Biomedical subjects

T Hökfelt

Publications and source records attributed to T Hökfelt.

At least 19 recordsLinked to original sources

PubMed2003

Galanin expression in adult human dorsal root ganglion neurons: initial observations.

Human dorsal root ganglia (DRGs) were obtained during various procedures and processed for single and double in situ hybridisation using oligonucleotide probes complementary to three peptide mRNAs. Some postmortem ganglia were also analysed. In donor (unlesioned) DRGs 12.5% of the neuron profiles (NPs) were galanin mRNA-positive (mRNA(+)), 47.5% calcitonin gene-related peptide (CGRP) mRNA(+) and 32.7% substance P mRNA(+). The corresponding percentages for cervical/thoracic DRGs from patients suffering from severe brachial plexus injury were 32.8%, 57.4% and 34.5%, respectively. In these DRGs a high proportion of the galanin mRNA(+) NPs contained CGRP mRNA and substance P mRNA. In DRGs from a patient with migraine-like pain a comparatively small proportion expressed galanin, whereas in DRGs from a herpes zoster patient galanin mRNA(+) NPs were comparatively more frequent. The results from human postmortem DRGs revealed only weak peptide mRNA signals. The present results demonstrate that galanin is expressed in DRGs not only in a number of animal species including monkey as previously shown, but also in a considerable proportion of human DRG neurons, often together with CGRP and substance P, and mostly in small neurons. Thus, galanin may play a role in processing of sensory information, especially pain, in human DRGs and dorsal horn. However, to what extent a similarly dramatic upregulation of galanin expression can be seen after peripheral nerve lesion in man, as has been reported for rat, mouse and monkey, remains to be analysed.

Adult↗

PubMed2003

Neuropeptide y targets in the hypothalamus: nitric oxide synthesizing neurones express Y1 receptor.

Neuropeptide Y (NPY)-expressing neurones in the arcuate nucleus densely innervate many hypothalamic nuclei. To determine the neurochemical phenotype of target neurones for NPY, we studied the immunohistochemical localization of the NPY Y1 receptor (Y1R) in discrete subpopulations of neurones in the rat hypothalamus. Among several tested populations, including hypocretin/orexin-, melanin-concentrating hormone (MCH)- and nitric oxide synthase (NOS)-positive neurones, only the latter were found to coexpress the Y1R. Numerous Y1R/NOS-positive neurones were found as a densely packaged group of cells located ventrolateral to the ventromedial nucleus, forming a band ascending towards the fornix. Lower numbers of Y1R/NOS-positive neurones were found in the perifornical area and in the peri- and paraventricular nuclei. Expression of the Y1R gene was found in the same locations in the mouse by colocalizing beta-galactosidase, a Y1R gene reporter, with NOS in a Y1R knockout mouse. To explore possible downstream targets of NO in the rat hypothalamus, the NO-regulated molecule cGMP was analysed immunohistochemically after incubation of brain slices with sodium nitroprusside, an NO donor. We observed several cGMP-positive cell bodies in the arcuate nucleus, cGMP-positive blood vessels and a cGMP-positive network of thin fibres, some of which colocalized with choline acetyltransferase.

Animals↗

PubMed2002

Expression of the neuropeptide Y Y1 receptor in the CNS of rat and of wild-type and Y1 receptor knock-out mice. Focus on immunohistochemical localization.

