PubMed Health⌕ Search

Biomedical subjects

F R Calaresu

Publications and source records attributed to F R Calaresu.

At least 73 records · Page 4Linked to original sources
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

Units in the amygdala responding to activation of carotid baro- and chemoreceptors.

The distribution of units in the amygdala responding to selective activation of baro- and chemoreceptors was investigated in 12 cats under alpha-chloralose anesthesia. Changes in the firing frequency of spontaneously discharging units were monitored during baroreceptor activation (BA) (phenylephrine hydrochloride, 2 micrograms/kg iv) and chemoreceptor activation (CA) (sodium cyanide, 25 micrograms in 0.1 ml saline into the medial thyroid artery). CA altered the firing frequency of 23% (35/154) of the units; 37% (13/35) were excited, and 63% (22/35) were inhibited. BA altered the firing frequency of 16% (24/154) of the units; 71% (17/24) were excited, while 29% (7/24) were inhibited. The units responsive to CA were located primarily in the dorsomedial amygdala, while those responsive to BA were located primarily in the ventrolateral amygdala. The anatomic separation of units within the amygdala responding to activation of baroreceptors or chemoreceptors suggests that the specificity of function of different parts of the amygdala is related to the different kinds of inputs received by these components of the amygdala from cardiovascular receptors.

Amygdala↗
PubMed1984

Differential control of sympathetic nerve discharge by the brain stem.

This investigation was designed to test the hypothesis that the brain stem differentially controls the basal discharges of postganglionic sympathetic nerves distributed to different organs. Previous studies have shown that the 2- to 6-Hz activity pattern in sympathetic nerves of the baroreceptor-denervated cat originates in the brain stem. In the current study, autocorrelation and power spectral analyses were used to compare the 2- to 6-Hz frequency components of the simultaneously recorded discharges of postganglionic sympathetic nerve pairs (inferior cardiac and renal; external carotid and renal) in baroreceptor-denervated cats anesthetized with sodium diallylbarbiturate and urethan (Dialurethane). In addition, spike-triggered averaging was used to compare the relative strengths of coupling of the basal discharges of single ventrolateral medullary reticular or medullary raphe neurons to activity in postganglionic sympathetic nerve pairs. The major findings of the study are as follows: 1) the predominant 2- to 6-Hz frequency component in the basal discharges of one sympathetic nerve often was different from that in the discharges of a second nerve, and 2) the activity of approximately one-third of ventrolateral medullary reticular neurons and one-half of medullary raphe neurons (with sympathetic-related activity) was differentially related to the discharges of postganglionic nerve pairs. These results support the view that the brain stem reticular formation and raphe complex exert their influences on different sympathetic nerves in a nonuniform fashion.

Animals↗
PubMed1984

Splenic and renal sympathetic responses to stimulation of splenic receptors in cats.

The effect of selective stimulation of splenic receptors on reflex responses of splenic and renal efferent nerves was studied in anesthetized, vagotomized, sinoaortic denervated cats. The following substances were injected into the artery or vein of vascularly isolated spleens: warm physiological saline (congestion), capsaicin (CAPS), bradykinin (BK), and norepinephrine (NE). Splenic congestion increased efferent activity of splenic and renal nerves, splenic venous pressure, systemic arterial pressure, and heart rate. CAPS and BK elicited responses similar to those produced by congestion but caused greater excitation of splenic than renal nerves. Reflex responses were eliminated by section of splenic nerves. Injection of NE increased splenic venous pressure but did not elicit reflex responses. Finally, in contrast to a previous report light- and electron-microscopic examination of splenic nerves revealed myelinated, as well as unmyelinated, fibers. These results have demonstrated that activation of splenic receptors elicits reflex cardiovascular responses and excitation of splenic and renal efferent nerves, contraction of the spleen does not produce reflex responses, the adequate stimulus for reflex responses is stretch of vessels and possibly capsule, and splenic receptors play a role in the reflex control of circulation.

Animals↗
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↗
PubMed1984

Exogenous vasopressin reverses hyperactivity in the hypothalamus of Brattleboro rats.

We have previously described an increase of cytochrome oxidase (COX) activity in discrete hypothalamic nuclei of the Brattleboro rat (BR). The present experiments were done to investigate whether this increase in COX activity could be eliminated by administration of exogenous arginine vasopressin (AVP). Continuous infusion of AVP to BR for 7 days corrected the polyuria and the urine hypoosmolality, as expected, and it also eliminated the COX hyperactivity in the paraventricular nucleus and nucleus circularis of the BR hypothalamus. These results suggest that the hyperactivity of these nuclei in the BR is directly related to their inability to produce AVP.

