Biomedical subjects

T Petrov

Publications and source records attributed to T Petrov.

At least 19 recordsLinked to original sources

PubMed2007

Lamins of ocular lens epithelial cells.

Experiments were performed to characterize a prominent nuclear matrix (NM) protein isolated from tissue cultured mouse lens epithelial cells. This NM protein was separated by SDS-PAGE and the stained gel band was analyzed by mass spectroscopy. Blast analysis of the amino acid sequence derived by mass spectroscopy revealed the presence of Lamin C in the NM of the mouse lens epithelial cells. We also examined nuclear proteins of adult and fetal human lenses. Data collected from these experiments showed the presence of Lamin C in both adult and fetal lens cells. However fetal lens cells only show Lamin C dimers, whereas adult human lens contained dimers, monomers and degraded Lamin C. Early and late passaged tissue cultured mouse lens epithelial cells also contained Lamin C in the nucleus with a preponderance of the dimer in the early passaged cells. The biological significance of the presence of dimers in human fetal lens cells and early passaged mouse lens cells is not known. However, it could suggest an enhanced docking capability of Lamin C dimers for other physiologically important nuclear proteins.

Adult↗

PubMed2004

Intracellular coexpression of endothelin-1 and inducible nitric oxide synthase underlies hypoperfusion after traumatic brain injury in the rat.

We used Marmarou's rat model of traumatic brain injury to demonstrate colocalization of mRNAs for endothelin-1 (ET-1, a powerful vasoconstrictor) and inducible nitric oxide synthase (iNOS, generator of NO, a vasodilator) in individual cells that form the brain's microvascular wall. The results were confirmed with double immunocytochemistry. After trauma endothelial, smooth muscle cells and macrophages contributed to the abnormal synthesis of ET-1 and iNOS which may underlie a dysfunctional brain microcirculation. This is the first in vivo single cell demonstration of ET-1 and iNOS colocalization, suggesting reciprocal regulation of each other's expression both at the transcriptional and translational levels. The results further indicate that interaction between ET-1 and iNOS occurs at the cytosol and possibly the nuclear membranes, implicating mediation via endothelin receptors.

Animals↗

PubMed2004

Differences in cell activation by Chlamydophila pneumoniae and Chlamydia trachomatis infection in human endothelial cells.

Seroepidemiological studies and demonstration of viable bacteria in atherosclerotic plaques have linked Chlamydophila pneumoniae infection to the development of chronic vascular lesions and coronary heart disease. In this study, we characterized C. pneumoniae-mediated effects on human endothelial cells and demonstrated enhanced phosphorylation and activation of the endothelial mitogen-activated protein kinase (MAPK) family members extracellular receptor kinase (ERK1/2), p38-MAPK, and c-Jun-NH2 kinase (JNK). Subsequent interleukin-8 (IL-8) expression was dependent on p38-MAPK and ERK1/2 activation as demonstrated by preincubation of endothelial cells with specific inhibitors for the p38-MAPK (SB202190) or ERK (U0126) pathway. Inhibition of either MAPK had almost no effect on intercellular cell adhesion molecule 1 (ICAM-1) expression. While Chlamydia trachomatis was also able to infect endothelial cells, it did not induce the expression of endothelial IL-8 or ICAM-1. These effects were specific for a direct stimulation with viable C. pneumoniae and independent of paracrine release of endothelial cell-derived mediators like platelet-activating factor, NO, prostaglandins, or leukotrienes. Thus, C. pneumoniae triggers an early signal transduction cascade in target cells that could lead to endothelial cell activation, inflammation, and thrombosis, which in turn may result in or promote atherosclerosis.

Chlamydia trachomatis↗

PubMed2001

Peripheral target contact regulates Ca2+ channels in the cell bodies of bullfrog sympathetic ganglion B-neurons.

