SEARCH · PubMed Health

Results for “Dihydroxytryptamines”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources

PubMed1981

Noradrenergic innervation of serotonergic neurons in the dorsal raphe: demonstration by electron microscopic autoradiography.

In this study, noradrenergic (NE) terminals in the dorsal raphe were identified by [3H]NE electron microscopic (EM) autoradiography. Lesioning of NE terminals by treatment with the selective catecholamine neurotoxin, 6-hydroxydopamine produced a marked decrease in NE-labelled terminals. [3H]5-HT EM autoradiography of the dorsal raphe produced labelling of cell bodies, dendrites and axons but labelled terminals with synaptic junctions were not observed. Serotonergic (5-HT) neurons were identified at an early stage of degeneration following treatment with the selective 5-HT neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT). When both [3H]NE autoradiography and 5,7-DHT lesioning were combined, a majority of NE-labelled terminals, which formed synaptic specializations, innervated degenerating dendrites. These findings suggest that NE terminals directly innervate 5-HT cells in the dorsal raphe.

5,7-Dihydroxytryptamine↗

PubMed1981

Experimentally induced supersensitivity of neocortical neurons to microiontophoretically administered serotonin.

Central serotonergic fiber systems of the rat were selectively lesioned by intraventricular injection of the neurotoxin 5,7-dihydroxytryptamine (5,7-DHT). At various times thereafter, the sensitivity of rostral cortical neurons to microiontophoretically administered serotonin (5-HT) was compared in groups of lesioned and sham-operated animals pretreated with the 5-HT uptake inhibitor CGP 6085. Twenty-four hours after the injection of 5,7-DHT, at which time the cortical 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) levels were both reduced by 40%, there was no significant difference in the sensitivity of cortical neurons to 5-HT. However, 3 days after such treatment, when the cortical 5-HT and 5-HIAA levels were reduced by 52% and 53% respectively, pronounced supersensitivity to 5-HT was noted. The depressant action of 5-HT on neuronal firing was potentiated with regard to both maximal firing depression and duration of the firing inhibition. A similar potentiation of the 5-HT responses was observed 7 days after lesioning. Supersensitivity thus appears to develop between 1 and 3 days after the injection of 5,7-DHT. Seven days after lesioning, the sensitivity of rostral cortical neurons to gamma-aminobutyric acid was unchanged compared to that observed in sham-operated animals.

5,7-Dihydroxytryptamine↗

PubMed1981

Raphe pallidus and raphe obscurus projections to the intermediolateral cell column in the rat.

The descending spinal projections from the raphe pallidus and raphe obscurus nuclei were studied by the anterograde autoradiographic technique in the rat. Both regions project to the intermediolateral cell columns. These pathways were destroyed by intraventricular injections of 5,7-dihydroxytryptamine, a neurotoxin relatively specific for serotonergic cells.

5,7-Dihydroxytryptamine↗

PubMed1981

Differential pulse voltammetry in brain tissue. I. Detection of 5-hydroxyindoles in the rat striatum.

In vitro, differential pulse voltammetry combined with electrochemically treated carbon fiber electrodes enabled detection, in different solution of 5-hydroxyindole compounds, of an oxidation peak 3 at +300 mV. In vivo, a striatal peak 3 was also recorded at this potential. Electrolytic or 5,7-dihydroxytryptamine lesions interrupting the medial forebrain bundle (MFB) were followed by a decrease of 65% and 64% in peak height, but not elimination of the peak. Biochemical determinations were significantly correlated to the peak 3 measurements. The existence of peak 3 as well as hydroxyindole compounds in blood suggested a blood contamination under the experimental conditions employed. This possibility is confirmed both by the complete disappearance of striatal peak 3 in animals with the MFB lesioned and surgically prepared a week before recordings, and by biochemical measurements in parachlorophenylalanine-treated or perfused (phosphate-buffered saline solution) animals.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1982

Somatostatin-like immunoreactive material in the rabbit retina.