The distribution of neuropeptide Y (NPY) Y1 receptor-like immunoreactivity (Y1R-LI) has been studied in detail in the CNS of rat using a rabbit polyclonal antibody against the C-terminal 13 amino acids of the rat receptor protein. The indirect immunofluorescence technique with tyramide signal amplification has been employed. For specificity and comparative reasons Y1 knock-out mice and wild-type controls were analyzed. The distribution of Y1R mRNA was also studied using in situ hybridization. A limited comparison between Y1R-LI and NPY-LI was carried out.A widespread and abundant distribution of Y1R-LI, predominantly in processes but also in cell bodies, was observed. In fact, Y1R-LI was found in most regions of the CNS with a similar distribution pattern between rat and wild-type mouse. This staining was specific in the sense that it was absent in adjacent sections following preadsorption of the antibody with 10(-5) M of the antigenic peptide, and that it could not be observed in sections of the Y1 KO mouse. In contrast, the staining obtained with an N-terminally directed Y1R antiserum did not disappear, strongly suggesting unspecificity. In brief, very high levels of Y1R-LI were seen in the islands of Calleja, the anterior olfactory nucleus, the molecular layer of the dentate gyrus, parts of the habenula, the interpeduncular nucleus, the mammillary body, the spinal nucleus of the trigeminal, caudal part, the paratrigeminal nucleus, and superficial layers of the dorsal horn. High levels were found in most cortical areas, many thalamic nuclei, some subnuclei of the amygdaloid complex, the hypothalamus and the nucleus of the stria terminalis, the nucleus of the solitary tract, the parabrachial nucleus, and the inferior olive. Moderate levels of Y1R-LI were detected in the cornu Ammonis and the subicular complex, many septal, some thalamic and many brainstem regions. Y1R staining of processes, often fiber and/or dot-like, and occasional cell bodies was also seen in tracts, such as the lateral lemniscus, the rubrospinal tract and the spinal tract of the trigeminal. There was in general a good overlap between Y1R-LI and NPY-LI, but some exceptions were found. Thus, some areas had NPY innervation but apparently lacked Y1Rs, whereas in other regions Y1R-LI, but no or only few NPY-positive nerve endings could be detected. Our results demonstrate that NPY signalling through the Y1R is common in the rat (and mouse) CNS. Mostly the Y1R is postsynaptic but there are also presynaptic Y1Rs. Mostly there is a good match between NPY-releasing nerve endings and Y1Rs, but 'volume transmission' may be 'needed' in some regions. Finally, the importance of using proper control experiments for immunohistochemical studies on seven-transmembrane receptors is stressed.

Animals↗

PubMed2002

Expression of microsomal glutathione S-transferase type 3 mRNA in the rat nervous system.

Microsomal glutathione S-transferase type 3 (MGST3) is a recently identified member of a large superfamily of enzymes involved in biotransformation of xenobiotics and biosynthesis of eicosanoids, including prostaglandins and leukotrienes. Using in situ hybridization histochemistry and reverse transcription polymerase chain reaction, we characterized the expression of MGST3 mRNA in the rat nervous system based on the cloned rat MGST3 gene, under normal conditions and after systemic administration of lipopolysaccharide (LPS). The MGST3 mRNA seemed to be confined to neurons. The broad distribution in the brain was characterized by a strong signal in the hippocampal formation and in the nuclei of the cranial nerves. A moderate signal was found in the cortex, thalamus, amygdala and substantia nigra and a weak signal in the hypothalamus. Motoneurons in the spinal cord and sensory neurons in dorsal root ganglia displayed strong MGST3 mRNA signal. No significant changes in the level of expression of MGST3 mRNA in the brain were found 1, 3 or 6 h after LPS administration. The pattern of distribution of MGST3 mRNA in the rat nervous system and the lack of response to LPS do not support a role for MGST3 in the biosynthesis of proinflammatory eicosanoids but rather suggest other functions, perhaps in metabolic detoxication and neuroprotection.

Animals↗

PubMed2001

Glutamate release from adult primary sensory neurons in culture is modulated by growth factors.

The aim of this study was to examine possible modulatory effects of some trophic molecules, i.e. nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and basic fibroblast growth factor (bFGF), on potassium (K(+))-, bradykinin (BK)- or capsaicin (CAPS)-evoked release of glutamate (GLU) from dorsal root ganglion (DRG) neurons in vitro. BK (0.5 and 1 microM) induced a dramatic and significant increase in glutamate release. Neither CAPS nor K(+) (60 mM) produced any significant increase of GLU release vs. basal levels during a 5-min stimulation. The BK-evoked release of GLU was almost completely blocked by HOE 140, a selective BK2-receptor antagonist at high doses. Basal release of GLU was significantly reduced in cultures grown in the presence of bFGF, whereas BDNF and NGF had no significant effect. Incubation with growth factors generally decreased the BK-stimulated GLU release, an effect most pronounced for bFGF, which completely blocked BK-stimulated release. The rise in intracellular [Ca(2+)] following stimulation with BK (100 nM-1 microM), potassium (60 mM) or ATP (10 microM) was also studied using a Ca(2+)-sensitive indicator, Fura-2, in cultures grown in basal medium with or without bFGF. None of the bFGF-treated cells exhibited strong Ca(2+) responses to BK or ATP stimulation, while 10-20% of the responding cells grown in basal medium exhibited strong responses. The K(+)-induced increase of [Ca(2+)] did not vary between the different groups. The present findings suggest that sensory neurotransmission involving glutamate may be modulated by growth factors and that regulation of intracellular Ca(2+) homeostasis may be a contributing factor.

