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Biomedical subjects

J Ciriello

Publications and source records attributed to J Ciriello.

At least 91 records · Page 5Linked to original sources
PubMed1985

2-Deoxyglucose uptake in the central nervous system during systemic hypercapnia in the peripherally chemodenervated rat.

Changes in 2-deoxyglucose (2-DG) uptake in the central nervous system during systemic hypercapnia were determined by the [3H]2-DG autoradiographic method in peripherally chemodenervated rats. Autoradiographs were made from serial transverse sections of the brain and analyzed by a computer-based interactive image processing system for areas having increases or decreases in metabolic activity compared with control animals. The most pronounced change shown by autoradiographs of the hypercapnic animals was a generalized decrease in the metabolism of the gray matter throughout the central nervous system with respect to the normocapnic controls. However, several central structures showed evidence of either no change or an increased metabolism in the hypercapnic animals. In the brain stem these areas were localized to the ventrolateral region of the nucleus of the solitary tract rostral to the obex, around the region of the nucleus retroambiguus, in a region of the ventrolateral medullary reticular formation extending rostrally from the obex to the level of the intramedullary rootlets of the facial nerve, in the region of the ventral nucleus raphe pallidus, and in the region of the lateral parabrachial nucleus. In the diencephalon these regions included the supraoptic nucleus and the dorsal hypothalamic area, extending into the caudal portion of the paraventricular nucleus. The thoracolumbar cord showed activation of the lateral aspects of the dorsal horns, the region of lamina X and the region of the intermediolateral nucleus. These data may be interpreted as a functional map of the central structures activated in hypercapnia in the peripheral chemodenervated rat. It appears likely that these structures are involved in mediating the cardiorespiratory responses associated with the activation of central chemoreceptors by the increased carbon dioxide concentrations.

Animals↗
PubMed1985

An anomalous vagorenal reflex pathway in the cat.

Although physiological investigations support the view that the innervation to the kidney is primarily sympathetic in origin, there is anatomic evidence suggesting direct vagal projections to the kidney. We examined electrophysiologically the possibility that neural connections exist between the cervical vagus and renal nerves. Electrical stimulation of the peripheral segment of the cut cervical vagus evoked electrical activity in the central segment of cut renal nerve of chloralose-anesthetized, paralyzed cats. The evoked potentials (vagorenal responses) displayed components with peak latencies of about 50, 120, and 500 ms. Another peak at about 175 ms was also seen in some cases. In addition, a period of postexcitatory depression occurred between approximately 180 and 400 ms after delivery of the stimulus. Evoked responses were recorded in the contralateral as well as the ipsilateral renal nerves. In contrast, stimulation of the central cut end of renal nerves did not elicit responses in the cervical vagus. Vagorenal responses were not altered by cutting the subdiaphragmatic vagus indicating that the abdominal vagus was not involved in this response. Electrical activity in renal nerves elicited by vagal stimulation could be eliminated by either ganglionic blockade or by cutting or cooling the splanchnic nerves. Finally, supraspinal ischemia abolished the vagorenal response. These data suggest that a vagorenal reflex pathway exists and that the potentials recorded in renal nerves are due to activation of aberrant sensory fibers traveling from the peripheral segment of the cut cervical vagus to the central nervous system, where they excite a sympathetic efferent pathway to the kidney.

Animals↗
PubMed1985

Effect of paraventricular nucleus lesions on cardiovascular responses elicited by stimulation of the subfornical organ in the rat.

It has recently been reported that stimulation of the region of the subfornical organ (SFO) elicits an increase in arterial pressure. However, the mechanisms and forebrain neural circuitry that are involved in this cardiovascular response have not been elucidated. The present study was done in urethane-anaesthetized rats to determine whether selective activation of SFO neurons elicit cardiovascular responses and whether these responses were mediated by a pathway involving the paraventricular nucleus of the hypothalamus (PVH). Stimulation sites which required the lowest threshold current (30 microA) to elicit a pressor response and at which the largest rise in mean arterial pressure (MAP; 22 +/- 2 mmHg) was elicited at a constant current intensity (150 microA) were histologically localized in the region of the SFO. Short (mean peak latency; 4 +/- 2 s) and long (mean peak latency; 61 +/- 8 s) latency increases in MAP were observed during and after electrical stimulation of the SFO, respectively. Cardiac slowing accompanied the short latency pressor response and cardioacceleration was observed in most (57%) of the cases to accompany the late pressor response. Microinjection of L-glutamate into the SFO consistently elicited cardiovascular responses qualitatively similar to those observed during electrical stimulation. Ganglionic blockade abolished the short latency increase in MAP and the accompanying bradycardia. However, the long latency pressor and cardioacceleratory responses were not altered by ganglionic blockade and adrenalectomy. Selective bilateral electrolytic or kainic acid lesions of the region of the PVH significantly attenuated the cardiovascular responses elicited by stimulation of the SFO. These data suggest that activation of neurons in the SFO elicit cardiovascular responses partially mediated by sympathetic outflow through a neural pathway involving the PVH.