Somatostatin-like immunoreactivity was detected by a specific radioimmunoassay in extracts of retinas of Dutch-belted rabbits at a mean concentration of 1.1 +/- 0.1 ng/retina, or 170 +/- 30 pg/mg protein. On both gel permeation chromatography and reversed phase high performance liquid chromatography, the majority of this material was indistinguishable from somatostatin-14; a smaller amount of immunoreactive material co-chromatographed with somatostatin-28. The somatostatin-like immunoreactivity was concentrated in a P2 (synaptosomal) fraction prepared by differential centrifugation. The concentration of somatostatin-like immunoreactivity was unaffected by the prior intravitreal injection of the selective neurotoxins 6-hydroxydopamine and 5, 7-dihydroxytryptamine. The rabbit retina, therefore, contains readily detectable amounts of material chemically similar to somatostatin-14 and somatostatin-28. This material is concentrated in neurosecretory elements of the retina, but is not contained in cells which accumulate dopamine or indoleamines. The rabbit retina is suitable for in vitro studies of the central nervous system function of the somatostatin family of peptides.

5,7-Dihydroxytryptamine↗

PubMed1982

Evidence that serotonergic neurons in the dorsal raphe nucleus exert a stimulatory effect on the secretion of renin but not of corticosterone.

Data from previous experiments in rats indicate that release of serotonin in the central nervous system increases renin and corticosterone secretion. To determine which serotonergic neurons are involved, lesions of the dorsal or median raphe nuclei were produced by local injections of 5,7-dihydroxytryptamine (5,7-DHT) in rats, and 2 weeks later, the renin responses to parachloroamphetamine (PCA) were determined. Plasma corticosterone was also measured. PCA produced significant increases in plasma renin activity and plasma corticosterone in sham-lesioned animals and animals with median raphe lesions. The plasma corticosterone response to PCA was also normal in rats with dorsal raphe lesions but the renin response was significantly reduced. The data support the hypothesis that serotonergic neurons in the dorsal raphe nucleus are part of a neural pathway mediating increased renin secretion, and that the stimulatory effect of serotonin on corticosterone secretion is mediated by a different pathway.

5,7-Dihydroxytryptamine↗

PubMed1982

Alterations in tyrosine hydroxylase activity elicited by raphe nuclei lesions in the rat locus coeruleus: evidence for the involvement of serotonin afferents.

The time course of the variations in tyrosine hydroxylase (TH) activity was measured in the rat locus coeruleus (LC) after lesions of the nucleus raphe dorsalis (NRD), nucleus raphe centralis superior (NRCS) and nucleus raphe pontis (NRP). A certain number of lesions were performed in the raphe magnus (RM), the caudal and rostral NRP and the caudal and rostral NRCS, lateral to raphe nuclei and in adrenalectomized animals. The serotonin (5-HT) content in the LC was also determined after these lesions. Only raphe nuclei producing significant decreases in the 5-HT content in the LC are successful in provoking increases in the TH activity in the LC, thus these results suggest that the noradrenaline (NA) synthesis in the LC may be regulated by 5-HT afferents. Moreover, intraventricular injections of 5,6-dihydroxytryptamine (5,6-DHT) and administration of parachlorophenylalanine (PCPA) also produce significant increases in TH in the LC. After immunotitrations of TH in the LC it was shown that, with exception of a high dose of 5,6-DHT (75 micrograms), all these treatments provoke an increase in the concentration of the enzyme. It therefore seems that one of the functional roles of 5-HT in the LC could be the regulation of the concentration of TH.

5,6-Dihydroxytryptamine↗

PubMed1982

Substance P neurons project from the ventral medulla to the intermediolateral cell column and ventral horn in the rat.

The descending substance P projections from the ventral medulla were studied in the rat. Electrolytic lesions which included the nucleus interfascicularis hypoglossi decreased the substance P-like immunoreactivity (SP-I) in both the intermediolateral cell column and the ventral horn of the spinal cord. Lesions of other ventral medullary areas and midbrain hemisections did not change spinal cord SP-I levels. Intracerebroventricular administration of the serotonin neurotoxin, 5,7-dihydroxytryptamine, reduced the SP-I content of the ventral horn but not of the intermediolateral cell column.