Tyrosine-hydroxylase immunohistochemistry demonstrated that a single injection of 120 mg/kg 6-hydroxydopamine (6-OHDA) reversibly disconnected bullfrog sympathetic ganglia from their peripheral targets. This was correlated with a decrease in sympathetic outflow to the eyes and a reversible decrease in pupil diameter. 6-OHDA did not damage the cell bodies of ganglionic neurons. Calcium channel current in ganglionic B-neurons, (measured at -10 mV; holding potential -60 mnV; Ba2+ as charge carrier; IBa) was reduced. It reached a minimum of about 40% of control amplitude 7-14 days after 6-OHDA injection and recovered to 73% of control amplitude after 63 days. 6-OHDA induced loss and recovery of functional sympathetic innervation of peripheral target tissues, as determined by measurement of pupil diameter, occurred at a similar rate. Thus, pupil diameter attained mininum values 7-14 days after 6-OHDA treatment and recovered to 81% of control after 63 days. The properties of Ca2+ channels in sympathetic neurons are, therefore, determined by continuity of contact with peripheral target. 6-OHDA also decreased the peak amplitude and duration of the afterhyperpolarization (a.h.p) that follows the action potential (a.p.). The rate of recovery of a.h.p duration was more rapid than the rate of recovery of peak a.h.p. amplitude. This may reflect known differences in properties of two types of Ca2+-sensitive K currents. IC and IAHP, IC, which is responsible for the peak amplitude of the a.h.p has a low affinity for Ca2+, whereas IAHP, which determines a.h.p. duration, has higher Ca2+ affinity.

Action Potentials↗

PubMed2001

Upregulation of iNOS expression and phosphorylation of eIF-2alpha are paralleled by suppression of protein synthesis in rat hypothalamus in a closed head trauma model.

When the inducible form of nitric oxide synthase (iNOS) is expressed after challenge to the nervous system, it results in abnormally high concentrations of nitric oxide (NO). Under such conditions, NO could phosphorylate the eukaryotic translation initiation factor (eIF)-2alpha, thus suppressing protein synthesis in neurons that play a role in endocrine and autonomic functions. Using the Marmarou model of traumatic brain injury (TBI), we observed a rapid increase (at 4 h after TBI) of iNOS mRNA in magno- and parvocellular supraoptic and paraventricular neurons, declining gradually by approximately 30% at 24 h and by approximately 80% at 48 h. Western analysis indicated a trend towards increased iNOS protein synthesis at 4 h, which peaked at 8 h, and tended to decrease at the later time points. At the same time points, we detected immunocytochemically the phosphorylated form of eIF-2alpha (eIF-2alpha[P]) as cytoplasmic and more often as nuclear labeling. The incidence of double-labeled [iNOS and eIF-2alpha(P)] neuronal profiles, particularly at 24 h and 48 h after TBI, was high. De novo protein synthesis assessed quantitatively after infusion of 35S methionine/cysteine was reduced by approximately 20% at 4 h, remained depressed at 24 h, and did not return to control levels up to 48 h following the trauma. The results suggest that iNOS may trigger phosphorylation of eIF-2alpha, which in turn interferes with protein synthesis at the translational (ribosomal complex) and transcriptional (chromatin) levels. The depression in protein synthesis may include downregulation of iNOS itself, which could be an autoregulatory inhibitory feedback mechanism for NO synthesis. Excessive amounts of NO may also participate in dysfunction of hypothalamic circuits that underlie endocrine and autonomic alterations following TBI.

Animals↗

PubMed2000

Lithium treatment in ovo: effects on embryonic heart rate, natural death of ciliary ganglion neurons, and brain expression of a highly conserved chicken homolog of human MTG8/ETO.