Animals↗

PubMed2001

Distribution of an orphan G-protein coupled receptor (JP05) mRNA in the human brain.

JP05, also called GPR72 or GIR, is an orphan G-protein-coupled receptor, GPCR, showing significant structural similarity to the tachykinin receptors. The anatomical distribution of JP05 mRNA was first described in the central nervous system of the mouse, and recently the human JP05 orphan receptor gene has been cloned. In the present study the distribution of JP05 mRNA was examined in the human forebrain using in situ hybridization analysis. The results revealed a wide but discrete distribution of the transcript with strongly JP05 mRNA expressing cells, presumably neurons, present in the cerebral cortex (layer II), hippocampus (pyramidal CA3 neurons and granule cells), amygdala (basal and periamygdaloid cortical nuclei), in the endopiriform nucleus, diagonal band of Broca, thalamus (nucleus reuniens, parafascicular nucleus) and hypothalamus (posterior, dorsal, and around the medial mammillary). Weaker signals were detected in the deeper cortical layers and throughout the striatum. A few positive cells were evident in the raphe but not in the substantia nigra or pontine nuclei. The results indicate significant similarities between human and mouse brain with regard to JP05 mRNA expression. The distribution patterns of JP05 mRNA in the human brain suggest involvement in control of emotions and of neuroendocrine, cognitive and motor functions.

Brain↗

PubMed2001

Effects of galanin receptor agonists on locus coeruleus neurons.

Galanin exerts an inhibitory effect on locus coeruleus (LC) neurons via a postsynaptic, as yet unidentified galanin receptor. Using an in vitro intracellular recording technique the effect of two galanin receptor agonists on LC neurons was investigated. Bath application of [Sar(1), D-Ala(12)]gal(1-16)-NH(2) (AR-M961), an agonist both at galanin R1 and R2 (GALR1, GALR2) receptors, evoked a reversible membrane hyperpolarization and inhibition of spike discharge in all LC neurons tested (n=42). The action of AR-M961 was blocked by tetraethylammonium chloride. Hyperpolarizing responses induced by AR-M961 were retained in the presence of tetrodotoxin and high Mg(2+)/low Ca(2+) media. The selective GALR2 agonist Gal(2-11)-NH(2) (AR-M1896) only caused inhibition of spike discharge and a slight hyperpolarization in 26 of 34 LC neurons tested, and was on a molar basis much weaker than AR-M961. These results suggest that it mainly is the GALR1 receptor that mediates hyperpolarization of LC neurons.

Action Potentials↗

PubMed2001

Suppressed kindling epileptogenesis in mice with ectopic overexpression of galanin.

The neuropeptide galanin has been shown to suppress epileptic seizures. In cortical and hippocampal areas, galanin is normally mainly expressed in noradrenergic afferents. We have generated a mouse overexpressing galanin in neurons under the platelet-derived growth factor B promoter. RIA and HPLC analysis revealed up to 8-fold higher levels of galanin in transgenic as compared with wild-type mice. Ectopic galanin overexpression was detected especially in dentate granule cells and hippocampal and cortical pyramidal neurons. Galanin-overexpressing mice showed retardation of seizure generalization during hippocampal kindling, a model for human complex partial epilepsy. The high levels of galanin in mossy fibers found in the transgenic mice were further increased after seizures. Frequency facilitation of field excitatory postsynaptic potentials, a form of short-term synaptic plasticity assessed in hippocampal slices, was reduced in mossy fiber-CA3 cell synapses of galanin-overexpressing mice, indicating suppressed glutamate release. This effect was reversed by application of the putative galanin receptor antagonist M35. These data provide evidence that ectopically overexpressed galanin can be released and dampen the development of epilepsy by means of receptor-mediated action, at least partly by reducing glutamate release from mossy fibers.

