypoxic-hypercapnic blood to the isolated aortic arch caused a dilation of the saphenous vein and an increase in systemic arterial perfusion pressure. From these results we conclude that cutaneous venomotor tone can be reflexly reduced through the aortic chemoreflex.

Animals↗
PubMed1983

On the sites of antitussive action of dl-glaucine phosphate.

The sites of antitussive action of dl-1,2,9,10-tetramethoxy-6a,alpha-aporphine phosphate (dl-glaucine phosphate, DL-832) were studied. It was assumed from the following results that DL-832 acts on the cough center per se. a) When DL-832 was given by the routes leading to the brain stem such as the vertebral artery and the cerebello-medullary cistern, far smaller doses were sufficient to obtain the same effect as that by i.v. administration. b) DL-832 showed neither effect on the afferent pathway for cough reflex nor influence on pulmonary stretch receptors. c) It exhibited practically no influence on the efferent pathways for cough reflex, that is, that for innervating respiratory muscle movement as well as that for controlling bronchial muscle tone. d) Decerebration exerted no influence on the antitussive effect. e) DL-832 definitely depressed the potentials of both the recurrent and internal intercostal nerves evoked by the superior laryngeal nerve stimulation. f) In deafferentated and decerebrate cats, DL-832 rather increased the spontaneous discharges of the phrenic nerve, whereas codeine decreased them.

Afferent Pathways↗
PubMed1998

Role of arterial baroreceptor function on cardiovascular adjustments to acute and chronic dynamic exercise.

Our series of experiments in rats, and other data of the literature, indicate that the arterial baroreceptors are actively involved in the reflex control of circulation during acute and chronic exercise. Although heart rate increases simultaneously with arterial blood pressure during an acute bout of dynamic exercise, the gain of the baroreflex bradycardia remains unchanged. Moreover, the more pronounced increase in mean arterial pressure during all exercise period observed in sino-aortic denervated rats, compared to sham-operated rats, suggests that the arterial baroreflex restrains the increase in blood pressure during dynamic exercise. However, the arterial baroreflex seems to have no influence on the development of exercise tachycardia. Exercise training can affect baroreflex bradycardia and tachycardia in the opposite direction, since decreased baroreflex bradycardia is observed despite increased baroreflex tachycardia. Since the increased baroreflex tachycardia may be attributed to an increased sensitivity of the afferent pathway of the baroreceptors, the attenuation of the baroreflex bradycardia is probably due to an impairment of the efferent pathway of the reflex. Finally, the decreased tonic sympathetic nerve activity produced by exercise training can be considered as one of the mechanisms involved in the attenuation of hypertension induced by exercise training.

Animals↗
PubMed1984

Reflex inhibition of insulin secretion: vagus nerve involvement via CNS.

The in situ brain-pancreas experimental model was used to investigate the influence of the vagus nerve during tonic direct central nervous system (CNS) inhibition of insulin secretion. Tonic CNS inhibition of insulin secretion was partially and transiently reversed following bilateral cervical vagotomy, suggesting that this inhibition includes a vagally mediated component. However, a substantial CNS inhibition of insulin secretion still occurred in the vagotomized preparations. This demonstrates that a major component producing tonic CNS inhibition of insulin secretion is independent of the vagus nerve and, furthermore, that it must be via direct sympathetic efferent pathways to the pancreas (because these preparations are functionally parasympathectomized via vagotomy). Further investigation into the vagus nerve involvement was carried out by stimulating either the afferent (central) or efferent (pancreatic) cut end of the vagus nerve of bilaterally vagotomized brain-pancreas preparations. Stimulation of the efferent vagus did not appreciably alter the effect of vagotomy on insulin secretion. However, when the central cut vagus was stimulated, the early transient reversal of tonic inhibition, which occurred in the vagotomized preparations, was totally reversed. This suggests that the vagally mediated early transient component of tonic CNS inhibition of insulin secretion is via afferent (central) neurons in the vagus nerve. These data demonstrate a reflex pathway for inhibition of insulin secretion that is comprised of vagal afferent neurons, the CNS, and sympathetic efferent neurons ending directly on the islets of Langerhans. It is tempting to speculate that gastrointestinal receptors exist that are capable of initiating this reflex inhibition of insulin secretion.

Animals↗
PubMed2003

Selective attention affects human brain stem frequency-following response.