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

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

Central projections of afferent renal fibers in the rat: an anterograde transport study of horseradish peroxidase.

The projections of afferent renal fibers (ARN) to dorsal root ganglia and into the spinal cord of the rat were studied using the anterograde transport of horseradish peroxidase (HRP). Crystalline HRP was applied to the proximal cut ends of renal nerves or injected as a concentrated solution into the kidney, on either the right or left side. After a survival time of 40-120 h, sections of thoraco-lumbar dorsal root ganglia (DRG) and spinal cord were cut and processed according to the tetramethyl benzidine method. HRP applied either to the ARN or to the kidney on the left labeled neurons in the DRG from T8 to L2. On the other hand, HRP application on the right side resulted in labeling of neurons in DRG T6 to T13. No labeled neurons were found in the contralateral DRG. Labeled neurons in the DRG were of the small (11-20 micron) and medium (30-42 micron) size and were distributed in all portions of the DRG. In the spinal cord the greatest concentration of labeled ARN from the left were found in segments T10-L1, whereas projections from the right ARN were concentrated primarily in segments T7-T10. Labeled fibers entered along the medial aspect of the ipsilateral dorsal horn and projected both rostrally and caudally in the medial portion of Lissauer's tract, sending some collaterals into lamina I. The majority of labeled fibers coursed ventrally along the medial aspect of the dorsal horn towards the midline where they terminated in the region of the dorsal gray commissure, just dorsal to the central canal. Additionally, labeled fibers from the medial projection passed into laminae III-V. No labeled fibers or terminals were observed in the contralateral spinal cord. These data show that ARN enter the spinal cord through several DRG and provide the first anatomical demonstration of central sites of termination of ARN. These spinal sites of projection of sensory information from the kidney are likely to be central sites of integration of reno-renal and visceral reflexes.

Animals↗
PubMed1983

Response of single units in the amygdala to stimulation of buffer nerves in cat.

Electrical activity of spontaneously active units in the amygdala of 19 chloralose-anesthetized cats was monitored for changes in firing frequency during electrical stimulation of the carotid sinus (CSN) and aortic depressor (ADN) nerves. Stimulation of the CSN altered the firing frequency of 30% (73/241) of the units on both sides of the amygdala. Of these units, 47% were excited and 53% were inhibited. Stimulation of the ADN elicited a change in firing frequency of 20% (50/251) of ipsi- and contralateral units. Of these, 68% were excited and the remainder were inhibited. The average latency for all CSN responses (53 +/- 4.0 ms) was significantly longer than the average latency for ADN responses (35 +/- 3.3 ms). The majority of the responsive units were located in the central and lateral nuclei of the amygdala. Spontaneously firing units responding to both CSN and ADN stimulation were found infrequently (7%, 14/188). These results indicate that the two buffer nerves project to specific regions within the amygdala, but the CSN and the ADN follow separate pathways probably involved in reflex arcs mediating different physiological responses.

Amygdala↗
PubMed1983

Parabrachial units responding to stimulation of buffer nerves and forebrain in the cat.

Spontaneously firing units in the region of parabrachial nuclei (PB) and Kölliker-Fuse nuclei (KF) of 19 chloralose-anesthetized cats were monitored for changes in firing frequency during electrical stimulation of carotid sinus (CSN) and aortic depressor (ADN) nerves, of central nucleus of the amygdala (ACE), and of paraventricular nuclei of the hypothalamus (PVH). In the ipsilateral PB 64 of 189 and in the contralateral PB 9 of 103 units responded to CSN stimulation; 18 of 185 ipsilaterally and 7 of 97 contralaterally responded to ADN stimulation. Responses were primarily excitatory, and units were located primarily in the ventrolateral portion of the PB. Only 9 of 267 units responded to stimulation of both CSN and ADN. Stimulation of the ACE and PVH antidromically activated 9 and 7 units, respectively, in PB and approximately half of these also responded to buffer nerve stimulation. In the ipsilateral PB 56 of 207 and in the contralateral PB 11 of 103 units responded orthodromically to ACE stimulation, and 23 of 177 ipsilaterally and 2 of 103 contralaterally responded orthodromically to PVH stimulation with primarily excitatory responses and were located primarily in the ventrolateral portion of the PB and KF. Of these units approximately half also responded to buffer nerve stimulation. These results suggest an important role for PB-KF in mediating ascending and descending cardiovascular and respiratory control signals.

Afferent Pathways↗
PubMed1982

Medullary origin of vagal preganglionic axons to the heart of the cat.