Understanding the action of the mood stabilizer lithium is dependent on availability of experimental models where lithium treatment at clinically relevant concentrations induces marked phenotypic and genotypic changes. Here we report on such changes in the chicken embryo. Lithium chloride (0.6 mM), applied in ovo 60 h after incubation, markedly delayed the heart rate increase observed from ED2.5 to ED5, and induced the brain expression of a new chicken gene cETO from ED7 to ED15. At the same time the overall developmental dynamics and embryo survival, or the expression of chicken gephyrin were not significantly affected. Furthermore, lithium treatment (0.3 mM, 48 h after incubation) abolished the difference in neuronal number between ED12 ciliary ganglia developing in the presence or absence of postganglionic target muscles. We show that cETO is a close homologue of the human transcription factor MTG8/ETO; named after its location on chromosome 8, and participation in chromosomal translocation 8;21 in myeloid leukemia. The mRNA and protein levels of ETO and gephyrin had a parallel course in chicken brain development suggesting that the expression of both genes is regulated mainly at the level of gene transcription. However, the patterns of expression were markedly different. ETO peaked at ED7 and decreased five-fold at ED15. In contrast, gephyrin levels increased five-fold from ED7 to ED15. We propose that the induction of ETO expression, in concert with lithium-induced upregulation of other genes, such as PEBP2beta and bcl-2, is participating in the neuroprotective effect of chronic lithium treatment.

Amino Acid Sequence↗

PubMed2000

Expression of the inducible nitric oxide synthase in distinct cellular types after traumatic brain injury: an in situ hybridization and immunocytochemical study.

The Marmarou's acceleration traumatic brain injury (TBI) model, in situ hybridization and immunocytochemistry were utilized to study the temporal expression of the inducible form of nitric oxide synthase (iNOS) mRNA and protein in different cellular compartments of the rat brain. Four hours following TBI, expression of iNOS was observed in the endothelial cells of cerebral blood vessels, macrophages and many cortical and hippocampal neurons. In the cortex labeled neuronal and nonneuronal cells were primarily found in the superficial layers. In the hippocampus the strongest neuronal labeling was observed in the CAI and CA3 (lateral part) regions. By 24 h post TBI endothelial cells no longer expressed iNOS mRNA, and the macrophage and neuronal iNOS expression was reduced by 30-50%. The reduction was assessed by automated quantitation of the silver grains that occupy individual cellular profiles using an image analysis system. Immunocytochemistry revealed de novo iNOS synthesis in non-neuronal cells at the different time points, thus paralleling the changes in iNOS mRNA expression. In contrast, iNOS immunoreactivity in neurons was not observed before 24 h post TBI, suggesting failure of iNOS protein translation at 4 h after trauma. The results demonstrate complex spatial and temporal patterns of iNOS expression in discrete cellular populations, indicating different times of nitric oxide synthesis (and release) following TBI. Uncoupling of iNOS mRNA and protein synthesis in neurons suggests differential synthesis of nitric oxide in these cells as compared to non-neuronal cellular populations after trauma.

Animals↗

PubMed1999

Effects of inhibitory neurotransmitters on the mudpuppy (Necturus maculatus) locomotor pattern in vitro.

Effects of inhibitory neurotransmitters on the locomotor rhythm and pattern generation were investigated using an in vitro preparation isolated from the mudpuppy (Necturus maculatus). The preparation consisted of the first five segments of the spinal cord and the right forelimb attached by the brachial nerves. During N-methyl-d-aspartate (NMDA)-induced locomotion, the rhythmic motor output (EMG) was recorded unilaterally from elbow flexor and extensor muscles. While neither glycine nor gamma-aminobutyric acid (GABA)-related substances induced locomotion in the absence of NMDA, they modulated NMDA-induced locomotion. Bath application of glycine and GABA suppressed the rhythmic motor pattern induced by NMDA. Addition of glycine receptor antagonist strychnine or GABA(A) receptor antagonist bicuculline disrupted the phase relationship between antagonistic motor pools during ongoing locomotion, thereby changing the normal alternating pattern into synchronous EMG bursts. Both the GABA(A) receptor agonist muscimol and GABA(B) receptor agonist baclofen mimicked the effects of GABA as they either slowed down or stopped locomotion. Nipecotic acid, a GABA uptake blocker, had a similar effect. This suggested that an endogenous release of GABA modulated the locomotor rhythm. The endogenous release was antagonized by the GABA(A) and GABA(B) receptor antagonists bicuculline and CGP-35348, respectively. Immunocytochemistry revealed that glycine and GABA-positive neurons and fibers were present in mudpuppy spinal cord. Although the GABAergic neurons were more numerous than glycinergic neurons, both cell types contributed processes directed towards the white matter and occasionally towards the ependymal lining of the central canal. Our results suggest that inhibitory neurotransmitters exert powerful actions upon the neuronal network governing forelimb locomotion in the mudpuppy. The effects we observed may be mediated by a network of segmentally distributed glycinergic and GABAergic spinal neurons.