Animals↗

PubMed2001

Expression of neurotrophin receptors in rat testis. Upregulation of TrkA mRNA with hCG treatment.

We report the expression of TrkA, TrkB and TrkC mRNAs in adult rat testis. With in situ hybridisation a low signal for TrkB and TrkC could be seen in postmeiotic cells of the seminiferous epithelium, whereas no signal for TrkA could be observed in untreated animals. Animals treated with hCG showed an induction of TrkA mRNA in premeiotic cells 12 h after the treatment, whereas an injection with EDS had no effect on the expression of Trk mRNAs. With the RNAse protection assay a low signal for TrkA was seen in whole testis of hCG treated animals. In staged tubules low expression was seen at stages VII-XI of untreated animals. Animals injected with hCG revealed that TrkA induction was highest during stages VIIcd and VIII of the cycle. The distinct expression pattern of these high-affinity neurotrophin receptors suggests different roles for neurotrophins during spermatogenesis. Induction of TrkA mRNA by hCG suggests that high-affinity binding of NGF during stages VIIcd-VIII in premeiotic cells is under control of the hypothalamic-pituitary-testicular axis.

Animals↗

PubMed2001

Microdialysis in freely moving mice: determination of acetylcholine, serotonin and noradrenaline release in galanin transgenic mice.

In the present study, we describe micro-surgical methods for simultaneous implantation of a microdialysis probe and an intraventricular injection cannula via their respective guide cannulas into the mouse brain. Basal and stimulated release of acetylcholine (ACh), serotonin (5-HT) and noradrenaline (NA) was determined in the ventral hippocampus of freely moving mice. NA and 5-HT were determined in one run by a newly developed HPLC method based on precolumn derivatization with benzylamine and fluorescence detection. The mice with a loss-of-function mutation of the galanin gene (KO) and the mice that over-expressed galanin (OE) were studied. No significant differences in basal, potassium-stimulated or scopolamine-induced extracellular ACh levels were observed in 4-month-old wild-type (WT) and KO mice. In the aged, 10-month-old animals, the basal extracellular ACh levels were significantly reduced in both WT and KO groups. Galanin (1 nmol i.c.v.) caused a significant reduction of basal extracellular NA by about 40% in both WT and galanin OE mice, however, in the latter group the effect was delayed by almost 2 h. A 10-min forced swimming stress caused a higher increase in release of NA and 5-HT in the OE group than in the corresponding WT mice. Finally, venlafaxin (10 mg/kg i.p.) increased extracellular NA to 400% of the control values in the CBA mice, but only to 250% in the C57BL mice. It is concluded that galanin may play an important role in the cholinergic mechanisms underlying cognitive disorders. Furthermore, modulation by galanin and by behavioral activation, of NA and 5-HT neurotransmission in galanin over-expressing mice indicates its possible role in the aetiology of mood disorders.

Acetylcholine↗

PubMed2001

Receptor subtype-specific pronociceptive and analgesic actions of galanin in the spinal cord: selective actions via GalR1 and GalR2 receptors.

Galanin is a 29-aa neuropeptide with a complex role in pain processing. Several galanin receptor subtypes are present in dorsal root ganglia and spinal cord with a differential distribution. Here, we describe a generation of a specific galanin R2 (GalR2) agonist, AR-M1896, and its application in studies of a rat neuropathic pain model (Bennett). The results show that in normal rats mechanical and cold allodynia of the hindpaw are induced after intrathecal infusion of low-dose galanin (25 ng per 0.5 microl/h). The same effect is seen with equimolar doses of AR-M1896 or AR-M961, an agonist both at GalR1 and GalR2 receptors. In allodynic Bennett model rats, the mechanical threshold increased dose-dependently after intrathecal injection of a high dose of AR-M961, whereas no effect was observed in the control or AR-M1896 group. No effect of either of the two compounds was observed in nonallodynic Bennett model rats. These data indicate that a low dose of galanin has a nociceptive role at the spinal cord level mediated by GalR2 receptors, whereas the antiallodynic effect of high-dose galanin on neuropathic pain is mediated by the GalR1 receptors. Thus, a selective GalR1 agonist may be used to treat neuropathic pain.