It is apparent from the literature that a controversy exists concerning the site of origin of cardiac vagal preganglionic axons. Physiological studies have suggested that the location of these neurons may be different in different species and there has been disagreement between physiological and anatomical findings in the same species. We now present anatomical and neurophysiological studies suggesting that in the cat cardiac vagal preganglionic neurons are located in two medullary regions: the areas of the dorsal motor nucleus of the vagus (DMV) and of the nucleus ambiguus (AMB). This suggestion is based on the following observations. Firstly, after application of horseradish peroxidase to the right cardiac branches of the vagus nerve, labeled neurons were found primarily in the regions of te DMV and AMB. Additional scattered neurons were found in the reticular formation between these two nuclei. Secondly, following injections of tritiated amino acids into either the DMV or AMB, labeled vagal fibers were found in the atrial myocardium. Finally, electrical stimulation of the right cardiac branches of the vagus nerve antidromically activated DMV or AMB, labeled vagal fibers were found in the atrial myocardium. Finally, neurons in the DMV and AMB regions with latencies corresponding to conduction velocities of B-fibers. In addition, these neurons were orthodromically excited by electrical stimulation of the carotid sinus and aortic depressor nerves.

Animals↗
PubMed1981

Glossopharyngeal and vagal afferent projections to the brain stem of the cat: a horseradish peroxidase study.

Brain stem projections of the glossopharyngeal and vagus nerves in the cat were studied using the anterograde transport of horseradish peroxidase (HRP). Crystalline HRP was applied to the proximal cut ends of the nerves for a period of 4-10.5 h, and after a survival time of 24-120 h, transverse and horizontal sections of the brain stem were processed according to the tetramethylbenzidine method. Labeled fibers from both nerves were found to project bilaterally to the solitary complex, and ipsilaterally to the ventral region of the external cuneate nucleus and to the medial region of the nucleus praepositus hypoglossi, just dorsolateral to the medial longitudinal fasciculus. Within the solitary complex terminal labeling was found in the parvocellular, ventrolateral, lateral, medial and commissural solitary nuclei. Exclusive glossopharyngeal nerve projections were found ipsilaterally in the rostral dorsal motor nucleus of the vagus, the ventrolateral portion of the medial cuneate nucleus, the dorsal part of the nuclei caudalis and interpolaris of the trigeminal complex, the nuclei insulae cuneati lateralis, and the dorsolateral aspect of the nucleus medullae oblongata centralis. Finally, in the area postrema a bilateral projection of vagal and an ipsilateral projection of glossopharyngeal fibers were found. These findings demonstrate that the glossopharyngeal nerve has more widely distributed brain stem projections that the vagus nerve and provide essential information on projection sites of visceral and taste inputs to the central nervous system.

Afferent Pathways↗
PubMed1981

Projections from buffer nerves to the nucleus of the solitary tract: an anatomical and electrophysiological study in the cat.

The projections of aorta depressor (ADN) and carotid sinus (CSN) afferent fibers to the region of the nucleus of the solitary tract were studied in the cat with the anterograde transport of horseradish peroxidase (HRP) technique and by recording single unit activity during electrical stimulation of these nerves. In the first series of experiments, after application of crystalline HRP to the proximal cut end of either buffer nerve and a postoperative survival period of 24-120 h, brain stem sections were processed according to the tetramethyl benzidine method. ADN and CSN labeling were found bilaterally, with a predominant ipsilateral labeling, in the medial (Sm), lateral (Slt), commissural (Com) and dorsomedial aspect of the parvocellular solitary nuclei. Additional CSN labeling was found in the ventrolateral and intermediate (Int) solitary nuclei, in the reticular formation ventrolateral to the solitary complex and along the dorsal border of the dorsal motor nucleus of the vagus. In the second series of experiments these areas receiving primary afferent fibers were explored for single units responding to stimulation for the buffer nerves in chloralosed cats, paralyzed and artificially ventilated. Of 177 responsive units, 80 responded only to stimulation of the CSN, 44 only to the ADN and 53 to both nerves. Responsive units were found throughout the rostrocaudal extent of the solitary complex and areas adjacent to the solitary complex. However, most of the units were found in 3 regions: the Sm, Slt and adjacent areas. Units in the Slt and Com were found to respond to only one input, either the CSN or the ADN alone. On the other hand, units in the Int responded only to both buffer nerves and not selectively to one nerve. These results demonstrate that the CSN has a wider distribution in the solitary complex than the ADN and that second order neurons in the solitary complex receive inputs from either one or both buffer nerves, suggesting a degree of separation of central pathways carrying cardiovascular afferent information.

Afferent Pathways↗