Adrenalectomy↗
PubMed1985

Afferent renal nerve stimulation excites supraoptic vasopressin neurons.

Single-unit recording experiments were performed in pentobarbital-anesthetized rats to investigate the effects of afferent renal nerve (ARN) stimulation on the activity of neurosecretory vasopressin cells of the supraoptic nucleus (SON). Neurosecretory SON cells were identified by antidromic invasion from the neurohypophysis and classified either as vasopressin (AVP) or oxytocin (OXY) secreting on the basis of their spontaneous activity patterns and response to activation of arterial baroreceptors. Fifty-three spontaneously active units were identified bilaterally in the SON: 40 putative AVP and 13 putative OXY neurons. Most putative AVP neurons (14/14 contralateral, 18/26 ipsilateral) were excited by ARN stimulation (mean onset latency 189 +/- 5 ms, mean response duration 237 +/- 17 ms). In contrast, ARN stimulation had no effect on the firing frequency of the 13 putative OXY neurons. These data indicate that sensory information originating in the kidney selectively alters the activity of SON AVP neurons and suggest that afferent information from the kidney is important in the coordination of neural and hormonal activity concerned with body fluid balance and the regulation of arterial pressure.

Afferent Pathways↗
PubMed1984

Electrophysiological identification of neurons in the parabrachial nucleus projecting directly to the hypothalamus in the rat.

Experiments were done in urethane anesthetized rats to identify single units in the region of the parabrachial nucleus (PBN) projecting directly to 'cardiovascular' responsive sites in either the paraventricular nucleus of the hypothalamus (PVH) or the supraoptic commissure and nucleus (SOC-SON) region. Fifty-five single units were antidromically activated in the ipsilateral PBN by electrical stimulation of either the PVH (n = 27) or SOC-SON region (n = 28) with latencies corresponding to conduction velocities of 0.3-5.1 m/s. The axons of PBN units projecting to the PVH conducted at significantly slower velocities (0.5 +/- 0.04 m/s) than those projecting to the SOC-SON region (1.6 +/- 0.25 m/s). These data suggest that ascending fibers from the PBN to the PVH are unmyelinated, whereas those to the SOC-SON region are primarily a little myelinated. In addition, since the PBN is known to receive cardiovascular and visceral afferent inputs, it is suggested that these neurons likely function in relaying this afferent information to hypothalamic areas involved in autonomic regulation.

Animals↗
PubMed1984

Lesions of the paraventricular nucleus alter the development of spontaneous hypertension in the rat.

The role of the paraventricular nucleus of the hypothalamus (PVH) in the development of hypertension was determined after bilateral electrolytic or sham lesions of this structure in 4-5-week-old male spontaneously hypertensive rats (SHR). The average arterial pressure in the PVH-lesioned group was significantly lower compared to sham-lesioned animals during the first 3 weeks after the PVH lesions. At 9 weeks of age the arterial pressures of the PVH-lesioned animals increased, but remained significantly lower than those of the sham-operated animals of the same age. This difference in arterial pressures was observed to 16 weeks of age. Heart rate was significantly reduced by PVH lesions up to 5 weeks after the lesions, at which point the heart rate tended towards the control values of the sham-lesioned animals. These data have demonstrated that the region of the PVH is important in the initial phase of the development of hypertension and in the full expression of the hypertension in the SHR, and provide evidence of a central mechanism in the hypertensive process in the SHR.

Animals↗
PubMed1984

Electrophysiological identification of neurons in ventrolateral medulla sending collateral axons to paraventricular and supraoptic nuclei in the cat.