Analgesics, Non-Narcotic↗

PubMed2001

Effect of LPS administration on the expression of POMC, NPY, galanin, CART and MCH mRNAs in the rat hypothalamus.

Anorexia and weight loss are manifestations of inflammation seen both in patients and in experimental animal models such as the lipopolysaccharide (LPS)-treated rat. Using in situ hybridization, the levels of mRNAs encoding proopiomelanocortin (POMC), neuropeptide Y (NPY), galanin, melanin-concentrating hormone (MCH) and cocaine- and amphetamine-regulated transcript (CART) were investigated in the rat hypothalamus after a single intraperitoneal dose (125 microg/kg) of LPS. Four hours after LPS injection the food intake was significantly decreased. POMC and CART mRNA levels were increased in the arcuate nucleus, and MCH, CART and galanin mRNAs were all decreased in the lateral hypothalamic area in LPS-treated rats. Levels of mRNAs for NPY and galanin in the arcuate nucleus, and for MCH and CART in the zona incerta did not change significantly after LPS treatment. These findings support the hypothesis that LPS-induced factors mediate signalling to the POMC/CART neurons in the arcuate nucleus which could lead to reduced food intake by decreasing MCH, CART and galanin synthesis in target lateral hypothalamic neurons.

Animals↗

PubMed2001

Distribution of cGMP in guinea pig autonomic ganglia after stimulation with sodium nitroprusside.

Nitric oxide (NO) is an intercellular messenger molecule in the nervous system and exerts its action in many regions by generating cyclic GMP (cGMP) via soluble guanylyl cyclase. In this study, on the male guinea pig, we have analyzed the localization of cGMP in some autonomic ganglia with immunohistochemistry after stimulation with sodium nitroprusside (SNP) as NO donor, and made correlations with the NO synthesizing enzyme NO synthase (NOS), tyrosine hydroxylase (TH) and some neuropeptides. The putative target neurons for NO were examined in the anterior pelvic ganglia (APGs), as well as some pre- and paravertebral sympathetic ganglia. The results show that cGMP-like immunoreactivity (LI) in the APG was in most cases observed in the TH-positive, NOS-negative neuron population after SNP stimulation, whereas the NOS-expressing cholinergic population mostly lacked detectable cGMP-LI. In the pre- and paravertebral ganglia, SNP stimulation increased cGMP levels to a much lesser extent than in the APGs. cGMP was also observed in blood vessels, in the ganglion capsule, and in some cases. possibly in satellite cells. We propose, as one alternative, that there is a functional, intraganglionic regulatory loop between the parasympathetic and sympathetic divisions of the APG, using the NO/cGMP pathway.

Animals↗

PubMed2001

Galanin enhances noradrenaline-induced outward current on locus coeruleus noradrenergic neurons.

Interactions between galanin and noradrenaline (NA) were studied in a locus coeruleus (LC) slice preparation using intracellular recording technique. Both galanin (10-100 nM) and NA induced an outward current. Idazoxan, an alpha2-adrenoceptor antagonist, blocked the NA- but not the galanin-induced outward current, indicating that different receptors mediate these responses. Moreover, the outward current induced by NA was enhanced and prolonged by preincubation with a low concentration of galanin (0.05-0.1 nM), which had no detectable effect on the membrane current by itself. This sensitizing effect may be of physiological importance and could be caused by galanin released from dendrites and soma of galanin/NA neurons and/or from galanin afferents. Thus, besides a direct action of galanin on locus coeruleus neurons, our results also indicate an indirect, modulating effect.

Adrenergic alpha-Agonists↗

PubMed2001

Expression and regulation of cholecystokinin and cholecystokinin receptors in rat nodose and dorsal root ganglia.