5,7-Dihydroxytryptamine↗

PubMed1983

An analysis of neuronal elements within the median nucleus of the raphe that mediate lesion-induced increases in locomotor activity.

Electrolytic lesions of the median nucleus of the raphe (MR) are known to result in large increases in motor activity. The present studies were concerned with identifying the neuronal elements within or near the MR (e.g. fibers of passage, serotonergic or non-serotonergic cells) which, when destroyed, lead to these increases in ambulation. Groups of rats were given either an electrolytic MR lesion or were injected locally with the serotonin neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) or the excitotoxin ibotenic acid, and their subsequent locomotor activities were compared in the open field and in photocell cages. In a 5 min open field test, rats with either electrolytic or ibotenate lesions of the MR were more active compared to all other groups, although rats in the former group were also more active than those in the latter. In a longer activity test conducted in photocell cages, rats with electrolytic lesions were more active than all other groups during the first 20 min period, after which their activity did not differ from the ibotenate group; however, both of these groups were hyperactive compared to all others. Both electrolytic and ibotenate groups showed exaggerated hyperactivity in response to D-amphetamine. Lesions produced by 5,7-DHT failed to significantly increase either spontaneous or D-amphetamine-induced locomotor activity. When the results from all of the activity measures are considered, it appears that damage to at least two different neuronal populations may be responsible for the hyperactivity observed in MR lesioned rats. However, damage to the serotonergic system does not appear to contribute to these locomotor effects.

5,7-Dihydroxytryptamine↗

PubMed1983

Effects of estrogen on the excitability of neurons projecting from the noradrenergic A1 region to the preoptic and anterior hypothalamic area.

Estradiol benzoate administered to ovariectomized female rats significantly elevated the mean spontaneous firing rate and frequency of successful antidromic propagation into the somatodendritic spike and significantly reduced the strength of post-stimulus inhibition in presumed A1 noradrenergic neurons projecting directly to the preoptic and anterior hypothalamic area. The occurrence of both antidromic spikes and post-stimulus inhibition of the majority of these neurons was completely abolished by the injection of 6-hydroxydopamine but not by 5, 7-dihydroxytryptamine directly into the medial forebrain bundle.

5,7-Dihydroxytryptamine↗

PubMed1983

Evidence for a bulbospinal serotonergic pressor pathway in the rat brain.

The cardiovascular role of spinal serotonin (5-HT) neurones descending from 5-HT cells near the ventrolateral surface of the medulla oblongata was investigated by stimulating these cells in normal animals and in animals with selective chemical ablation of 5-HT nerves. These laterally placed 5-HT nerves fall within the B1 and B3 groups in the medulla and were identified using immunohistochemistry. 5,7-Dihydroxytryptamine (5,7-DHT) was injected into the lateral cerebral ventricle (i.c.v.) to produce a generalized destruction of central 5-HT pathways, with preliminary intraperitoneal administration of desipramine to prevent depletion of noradrenaline stores. In other experiments, 5,7-DHT was injected directly into the cervical spinal cord, after preliminary treatment with desipramine, to produce selective destruction of spinal 5-HT nerves, confirmed both biochemically and immunohistochemically. Electrical stimulation near the lateral 5-HT cells in the B1 and B3 cell groups elicited pressor responses in control (vehicle-injected) rats; the increase in mean arterial pressure was proportional to the intensity and to the frequency of stimulation. Microinjections of kainic acid or L-glutamate at the same sites also produced an increase in mean arterial pressure. Selective destruction of 5-HT nerves, whether produced by i.c.v. or intra-spinal administration of 5,7-DHT, reduced the magnitude of the pressor response to electrical stimulation by over 50%. These experiments suggest the activity of 5-HT nerve cells adjacent to the ventrolateral surface of the medulla oblongata and projecting to the intermediolateral cell column serves to elevate arterial pressure and maintain vasomotor tone.

5,7-Dihydroxytryptamine↗

PubMed1984

Involvement of 5-hydroxytryptamine-containing neurons in antinociception produced by injection of morphine into nucleus raphe magnus or onto spinal cord.