Animals↗

PubMed1998

Activation of neuropeptide FF neurons in the brainstem nucleus tractus solitarius following cardiovascular challenge and opiate withdrawal.

Neuropeptide FF (NPFF), a morphine modulatory peptide, is localized within discrete autonomic regions including the brainstem nucleus tractus solitarius (NTS) and the parabrachial nucleus (PBN). We investigated the activation of NPFF neurons in the NTS of rats induced by cardiovascular challenge and centrally generated opiate withdrawal. For hypotensive stimulation, we used systemic infusions of sodium nitroprusside (NP) or hemorrhage (HEM), and hypertension was achieved by intravenous phenylephrine (PHENYL) or angiotensin II (AII). In rats that received continuous intracerebroventricular injections of morphine, intraperitoneal injections of naloxone precipitated behavioural signs of opioid withdrawal. Activated NTS neurons were identified by using a combined immunohistochemistry for Fos and NPFF, and neurons projecting to the PBN were determined with a retrograde tracer. HEM, administration of vasoactive drugs, and opiate withdrawal produced a very robust activation of NTS neurons. In NP and HEM groups, 25.6+/-3.2% and 7.6+/-1.3% of NPFF neurons were activated, respectively. Lesser numbers of NPFF neurons were activated in the PHENYL (4.6+/-1.6%) and AII (2.4+/-0.8%) groups. However, following opiate withdrawal, virtually no Fos expression was observed in NPFF neurons. NPFF neurons activated during NP infusion constituted the largest number of cells projecting to the PBN. This study shows that NPFF neurons in NTS that project to the PBN respond selectively to NP as opposed to other cardiovascular challenges or opiate withdrawal. These data support an emerging and important role for NPFF in the context of central cardiovascular regulation.

Angiotensin II↗

PubMed1997

The expression of the low affinity nerve growth factor receptor in long-term denervated Schwann cells.

Schwann cells in the distal stump of injured peripheral nerves synthesize the low affinity nerve growth factor receptor (p75). In this study we used short-term (1 week) and long-term (1-12 months) transected distal sciatic nerves of rats to determine the variations of p75 expression by using immunocytochemistry and in situ hybridization. Semi-quantitative analysis revealed that the synthesis of the protein product of the p75 gene is rapidly enhanced to reach a peak within the 1 month after denervation. After that it gradually decreased and was barely detectable 6 months following denervation. Double immunocytochemistry for p75 and the S100 protein revealed that p75 immunoreactivity is confined to the Schwann cells. Quantitative analysis of our in situ hybridization experiments revealed that the upregulation of the p75 mRNA parallels the enhanced synthesis of the corresponding protein and reaches a peak within 1 month, which is maintained until the second month after the transection and declines thereafter to reach background levels at 4 months. The electron microscopic observations reveal that the increase in the number of nuclei in the distal stump belong to severely atrophied Schwann cells and fibroblasts. Since the presence of p75 in the Schwann cells is necessary for reinnervation, our results indicate that, based on the expression of p75, the Schwann cells will provide a most suitable environment for the regenerating axons up to the first month. At later stages the ability of the Schwann cells to synthesize p75 and cell adhesion proteins such as N-CAM and GAP 43 decreases which may be one of the factors that contribute to poor functional recovery if the regenerating axons reach the distal stump after long periods of time.