Experiments were done in chloralosed, paralyzed and artificially ventilated cats to identify single units in the ventrolateral medulla (VLM) that send collateral axons directly to the region of the paraventricular (PVH) and supraoptic (SON) nuclei, and responding to peripheral inputs carrying cardiovascular afferent information. Twenty-six single units were antidromically activated in the VLM to stimulation of both the PVH and SON, and in each case the antidromic potential evoked by stimulation of one site was cancelled by stimulation of the other site. These units responded with latencies corresponding to conduction velocities of 5.1 +/- 0.4 m/s. Of these 26 units, 10 responded orthodromically to stimulation of either the carotid sinus or aortic depressor nerves. These data have demonstrated the existence of VLM neurons which send collateral axons to the PVH and SON and have provided evidence for their role in mediating cardiovascular afferent information directly to hypothalamic regions involved in autonomic and neuroendocrine regulation.

Animals↗
PubMed1984

Paraventricular nucleus of the hypothalamus: an electrophysiological investigation of neurons projecting directly to intermediolateral nucleus in the cat.

Experiments were done in chloralosed, paralyzed and artificially ventilated cats to identify electrophysiologically single units in the paraventricular nucleus of the hypothalamus (PVH) projecting directly to 'cardiovascular' responsive sites in the region of the intermediolateral nucleus (IML) in the upper thoracic cord. Action potentials evoked antidromically by electrical stimulation of the IML were recorded from 41 histologically verified single units in the PVH. Single units responded with a mean latency of 43.7 +/- 5.6 ms (range, 16-230 ms) corresponding to a mean conduction velocity of 4.1 +/- 0.2 m/s (range, 0.6-7.4 m/s). Single units were located primarily in the medial aspect of the anterior component, and in the anteromedial aspect of the dorsal component of the PVH. These data provide electrophysiological evidence of a direct pathway consisting of unmyelinated and small myelinated fibers, from neurons in the PVH to the IML, and suggest that this pathway is involved in the control of the circulation.

Animals↗
PubMed1984

Direct pathway from neurons in the ventrolateral medulla relaying cardiovascular afferent information to the supraoptic nucleus in the cat.

In chloralose anesthetized cats experiments were done to electrophysiologically identify neurons in the ventrolateral medulla (VLM) which relay cardiovascular afferent information directly to the supraoptic nucleus (SON). Action potentials elicited antidromically by electrical stimulation of the SON were recorded from 69 histologically verified single units in the VLM. Single units responded with latencies corresponding to conduction velocities of 7.8 +/- 0.6 m/s. Of these units 26 were excited orthodromically by stimulation of the buffer nerves; 12 responded to stimulation of only the carotid sinus nerve, 7 responded to stimulation of only the aortic depressor nerve, and 7 responded to both buffer nerves. The axons of VLM units that responded to buffer nerves conducted at a significantly slower velocity than those of non-responsive units (5.7 +/- 0.4 and 9.1 +/- 0.8 m/s, respectively). These data provide electrophysiological evidence of two different populations of VLM neurons which project directly to the SON, and suggest that the direct pathway from the VLM to the SON is involved in the release of vasopressin by SON neurons during activation of baroreceptor and chemoreceptor afferent fibers.

Animals↗
PubMed1984

Ventrolateral medullary neurons relay cardiovascular inputs to the paraventricular nucleus.

Horseradish peroxidase (HRP) and single-unit recording experiments were done in cats to identify neurons in ventrolateral medulla (VLM) that project directly to the paraventricular nucleus (PVH) and relay cardiovascular information from carotid sinus (CSN) and aortic depressor (ADN) nerves. After diffusion of HRP into the PVH, retrogradely labeled neurons were observed in the VLM. The region of the VLM containing HRP-labeled neurons was then explored for single units antidromically activated by stimulation of the PVH in chloralosed, paralyzed, and artificially ventilated cats. These units were then tested for their responses to stimulation of the CSN and ADN. Antidromic potentials were recorded from 100 units in the VLM. Of these units, 65% were orthodromically excited by stimulation of buffer nerves; 28 by only CSN, 19 by only ADN, and 18 by both CSN and ADN. The axons of antidromically activated units responding to buffer nerves conducted at slower velocities than those of nonresponsive units. These data demonstrate that VLM neurons projecting directly to PVH integrate cardiovascular afferent information and suggest that these VLM neurons may be involved in the control of the activity of magnocellular neurosecretory neurons in the PVH during activation of baroreceptor and chemoreceptor afferent fibers.