We studied whether antinociception produced by injection of morphine into the nucleus raphe magnus (NRM) or superfusion onto the spinal cord involved serotonergic neurons that descend from brainstem to spinal cord. Involvement of 5-hydroxytryptamine (5-HT)-containing neurons was determined by correlating morphine-induced analgesia with an increase in turnover of 5-HT and by determining if depletion of cord 5-HT with the neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT) could attenuate the antinociceptive effects of morphine. When injected directly into the NRM, 10 micrograms of morphine produced profound analgesia as measured by the paw-pressure technique, and significantly increased the turnover of 5-HT in both posterior medulla and spinal cord. Depletion of cord 5-HT to less than 10% of control concentrations attenuated the antinociceptive effect of morphine injected into the NRM. When various concentrations of morphine (1, 10 or 50 micrograms) were injected directly into the spinal subarachnoid space, a dose-dependent analgesia was observed. No change in 5-HT turnover in spinal cord was observed with any dose of morphine superfused onto the cord. In addition, depletion of cord 5-HT with 5,7-DHT did not alter the analgesic response to either 1 or 10 micrograms of intrathecal morphine. These results suggest that although 5-HT-containing neurons descending from brainstem into spinal cord are involved with analgesia produced by morphine injection into the NRM, they are not involved in the analgesia induced by applying morphine directly to the cord.

5,7-Dihydroxytryptamine↗

PubMed1984

Substance P immunoreactivity released from rat spinal cord after kainic acid excitation of the ventral medulla oblongata: a correlation with increases in blood pressure.

Kainic acid injections into the ventral medulla oblongata of sodium pentobarbital-anesthetized rats caused an almost immediate increase in mean arterial pressure which reached hypertensive levels (greater than 200 mm Hg). Correlated with this rise in blood pressure was a two-fold increase in the amount of SP-like immunoreactivity (SPLI) in spinal cord superfusion samples. Baseline values obtained from a pool of two rats went from approximately 10 pg/10 min to approximately 20 pg/10 min. Rats pretreated with intracerebroventricular injections of the serotonin neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT), were also given kainic acid injections into the ventral medulla. 5,7-DHT did not block pressure response to kainic acid nor the elevation of SPLI in spinal cord superfusates. However, baseline levels of SPLI were decreased by approximately 50% in 5,7-DHT-treated rats. These findings show that activation of the ventral medulla oblongata causes an elevation of SPLI in spinal cord superfusates concomitant with an elevation in mean arterial blood pressure. These responses appear to be independent of serotonergic systems.

5,7-Dihydroxytryptamine↗

PubMed1984

The excitotoxin quinolinic acid is present and unevenly distributed in the rat brain.

The presence of quinolinic acid (2,3-pyridinedicarboxylic acid, QA) in the rat brain has been demonstrated using a mass-spectrometric method. Distribution studies indicate that this molecule is more concentrated in the cortex (2.1 nmol/g wet weight) than in other brain areas. Tryptophan, a possible QA precursor, administered in large doses, increases the cortical content of QA. The contrary occurs when rats are pretreated with p-chlorophenylalanine, a drug capable of decreasing brain tryptophan concentration. The neurotoxin 5,7-dihydroxytryptamine is inactive. Our findings support the idea that QA merits special attention as a potential transmitter and as an endogenous excitotoxin in brain.

5,7-Dihydroxytryptamine↗

PubMed1985

Denervation supersensitivity to 5-hydroxytryptamine in the rat spinal cord is not due to the absence of 5-hydroxytryptamine.

D,L-5-Hydroxytryptophan and 5-HT agonists administered systemically, stimulate motoneuronal discharges as measured by the spontaneous EMG activity of the hindlimbs in paraplegic rats. Denervation supersensitivity is observed after surgical section of the spinal cord or after treatment with 5,7-dihydroxytryptamine (5,7-DHT). Such denervation supersensitivity, however, cannot be reproduced by equivalent depletion of 5-HT by synthesis inhibition or reversed by chronic intrathecal administration of 5-HT agonists. These results suggest that in the anterior horn of the spinal cord, the trigger of denervation supersensitivity to serotonin is not the absence of the neurotransmitter itself but the absence of the terminals or some other compound contained therein.