Animals↗

PubMed1997

An electrophysiological study of neurons in the horizontal limb of the diagonal band of Broca.

We examined the morphological and electrophysiological properties of neurons within the horizontal limb of the diagonal band of Broca (hDBB) and investigated the role of excitatory amino acid mediated synaptic transmission in this region. Whole cell patch-clamp recordings were obtained from hDBB neurons in rat forebrain slices. The hDBB cells examined in this study display a morphological and electrophysiological profile that is consistent with the type B, noncholinergic cell type. Cable analysis reveals that hDBB neurons are electrotonically compact and may therefore function as efficient relays for transmission of inputs to other forebrain target sites. Application of agonists for alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA), kainate, N-methyl-D-aspartate (NMDA), and metabotropic receptors all evoke inward currents in hDBB neurons. Pharmacological analyses of synaptic events indicate that evoked excitatory postsynaptic currents (EPSC) are either mediated by non-NMDA receptors alone or a combination of non-NMDA and NMDA receptors. In some neurons, the metabotropic receptor agonist, 1-aminocyclopentane-trans-1, 3-dicarboxylic acid, reduced EPSC amplitude without altering postsynaptic input conductance, thus suggesting a presynaptic locus of action. The electrical and pharmacological properties described for hDBB neurons may be physiologically relevant for the effective transmission of excitatory synaptic inputs to sites that receive projections from the hDBB.

Animals↗

PubMed1996

Activation of nitric oxide-synthesizing neurones during precipitated morphine withdrawal.

Activation of nitric oxide (NO)-synthesizing neurones in the hypothalamus and brain stem was studied during naloxone-precipitated morphine withdrawal in rats. In animals that underwent behavioural changes consistent with withdrawal, Fos and nicotinamide dinucleotide phosphate-diaphorase (NADPH-D)-positive neurones were identified within the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei as well as the brain stem nucleus tractus solitarius (NTS). A larger proportion of NADPH-D-positive neurones were activated in the PVN than in the NTS. While NO has been implicated in the genesis of opioid withdrawal, the present data provide evidence for the activation of select populations of NO-synthesizing neurones during the opiate withdrawal syndrome.

Animals↗

PubMed1996

Serotonergic modulation of the mudpuppy (Necturus maculatus) locomotor pattern in vitro.

The aims of the present study were to: (1) study the role of serotonin (5-HT) in modulating the central pattern generator (CPG) underlying locomotion in the mudpuppy (Necturus maculatus); (2) investigate whether there is an intrinsic spinal serotonergic system. These aims were achieved by the use of pharmacological and immunocytochemical methods. To study modulation of the locomotor pattern and rhythm, we applied 5-HT, its uptake blocker zimelidine, and a variety of 5-HT receptor agonists and antagonists to an in vitro brainstem-spinal cord preparation isolated from the mudpuppy. The preparation consisted of the first five segments of the spinal cord and the right forelimb attached by the brachial plexus. The spinal CPG for locomotion was activated chemically by adding NMDA to the superfusing solution. During locomotion, bipolar electromyographic (EMG) recordings were made unilaterally from flexor and extensor ulnae muscles. 5-HT on its own did not induce locomotion, but it did have a profound modulatory effect on NMDA-induced locomotion. 5-HT produced a dose-dependent increase in the overall cycle duration and enhanced the EMG burst duration. Use of zimelidine indicated that there is an endogenous release of 5-HT which modulated the locomotor rhythm. The endogenous release was antagonized by 5-HT1/5-HT2 receptor antagonist methiothepin. Immunocytochemical analysis, in which the entire spinal cord of the mudpuppy was used, revealed that there were more than one type of spinal serotonergic neuron. They were differentiated according to the cell diameter, shape, and arborization pattern of their processes. These neurons were located within the central gray matter ventrolateral to the central canal. Our results suggest that 5-HT plays an important role in modulating the locomotor CPG in the mudpuppy, by acting through a well-developed spinal serotonergic system. This is in contrast to what has been reported in higher vertebrates, where serotonergic innervation is derived from supraspinal structures.