Action Potentials↗
PubMed1984

Chemoreceptor and baroreceptor inputs to ventrolateral medullary neurons.

Recording experiments were done in chloralose-anesthetized, paralyzed, and artificially ventilated cats to identify single units in the ventrolateral medulla (VLM) projecting directly to the region of the intermediolateral nucleus of the spinal cord (T2) and responding to selective activation of peripheral chemoreceptors (sodium cyanide, 20-60 micrograms in 0.1-0.3 ml saline into medial thyroid artery) and baroreceptors (phenylephrine, 2 micrograms/kg iv). The firing frequency of 49 of the 81 antidromically identified single units was altered by activation of the peripheral cardiovascular receptors. Of these responsive units, 25 responded only to activation of chemoreceptors (17 excited and 8 inhibited), 20 responded in various combinations to activation of both chemo- and baroreceptors, and 4 responded only to activation of baroreceptors. In addition, units that altered their firing frequency during baroreceptor activation (n = 24) responded in the opposite direction to baroreceptor unloading (carotid arterial occlusion). These results suggest that neurons in the VLM are components of bulbospinal sympathoexcitatory and -inhibitory pathways that receive cardiovascular afferent information and in turn influence vasoconstrictor and cardioacceleratory neurons in the intermediolateral nucleus of the upper thoracic cord.

Animals↗
PubMed1983

Metabolic alterations in the hypothalamus of the Brattleboro rat demonstrated with cytochrome oxidase histochemistry.

Metabolic activity in the hypothalamus of homozygous and heterozygous Brattleboro rats and Long-Evans control rats was studied using cytochrome oxidase histochemistry. Increased metabolic activity was observed in the paraventricular nucleus (PVH), supraoptic nucleus (SON) and nucleus circularis (NC) of homozygous Brattleboro rats, and in the PVH of heterozygous rats. These results suggest that the metabolic activity of PVH and SON neurons is altered because of the inability of magnocellular neurosecretory neurons to produce vasopressin. In addition, the hyperactivity of neurons in the NC is probably related to the chronic dehydration present in these animals.

Animals↗
PubMed1983

Cardiovascular afferent inputs to neurons in the ventrolateral medulla projecting directly to the central autonomic area of the thoracic cord in the cat.

Experiments were done in chloralosed, paralyzed and artificially ventilated cats to identify single units in the ventrolateral medulla (VLM) projecting directly to the central autonomic area of the thoracic cord (CA) and responding to peripheral and central inputs carrying cardiovascular information. Forty-three single units were antidromically activated in the VLM to stimulation of either ipsilateral or contralateral CA with latencies corresponding to conduction velocities of 27.5 +/- 2.0 m/s. Of these 43 units, only 14 (33%) responded orthodromically to stimulation of either the carotid sinus nerve (CSN) or of pressor sites in the paraventricular nucleus of the hypothalamus (PVH) or both. These experiments have demonstrated a bilateral projection of VLM neurons to the CA and have provided evidence for their role in integrating and mediating cardiovascular information from the CSN and PVH directly to spinal sympathetic centers.

Animals↗
PubMed1983

Brainstem projections of aortic baroreceptor afferent fibers in the rat.

Brainstem projections of the aortic nerve in the rat were studied using the transganglionic transport of horseradish peroxidase. Labeled axons were found to project predominantly to the ipsilateral interstitial nucleus and to the ipsilateral dorsolateral aspect of the nucleus of the solitary tract near the level of the obex. Lighter bilateral projections were also found to the medial, ventrolateral and dorsolateral aspects of the solitary complex, and to the commissural nucleus. These data provide evidence of direct aortic baroreceptor afferent projections to restricted regions of the solitary complex and indicate that these specific areas function in the integration of the baroreceptor reflex.

Animals↗
PubMed1983

Direct pathway from cardiovascular neurons in the ventrolateral medulla to the region of the intermediolateral nucleus of the upper thoracic cord: an anatomical and electrophysiological investigation in the cat.