5,7-Dihydroxytryptamine↗

PubMed1985

Evidence for the involvement of descending noradrenergic pathways in the antinociceptive effect of baclofen.

The role of descending monoaminergic pathways in the antinociceptive effect of baclofen following intraperitoneal (i.p.) administration was investigated by determining the effect of intrathecal (i.t.) administration of neurotoxins [6-hydroxydopamine (6-OHDA) and 5,6-dihydroxytryptamine (5,6-DHT)] and receptor antagonists (phentolamine and methysergide) on baclofen in the tail-flick and hot-plate tests. Pretreatment with 6-OHDA (20 and 50 micrograms) inhibited baclofen antinociception in both tests 4-13 days after treatment. but pretreatment with 5,6-DHT (20 and 100 micrograms) produced a slight increase in the tail-flick test. The higher doses of both neurotoxins produced hyperalgesia in the tail-flick test. In other experiments, baclofen was injected intraperitoneally followed by i.t. amine antagonists when a plateau level of antinociception was attained. Phentolamine (30-100 micrograms) reversed baclofen antinociception in both the tail-flick and hot-plate tests. Methysergide (30-100 micrograms) only reversed the effect of baclofen in doses greater than or equal to 50 micrograms in the tail-flick test. Phentolamine (15 and 30 micrograms) and methysergide (50 micrograms) antagonized the antinociceptive effect of i.t. noradrenaline. Both phentolamine and methysergide produced hyperalgesia in the tail-flick test. However, hyperalgesia per se does not appear to be the only factor responsible for the reversal of baclofen antinociception because dose and agent dissociations between these effects were observed. These results suggest that a major mechanism of action of baclofen in producing antinociception is the activation of noradrenergic pathways descending to the spinal cord.

5,6-Dihydroxytryptamine↗

PubMed1985

The involvement of serotonin neurones in the inhibition of renal nerve activity during desynchronized sleep.

Numerous 5-hydroxytryptamine (5-HT)-containing cell bodies were visualized by fluorescence microscopy in the caudal brainstem rostral to the decussation of the pyramids in a region from which a desynchronized sleep-like pattern of sympathetic activity was obtained in a previous study. In unanaesthetized mid-collicular decerebrated cats recordings were made of sympathetic activity in a renal nerve. The inhibition of renal nerve activity occurring during desynchronized sleep-like state induced by physostigmine was attenuated significantly by procedures which interfered with the pathways from the 5-HT-containing neurones. Small cuts in the dorsolateral funiculus of the cervical spinal cord reduced the inhibition from 43 +/- 6% to 14.0 +/- 3%. Microinjection of 5,7-dihydroxytryptamine into cervical spinal cord reduced the serotonin content of the thoracic cord by 22.4% and attenuated the desynchronized sleep-like state inhibition of renal nerve activity by a similar amount. Depletion of serotonin with p-chlorophenylalanine significantly reduced the inhibition of renal nerve activity during the desynchronized sleep-like state, from 42.5 +/- 5% to 10.0 +/- 2.0%. It was suggested that serotonin-containing neurones are likely to be involved in the inhibition of renal nerve activity occurring during desynchronized sleep.

5,7-Dihydroxytryptamine↗

PubMed1985

Regulation of central alpha-adrenoceptors by serotoninergic denervation.

Alpha 1- and alpha 2-adrenoceptors were assessed by binding studies using [3H]prazosin and [3H]p-aminoclonidine as ligands in membrane preparations from the cortex, hippocampus and hypothalamus of rats, 3 weeks after intracerebroventricular injection of the neurotoxin 5,7-dihydroxytryptamine. Cortical alpha 1 and hippocampal alpha 2 adrenoceptors were significantly increased. Treatment also affected the affinity of cortical alpha 2 adrenoceptors. These results suggest a heterologous, region-specific regulation of both subtypes of central alpha-adrenergic receptors by serotonin.

5,7-Dihydroxytryptamine↗