Selective attention modifies long-latency cortical event-related potentials. Amplitudes are typically enhanced and/or latencies reduced when evoking stimuli are attended. However, there is controversy concerning the effects of selective attention on short-latency brain stem evoked potentials. The objective of the present study was to assess possible attention effects on the brain stem auditory frequency-following response (FFR) elicited by a periodic tone. Young adult subjects heard a repetitive auditory stimulus while detecting infrequent target stimuli in either an auditory or visual detection task. Five channels of high frequency electroencephalographic (EEG) activity were recorded along the scalp midline with the center electrode positioned at the vertex. The FFR was elicited by the repetitive tone during both tasks. There were significant individual differences in the electrode sites yielding maximum response amplitudes, but overall FFR amplitudes were significantly larger during the auditory attention task. These results suggest that selective attention in humans can modify signal processing in sensory (afferent) pathways at the level of the brain stem. This may reflect top-down perceptual preprocessing mediated by extensive descending (efferent) pathways that originate in the cortex. Overall, the FFR appears to be a robust indicator of early auditory neural processing and shows effects not seen in brain stem auditory evoked response studies employing transient (click) acoustic stimuli.

Acoustic Stimulation↗
PubMed1975

Interaction of the chemoreflex and the pulmonary inflation reflex in the regulation of coronary circulation in conscious dogs.

The interaction of chemoreflex and pulmonary inflation reflex control of the coronary circulation was examined in conscious dogs by comparing the responses to chemoreflex stimulation (intracarotid injection of nicotine) when ventilation was allowed to increase with those when ventilation was controlled. The responses were also compared with those elicited by both forced mechanical and spontaneous hyperinflation. When the heart rate was constant, intracarotidly administered nicotine induced an increase in the depth of respiration followed closely by an increase in late diastolic coronary flow from 48 +/- 2 to 106 +/- 8 ml/min and a reduction in late diastolic coronary resistance from 1.62 +/- 0.08 to 0.78 +/- 0.06 mm Hg/ml min-1. After beta-receptor and cholinergic blockade, a similar coronary dilation in response to nicotine occurred only when ventilation was allowed to increase. However, when ventilation was controlled, intracarotidly administered nicotine increased coronary resistance after combined beta-receptor and cholinergic blockade. The reflex coronary dilation was not observed after carotid sinus nerve section or after alpha-receptor blockade. Thus, nicotine stimulation of the carotid chemoreflex results in a striking coronary dilation that has two components. The minor component involves a chemoreflex with its efferent pathway in tthe vagi. The major component of coronary dilation follows an increase in the depth of respiration, and its efferent component appears to involve withdrawal of alpha-adrenergic constrictor tone. An almost identical period of reflex coronary dilation followed either forced mechanical or spontaneous hyperinflation in the conscious dog.

Adrenergic alpha-Antagonists↗
PubMed1997

Directed growth of early cortical axons is influenced by a chemoattractant released from an intermediate target.

Projection neurons throughout the mature mammalian neocortex extend efferent axons either through the ventrolaterally positioned internal capsule to subcortical targets or through the dorsally located midline corpus callosum to the contralateral cortex. In rats, the internal capsule is pioneered on E14, but the corpus callosum is not pioneered until E17, even though these two types of projection neurons are generated at the same time. Here we use axonal markers to demonstrate that early cortical axon growth is directed toward the nascent internal capsule, which could account for the timing difference in the development of the two efferent pathways. This directed axon growth may be due to a chemoattractant and/or a chemorepellent secreted by intermediate targets of cortical efferent axons, the nascent internal capsule, or the medial wall of the dorsal telencephalon (MDT), respectively. To test for these soluble activities, explants of E15 rat neocortex and intermediate targets were cocultured in collagen gels. Cortical axon outgrowth was directed toward the internal capsule, but outgrowth was nondirected and suppressed when cocultured with MDT, suggesting that the internal capsule releases a chemoattractant for cortical axons, whereas the MDT releases a chemosuppressant. Because the chemoattractant Netrin-1 is expressed in the internal capsule, we cocultured cortical explants with E13 rat floor plate, which expresses Netrin-1, or with Netrin-1-transfected or control-transfected 293T cells. Cortical axon growth was directed toward both floor plate and Netrin-1-transfected 293T cells, as it had been toward the internal capsule, but not toward control-transfected 293T cells. These findings suggest that early events in cortical axon pathfinding may be controlled by a soluble activity which attracts initial axon growth toward the internal capsule and that this activity may be due to Netrin-1.

Animals↗
PubMed1990

Involvement of amygdala pathways in the influence of post-training intra-amygdala norepinephrine and peripheral epinephrine on memory storage.