Horseradish peroxidase (HRP) and single unit recording experiments were done in cats to identify neurons in the ventrolateral medulla (VLM) projecting directly to the intermediolateral nucleus (IML) of the thoracic cord and relaying cardiovascular afferent information from the buffer nerves and hypothalamus. In the first series, HRP was allowed to diffuse from a micropipette into the region of the IML at the level of T2. After a survival period of 30-138 h, transverse and horizontal sections of the brainstem were processed according to the tetramethyl benzidine method. Labeled neurons were found in the VLM 1-5 mm rostral to the obex, bilaterally, but with an ipsilateral predominance. The majority were observed in sections 2-4 mm rostral to the obex, clustered in an area lateral to the inferior olivary nucleus around the intramedullary rootlets of the hypoglossal nerve. Additional labeled neurons were found scattered along the ventral surface of the medulla; most of these neurons were oval in shape, 15-30 micron in diameter, and had dendritic processes which lay parallel to the ventral surface. In the second series, the region of the VLM shown to contain labeled neurons was systematically explored for single units antidromically activated by electrical stimulation of the IML in chloralosed, paralyzed and artificially ventilated animals. These antidromically identified units were then tested for their responses to electrical stimulation of the carotid sinus (CSN) and aortic depressor (ADN) nerves, and the paraventricular nucleus (PVH). Ninety-four single units in the VLM were antidromically activated with latencies corresponding to a mean conduction velocity of 19.1 +/- 1.5 m/s. Of these units 52% (49/94) were orthodromically excited by stimulation of buffer nerves; 12 by stimulation of the CSN only (mean latency, 16.0 +/- 3.6 ms), 5 by stimulation of the ADN only (mean latency, 9.5 +/- 2.0 ms), 7 by both buffer nerves, and the remaining 25 units responded to at least one of the buffer nerves and to PVH. Stimulation of PVH excited orthodromically 42 of the 94 units (45%), of which 17 responded only to stimulation of PVH (mean latency, 17.9 +/- 3.5 ms). These experiments provide anatomical and electrophysiological evidence for the existence of a direct cardiovascular pathway from the VLM to the region of the IML and suggest that neurons in the VLM are involved in the integration of cardiovascular afferent inputs from buffer nerves and the hypothalamus to provide an excitatory input to vasoconstrictor neurons in the IML.

Afferent Pathways↗
PubMed1983

Afferent connections to cardiovascular sites in the amygdala: a horseradish peroxidase study in the cat.

To investigate afferent connections to nuclei of the amygdala that have been shown electrophysiologically to receive inputs from baro- and chemoreceptors, small discrete deposits of horseradish peroxidase (HRP) were placed in the region of the central and lateral nuclei of the amygdala in cats. HRP deposits localized to the medial central nucleus of the amygdala labeled neurons in the ipsilateral hypothalamus, primarily in the paraventricular and ventromedial nuclei. In addition, the parabrachial nuclei and the locus coeruleus were observed to project to the region of the central nucleus. After HRP deposits in the medial portion of the lateral nucleus of the amygdala only a few labeled neurons were found scattered throughout the ipsilateral hypothalamus. In addition thalamic and cortical projections shown by previous investigators were confirmed. This study has demonstrated that in the cat several areas in the hypothalamus and brain stem project to the medial portions of the central and lateral nuclei of the amygdala suggesting that these areas may be relay stations for baro- and chemoreceptor information projecting to the amygdala.

Afferent Pathways↗
PubMed1983

Aortic baroreceptor reflex pathway: a functional mapping using [3H]2-deoxyglucose autoradiography in the rat.

The organization of pathways within the central nervous system which are activated by aortic baroreceptor input was studied in the urethane anesthetized rat using the 2-deoxyglucose method. [3H]2-deoxyglucose was administered i.v. while either the aortic nerve was electrically stimulated or aortic baroreceptors were physiologically activated by pulse increases in arterial pressure in animals with bilateral denervation of the carotid sinus. Autoradiographs of transverse sections of the central nervous system were developed and analyzed for changes in metabolic activity in discrete regions compared to control animals, as indicated by the density of the photographic emulsion. Electrical stimulation of the aortic nerve resulted in all animals in an increase in the uptake of deoxyglucose in a number of sites throughout the central nervous system, primarily ipsilateral to the site of stimulation. In the brainstem, structures previously implicated in cardiovascular reflexes were labeled. These included the nucleus of the solitary tract, the solitary tract, the dorsal motor nucleus of the vagus, and the nucleus ambiguus. In addition, the inferior olivary nucleus, the parabrachial nuclei and the ventrolateral reticular formation showed increased labeling. In the hypothalamus, increased labeling was observed only in the paraventricular and supraoptic nuclei.

Afferent Pathways↗