Animals↗

PubMed1996

Connectivity between brainstem autonomic structures and expression of c-fos following electrical stimulation of the central nucleus of the amygdala in rat.

Combinations of retrograde tracing with detection of Fos (the protein product of the immediate early gene c-fos) following electrical stimulation of the central nucleus of the amygdala were used to explore: (1) the connectivity of activated (Fos-positive) neurons in the ventrolateral medulla with the nucleus of the solitary tract; (2) the connectivity of activated neurons in the nucleus of the solitary tract with the ventrolateral medulla; (3) the proportion of activated catecholaminergic neurons that project to the nucleus of the solitary tract or to the ventrolateral medulla. Retrograde tracer was injected into the nucleus of the solitary tract or the ventrolateral medulla. After 5 days, stimulation for 60 min induced a statistically significant increase in the number of Fos-immunoreactive neurons in the ventrolateral medulla that project to the nucleus of the solitary tract and in the number of Fos-positive neurons in the nucleus of the solitary tract that project to the ventrolateral medulla. Of the neurons activated by stimulation of the central nucleus of the amygdala, 20% in the ventrolateral medulla and 3% in the nucleus of the solitary tract contained the retrograde tracer and were also immunopositive for tyrosine hydroxylase, the enzyme responsible for synthesis of catecholamines.

Adrenal Medulla↗

PubMed1996

Parabrachial nucleus projection to the amygdala in the rat: electrophysiological and anatomical observations.

The amygdala, an important limbic forebrain centre, is the recipient of projections from a number of autonomic brainstem nuclei including the pontine parabrachial nucleus. This study examined the influence of electrical stimulation of the parabrachial nucleus on the excitability of amygdala neurons and their response to two cardiovascular stimuli, namely baroreceptor activation and the administration of systemic angiotensin II. We also defined the chemical identity of some amygdala neurons that receive parabrachial nucleus projections by combining the transport of the anterograde tracer Phaseolus vulgaris leucoagglutinin injected into the parabrachial nucleus with immunocytochemical labelling of neurotensin and galanin profiles within the amygdala. In urethane-anesthetized rats, stimulation of parabrachial nucleus evoked four basic types of synaptic responses in amygdala cells: (1) a short duration (< 100 ms) excitation in 75 of 167 neurons, (2) a longer duration (> 100 ms) excitatory response in 36 neurons, (3) an inhibitory response in 32 cells, and (4) more complex responses consisting of excitation-inhibition or inhibition-excitation sequences in the remainder of the cells. Thirty-seven of 72 amygdala neurons activated synaptically by parabrachial nucleus stimulation also responded to baroreceptor activation or intravenous angiotensin II. Anatomical data revealed the presence of Phaseolus vulgaris leucoagglutinin labelled terminals predominantly within the lateral, medial, and capsular subdivisions of the central nucleus of amygdala. Phaseolus vulgaris leucoagglutinin varicosities and boutons were observed apposed to the neurotensin and galanin neuronal perikarya within the central nucleus of amygdala. The electrophysiological results provide a framework whereby parabrachial nucleus efferents influence the activity of amygdala neurons that are responsive to cardiovascular stimuli. Furthermore, the anatomical data indicate that a portion of the parabrachial nucleus input is directed toward galanin and neurotensin neurons within the central nucleus of amygdala.

Amygdala↗

PubMed1995

Convergent influence of the central nucleus of the amygdala and the paraventricular hypothalamic nucleus upon brainstem autonomic neurons as revealed by c-fos expression and anatomical tracing.