These experiments examined the role of two major amygdala afferent-efferent pathways--the stria terminalis (ST) and the ventral amygdalofugal pathway (VAF)--in mediating the effects, on memory storage, of post-training intra-amygdala injections of norepinephrine (NE) and subcutaneous (s.c.) injections of epinephrine (E). Rats with either ST lesions or VAF transections and sham-operated rats were trained on a one-trial step-through inhibitory avoidance task and immediately after training received intra-amygdala injections of NE or a buffer solution. Other groups of VAF-transected animals received post-training s.c. injections of E or saline. ST lesions blocked the memory-enhancing effect of intra-amygdala injections of a low dose of NE (0.2 microgram) as well as the amnestic effect of a high dose of NE (5.0 microgram). In contrast, VAF transections did not block the memory-enhancing effect of NE (0.2 microgram). However, VAF transections attenuated the memory-enhancing effect of s.c. injections of E: the effective dose of E was shifted from 0.1 to 0.5 mg/kg. These findings, considered together with previous evidence that ST lesions block the memory-enhancing effect of peripheral E injections, suggest that the VAF is involved in mediating the central influence of peripheral E on amygdala functioning, while the ST is involved in mediating amygdala influences on memory storage elsewhere in the brain.

Amygdala↗
PubMed1992

[Inhibitory effects of Hachimijiogan on micturition reflex via the locus coeruleus].

Pharmacological studies were undertaken to elucidate the role of Hachimijiogan in the micturition reflex via the locus coeruleus, using alpha-chloralose-anesthetized cats. Rhythmic contractions of the urinary bladder induced by continuous infusion of saline into the bladder were dose-dependently inhibited by intravenous injection of Hachimijiogan (10, 30 and 90 mg/kg), as well as flavoxate hydrochloride (1 and 3 mg/kg). In contrast, contraction of the urinary bladder elicited by electrical stimulation of the locus coeruleus was significantly suppressed by intravenous injection of flavoxate, but not affected by that of Hachimijiogan. These results suggest that Hachimijiogan acts on the afferent pathway from the urinary bladder to the locus coeruleus, thereby inhibiting the micturition reflex, while it has no effects on the efferent pathway from the locus coeruleus to the urinary bladder.

Animals↗
PubMed1989

The role of the lateral cortico-cortical prefrontal pathway in self-stimulation of the medial prefrontal cortex in the rat.

Effects of electrolytic and kainic acid lesions at several stereotaxic planes of the lateral cortico-cortical prefrontal efferent pathway on self-stimulation of the medial prefrontal cortex were investigated. Electrolytic bilateral lesion of the sulcal prefrontal cortex, the first terminal area of this pathway, produced no effects on self-stimulation of the medial prefrontal cortex. However, bilateral electrolytic lesion of this pathway at the rostral part of the external capsule produced a permanent abolition of self-stimulation of the medial prefrontal cortex. These effects seemed selective since operant behaviour to obtain water, similar to that performed for self-stimulation and used as a control, was not affected by the lesion except on the 1st, 3rd (P less than 0.01) and 5th (P less than 0.05) days postlesion. Interestingly, bilateral microinjections of kainic acid (10 nmol in 0.8 microliters) at the same stereotaxic planes of the external capsule where electrolytic lesion was produced, had no effects on self-stimulation. These results suggest that fibres-of-passage through the external capsule are responsible for the abolition of self-stimulation. Bilateral electrolytic lesion of the entorhinal cortex, one of the caudal terminal areas of this descending set of fibres, produced a short transient decrease of self-stimulation of the medial prefrontal cortex. These results are discussed on the basis that complex, rather than single circuits are involved in maintaining self-stimulation in this neocortical area.

Animals↗
PubMed1986

Effects of section of the medial efferent tracts (crossed and uncrossed) on cochlear frequency selectivity.

The cochlear innervation of guinea pigs was sectioned midway between the midline and the external side of the cochlear nucleus, in a rostrocaudal direction at the level of the floor of the fourth ventricle, to study the effects of medial efferent pathways on cochlear frequency selectivity estimated with tuning curves of single auditory nerve fibers. Single-unit tuning curves were affected by this type of efferent sectioning. Thus, the ipsi-lateral efferent system seems to be involved, through a tonic action, in the mechanisms responsible for high frequency cochlea selectivity.

Acoustic Stimulation↗
PubMed1989

The effects of knife cuts in the sub-paraventricular zone of the female rat hypothalamus on oestrogen-induced diurnal surges of plasma prolactin and LH, and circadian wheel-running activity.

