Biomedical subjects

M Herkenham

Publications and source records attributed to M Herkenham.

At least 37 records · Page 2Linked to original sources

PubMed1999

Localization of central cannabinoid CB1 receptor messenger RNA in neuronal subpopulations of rat dorsal root ganglia: a double-label in situ hybridization study.

In situ hybridization histochemistry was used to show the distribution of messenger RNA for central cannabinoid CB 1 receptors in dorsal root ganglia of the rat. CB1 messenger RNA was highly expressed in neuronal subpopulations of rat dorsal root ganglia. The phenotypes of neurons that express messenger RNA for CB1 were subsequently examined by combining a 35S-labeled ribonucleotide probe for CB1 messenger RNA with digoxigenin-labeled riboprobes for preprotachykinin A (substance P precursor), alpha-calcitonin gene-related peptide and preprosomatostatin (somatostatin precursor) messenger RNAs. Qualitative examination revealed expression of CBI messenger RNA predominantly in medium-and large-sized cells distributed throughout the dorsal root ganglia. The majority of neurons expressing substance P messenger RNA were CB1 messenger RNA negative and smaller in size than the CB1 messenger RNA-positive cells. Only 13% of substance P messenger RNA-positive cells expressed CB1 messenger RNA. A similar degree of co-localization was observed with alpha-calcitonin gene-related peptide: 10% of cells expressing messenger RNA for this neuropeptide were CB1 messenger RNA positive. Co-localization of CB1 and somatostatin messenger RNAs was observed in less than 0.5% of somatostatin messenger RNA-positive cells. The data suggest that subpopulations of neurons in rat dorsal root ganglia are capable of synthesizing cannabinoid receptors and inserting them on terminals in the superficial dorsal horn. These findings provide anatomical evidence for cannabinoid modulation of primary afferent transmission. Although an anatomical basis for cannabinoid-mediated suppression of release of neurogenic peptides from nociceptive primary afferents is provided, our results demonstrate that the majority of CB messenger RNA-positive neurons in the dorsal root ganglia contain transmitters and/or neuromodulators other than the neuropeptides examined herein.

Animals↗

PubMed1999

Cannabinoid receptors undergo axonal flow in sensory nerves.

Cannabinoids modulate nociceptive processing through central and peripheral mechanisms. The present study was conducted to evaluate axonal flow of cannabinoid receptors from the dorsal root ganglion to the periphery and to identify the putative involvement of CB1 and/or CB2 receptor subtypes. The sciatic nerve was tightly ligated to dam the flow of cannabinoid receptors to the periphery. The densities of cannabinoid receptors proximal and distal to one or two tightly constrictive ligatures was evaluated using in vitro receptor binding and high-resolution emulsion autoradiography. In both models, [3H]CP55,940 binding accumulated proximal as opposed to distal to the ligature. These data indicate that axonal transport of cannabinoid receptors to the periphery was occluded by tight constriction of the sciatic nerve. In situ hybridization histochemistry revealed that dorsal root ganglia cells synthesize CB1 but not CB2 receptor messenger RNA. By contrast, CB2 messenger RNA was highly expressed in sections of rat spleen that were processed together with the dorsal root ganglia, as previously described. These data demonstrate that neuronal cannabinoid CB1 receptors are synthesized in cells of the dorsal root ganglia and inserted on terminals in the periphery.

Animals↗

PubMed1998

Temporal and spatial patterns of c-fos mRNA induced by intravenous interleukin-1: a cascade of non-neuronal cellular activation at the blood-brain barrier.

Brain cells responsive to a peripheral immune challenge, identified by in situ hybridization of c-fos mRNA following intravenous administration of the proinflammatory cytokine interleukin-1beta (IL-1) or sterile saline, were investigated at 0.5, 1, and 3 hours postinjection in rats. Doses of IL-1 ranged from 0.05 to 10 microg/kg; induction of c-fos mRNA occurred at > or = 0.5 pg/kg. The majority of IL-1-induced c-fos mRNA-positive cells were non-neuronal cells located in barrier regions of the brain. The cells became radiolabeled in two separate but related spatiotemporal patterns. The first pattern, occurring at 0.5 hour, was characterized by c-fos mRNA labeling of cells of the outer meninges (mainly arachnoid), blood vessels (arteries, veins, and capillaries), and choroid plexus. This activation pattern disappeared at 1 hour. At 3 hours, a second activation pattern appeared in cells located just inside the now quiescent barrier cells. In addition, the circumventricular organs each showed characteristic spatiotemporal labeling patterns resulting from successive activation of specific cell types, with a general spread of activation directed away from the circumventricular organs over time. At 3 hours post IL-1, c-fos and glial fibrillary acidic protein (GFAP) mRNAs showed colocalization in the arcuate nucleus/median eminence/glia limitans region. We propose that the first wave of activation is elicited by blood-borne immune signals, but the second wave is caused by molecules generated within the first set of activated cells. The transduced signal appears to propagate to neighboring receptive cells by extracellular diffusion. In this manner, blood-brain barrier cells can transduce peripheral IL-1 signals in widespread areas of the brain, although the circumventricular organs may be the most effective loci for signal transduction.