Combinations of anatomical tracing with detection of Fos (the protein product of the immediate early gene c-fos) consequent to the stimulation of the central nucleus of the amygdala were used to explore the possibility that the hypothalamic paraventricular nucleus participates in the activation of brainstem neurons in the nucleus of the solitary tract and ventrolateral medulla. After injections of the anterograde tracer Phaseolus vulgaris leucoagglutinin in the paraventricular nucleus, labeled fibers and varicosities were found to impinge on catecholaminergic and non-catecholaminergic Fos-positive neurons in the brainstem. After injections of a retrograde tracer in the nucleus of the solitary tract or ventrolateral medulla, we observed that some of the Fos-positive neurons within the parvocellular paraventricular nucleus that project to the brainstem were catecholaminergic or oxytocinergic. The results indicate that direct and indirect inputs from the amygdala may influence the activity of autonomic neurons in the brainstem. The paraventricular nucleus, via its direct projections onto catecholaminergic and non-catecholaminergic neurons, may participate in activation of brainstem neurons. Activated catecholaminergic and oxytocinergic parvocellular neurons in the paraventricular nucleus may be involved in the transmission of autonomic signals from the amygdala toward the brainstem.

Amygdala↗

PubMed1995

Hypotension induces Fos immunoreactivity in NADPH-diaphorase positive neurons in the paraventricular and supraoptic hypothalamic nuclei of the rat.

Double staining for Fos and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-D) was used to study the distribution of activated neurons that synthesize nitric oxide in the paraventricular (PVN) and supraoptic nuclei (SON) following hypotensive stimulation in conscious rats. Fos was detected in many magno- and parvocellular NADPH-D positive neurons in response to haemorrhage or drug-evoked hypotension using i.v. infusions of sodium nitroprusside. However, quantitative analysis did not reveal any differences in the number of Fos positive PVN neurons following either mode of stimulation. These results suggest that a subpopulation of hypothalamic NADPH-D positive neurons is activated following hypotensive challenge. This activation of NADPH-D neurons may occur indirectly through other CNS structures that influence the excitability of hypothalamic SON and PVN. Furthermore, the lack of a difference in activated neurons within the PVN following either haemorrhage or nitroprusside infusion suggests that while a drop in blood pressure causes activation of neurons that produce nitric oxide, a decrease in blood volume, which accompanies haemorrhage, does not.

Animals↗

PubMed1994

Chemically defined collateral projections from the pons to the central nucleus of the amygdala and hypothalamic paraventricular nucleus in the rat.

Triple fluorescence labelling was employed to reveal the distribution of chemically identified neurons within the pontine laterodorsal tegmental nucleus and dorsal raphe nucleus which supply branching collateral input to the central nucleus of the amygdala and hypothalamic paraventricular nucleus. The chemical identity of neurons in the laterodorsal tegmental nucleus was revealed by immunocytochemical detection of choline-acetyltransferase or substance P; in the dorsal raphe nucleus, the chemical content of the neurons was revealed with antibody recognizing serotonin. The projections were defined by injections of two retrograde tracers, rhodamine- and fluorescein-labelled latex microspheres, in the central nucleus of the amygdala and paraventricular nucleus, respectively. Neurons projecting to both the central nucleus of the amygdala and the paraventricular nucleus were distributed primarily within the caudal extensions of the laterodorsal tegmental nucleus and dorsal raphe nucleus. Approximately 11% and 7% of the labelled cells in the laterodorsal tegmental nucleus and dorsal raphe nucleus projected via branching collaterals to the paraventricular nucleus and central nucleus of the amygdala. About half of these neurons in the laterodorsal tegmental nucleus were cholinergic, and one-third were substance-P-ergic; in the dorsal raphe nucleus, approximately half of the neurons containing both retrograde tracers were serotonergic. These results indicate that pontine neurons may simultaneously transmit signals to the central nucleus of the amygdala and paraventricular nucleus and that several different neuroactive substances are found in the neurons participating in these pathways. This coordinated signalling may lead to synchronized responses of the central nucleus of the amygdala and paraventricular nucleus for the maintenance of homeostasis.(ABSTRACT TRUNCATED AT 250 WORDS)

Amygdala↗