To investigate the role of suprachiasmatic efferent connections in the expression of diurnal hormone rhythms, the efferent pathway from the suprachiasmatic nucleus (the putative circadian generator in the rat) to the subparaventricular zone (the main terminal area of suprachiasmatic efferents) was disrupted using bilateral horizontal knife cuts in ovariectomized oestrogen-treated rats. The position of the knife cut was assessed by observing its effect on vasoactive intestinal polypeptide immunoreactivity (a marker for suprachiasmatic efferents into the sub-paraventricular zone). The size of both the diurnal plasma LH and prolactin surges was markedly and consistently reduced over the 3-week period following the lesion in animals with a total deafferentation of the subparaventricular zone, compared with sham-operated animals or lesioned animals with an intact subparaventricular zone. When lesioned animals were grouped according to the presence or absence of damage to the preoptic area, no significant differences were found in the sizes of the plasma hormone surges. When similar knife cuts were given to animals whose activity cycles were observed, no significant effects were noted in the ability of the animals to synchronize to a light/dark regime or to free-run in constant light conditions. These results suggest that the suprachiasmatic nucleus influences the diurnal surges of plasma LH and prolactin in oestrogen-treated ovariectomized rats, initially by an interaction with the subparaventricular zone and not by a direct influence on gonadotrophin-releasing hormone neurones or other more rostral structures.

Animals↗
PubMed1986

Volitional movement is not preceded by cortical slow negativity in cerebellar dentate lesion in man.

Slow negative potential preceding voluntary self-paced middle finger extension, as recorded from scalp electrodes by backward averaging technique, was absent in two patients with dyssynergia cerebellaris myoclonica (Ramsay Hunt syndrome); but present in two patients with cerebellar cortical degeneration. As the main pathological lesion in Ramsay Hunt syndrome is in the dentate nucleus and its efferent pathway, the present results are in conformity with the experimental finding that the premotor and motor cortices receive strong inputs from the cerebellar efferent system.

Adolescent↗
PubMed1989

Signal processing in a simple vertebrate photoreceptor system: the teleost pineal organ.

The integrating circuitry and efferent pathways for neural signals evoked in the photosensory pineal organ by changes in ambient illumination have been investigated by a multidisciplinary approach. Intrapineal efferent neurons were identified by means of retrograde filling with horseradish peroxidase (HRP). In addition to several types of neurons, photoreceptor cells that emitted axons to the brain via the pineal tract were observed. The presence of several populations of local interneurons (putatively cholinergic, GABAergic and substance P-containing) and possible afferent (putatively noradrenergic and peptidergic) central innervations were established by means of immunocytochemistry. The anatomical substrate for processing of neural signals thus delineated, the responses of pineal sensory and neural elements to photic stimulation were investigated by means of intracellular recording. Successful recordings were followed by intracellular injection with HRP or Lucifer Yellow CH, for subsequent light or electron microscopical investigation. The recordings indicate the presence of at least two types of photoreceptor cells, that display morphological and physiological features of both retinal rods and cones. In addition, one type of (sign-conserving) interneuron was identified. The photosensory pineal organ thus possess an integrative neural circuitry that may be involved in the elaboration of neural signals to the brain, and/or in the local control of intrapineal functions, e.g. indoleamine synthesis.

Animals↗
PubMed1977

Hypothalamic influence on insulin and glucagon release in the rat.

Blood glucose, plasma insulin, and glucagon levels were measured in undisturbed and free-moving rats. The insulin and glucagon levels rise in the 1st min after the beginning of food ingestion, whereas the glucose level begins to increase only in the 3rd min if carbohydrate-rich food is eaten. This early rise in insulin and glucagon level is also observed under conditions in which carbohydrate-free food is eaten. A similar release of insulin and glucagon can be obtained by injection of 0.1 microgram of norepinephrine into the ventromedial hypothalamus, but the same injection made into the lateral hypothalamus causes release of insulin only, whereas injections in other hypothalamic areas are nearly without effect. Similar injections of isoproterenol did not cause changes in insulin, glucagon, and glucose levels. It is suggested that the early insulin and glucagon responses are of reflex origin and that the ventromedial and lateral hypothalamic areas are relay stations in the reflex pathways. The lack of effect of atropine to block the insulin and glucagon responses to noradrenergic stimulation of the ventromedial hypothalamus indicates that the efferent pathway is not cholinergic.

Animals↗