Cholecystokinin (CCK) is an important satiety factor, acting via the vagus nerve to influence central feeding centers. CCK binding sites have been demonstrated in the vagal sensory nodose ganglion and within the nerve proper. Using in situ hybridization, expression of the CCK(A) and (B) receptors (Rs), as well as of CCK itself, was studied in the normal nodose ganglion (NG), and after vagotomy, starvation and high-fat diet. CCK(A)-R mRNA expression in dorsal root ganglia (DRGs) was also explored. In the NG, 33% of the neuron profiles (NPs) contained CCK(A)-R mRNA and in 9% we observed CCK(B)-R mRNA. CCK mRNA was not found in normal NGs. Peripheral vagotomy decreased the number of CCK(A)-R mRNA-expressing NPs, dramatically increased the number of CCK(B)-R mRNA, and induced CCK mRNA and preproCCK-like immunoreactivity in nodose NPs. No significant differences in the number of NPs labelled for either mRNA species were detected following 48 h food deprivation or in rats fed a high-fat content diet. In DRGs, 10% of the NPs expressed CCK(A)-R mRNA, a number that was not affected by either axotomy or inflammation. This cell population was distinct from neurons expressing calcitonin gene-related peptide mRNA. These results demonstrate that the CCK(A)-R is expressed by both viscero- and somatosensory primary sensory neurons, supporting a role for this receptor as a mediator both of CCK-induced satiety and in sensory processing at the spinal level. The stimulation of CCK and CCK(B)-R gene expression following vagotomy suggests a possible involvement in the response to injury for these molecules.

Animals↗

PubMed2001

The expression of calcitonin gene-related peptide in dorsal horn neurons of the mouse lumbar spinal cord.

Using immunohistochemistry and in situ hybridization the expression of calcitonin gene-related peptide (CGRP) was studied in the mouse spinal cord under normal conditions and after unilateral rhizotomy and after local colchicine treatment. Under normal conditions a dense plexus of CGRP-immunoreactive (IR) fibres was observed in the superfical layers of dorsal horns with lower numbers of fibers in deeper laminae. Seven days after unilateral rhizotomy, there was a marked reduction of CGRP-IR fibres in the ipsilateral superfical layers and distinctly CGRP-IR neurons could be detected in the ipsilateral lamina III. CGRP mRNA-positive neurons were observed in lamina III in both the ipsilateral and contralateral dorsal horn. Colchicine treatment did not markedly increase the number of CGRP-IR neurons. The results suggest that CGRP is synthesized in local dorsal horn neurons of the mouse, and these neurons presumably participate in sensory processing.

Animals↗

PubMed2001

Intrathecal administration of PNA targeting galanin receptor reduces galanin-mediated inhibitory effect in the rat spinal cord.

Peptide nucleic acids (PNA) are nucleic acid analogues containing neutral amide backbone, forming stable and tight complexes with complementary DNA/RNA. However, it is unclear whether unmodified PNA can efficiently penetrate neuronal tissue in order to act as antisense reagent. Here we show that intrathecal (i.t.) injection of an unmodified antisense PNA complementary to the rat galanin receptor type 1 (GalR1) mRNA is able to block the inhibitory effect of i.t. administered galanin on spinal nociceptive transmission. Autoradiographic ligand binding studies using [125I]galanin show that the unmodified PNA is able to reduce the density of galanin binding sites in the dorsal horn. Thus, unmodified PNA applied i.t. appears to function as an effective antisense reagent in rat spinal cord in vivo.

Animals↗

PubMed2001

Mice over-expressing galanin have elevated heat nociceptive threshold.

The neuropeptide galanin may have a role in modulation of nociceptive input at spinal level. Here we report that mice over-expressing galanin exhibit significant elevation of nociceptive threshold to thermal stimulation in comparison to wild-type mice as assessed by the tail flick and paw heat irradiation tests. No change in response to mechanical or cold stimulation was seen. The elevated heat nociceptive threshold in the galanin over-expressing mice was reversed by intrathecal application of the putative galanin receptor antagonist M-35, galanin-(1-12)-pro-bradykinin-(2-9). The results thus support that galanin has an inhibitory function in rodent spinal cord.

Animals↗