Animals↗

PubMed1998

Cyclooxygenase 2 mRNA expression in rat brain after peripheral injection of lipopolysaccharide.

Inducible cyclooxygenase 2 (COX 2) converts arachidonic acid to prostaglandins, which are thought to mediate various peripheral lipopolysaccharide (LPS)-induced central effects, including generation of fever and activation of the hypothalamic-pituitary-adrenal axis. To localize prostaglandin production in the brain following peripheral LPS administration, COX 2 mRNA expression was examined by in situ hybridization histochemistry in rats injected intraperitoneally (i.p.) or intravenously (i.v.) with various doses of LPS or saline. Constitutive expression of COX 2 mRNA was found in neurons of cortex, hippocampus, and amygdala, but not in cells of the blood vessels. COX 2 mRNA levels were not altered in saline-injected animals as compared to non-injected controls. In LPS-injected animals, no consistent changes of neuronal COX 2 mRNA expression were observed. COX 2 mRNA expression appeared ex novo at 0.5-h post-injection in cells closely associated with blood vessels, however, ex novo labeling of the number of labeled cells increased to a peak at 2 h and subsided gradually to basal levels by 24 h. Initially, labeling was observed in cells comprising major surface-lying blood vessels and meninges. Later, vascular and perivascular cells associated with smaller penetrating blood vessels were labeled. This pattern of COX 2 mRNA induction is independent of the route and dose of the LPS injection. The induced COX 2 mRNA producing cells are identified as endothelial and leptomeningeal cells. Changes in COX 2 mRNA expression were not observed in circumventricular organs. These results suggest that peripheral LPS induces a rapid increase in COX 2 production throughout the vasculatures of the brain, which could affect the neuronal activity of widespread brain regions by elevating the levels of prostaglandins.

Animals↗

PubMed1998

Regulation of cannabinoid and mu opioid receptors in rat lumbar spinal cord following neonatal capsaicin treatment.

In vitro receptor binding and quantitative autoradiography were used to determine whether cannabinoid receptors in rat lumbar spinal cord are localized to the central terminals of nociceptive primary afferents. Rats were treated as neonates with capsaicin to destroy sensory C-fibers. The densities of cannabinoid and mu opioid receptors in the spinal cord of the adult rats were compared with age-matched vehicle controls. Neonatal capsaicin produced a moderate but reliable suppression (16%) of [3H]CP55,940 binding to cannabinoid receptors. By contrast, the binding of [3H][D-Ala2-MePhe4,Gly-ol5]enkephalin (DAMGO) to mu receptors was depleted by approximately 60% in near adjacent sections. These data suggest that only a subpopulation of cannabinoid receptors is situated on the central terminals of primary afferent C-fibers. The present data provide anatomical evidence for a dissociation between cannabinoid and mu opioid modulation of sensory transmission at the level of the primary afferent inputs to the spinal cord.

Analgesics, Opioid↗

PubMed1998

Time course and localization patterns of interleukin-1beta messenger RNA expression in brain and pituitary after peripheral administration of lipopolysaccharide.

The inflammatory cytokine interleukin-1 has been implicated as a mediator of many centrally controlled responses, such as fever and increased activity of the hypothalamic-pituitary adrenal axis, after systemic infections. To identify the neuroanatomical loci of brain interleukin-1-producing cells during infection, we investigated interleukin-1beta messenger RNA expression by in situ hybridization histochemistry using a 500 nt ribonucleotide probe applied on brain sections from rats injected intraperitoneally with 2.5 mg/kg bacterial lipopolysaccharide or saline. In control animals, interleukin-1beta messenger RNA was not detectable. In the brains of lipopolysaccharide-injected animals, two temporally and spatially distinct waves of interleukin-1beta messenger RNA induction were observed. First, cell labelling appeared at 0.5 h, peaked at 2 h, and declined at 4-8 h. The labelled cells were concentrated in circumventricular organs--organum vasculosum of the lamina terminalis, subfornical organ, median eminence, and area postrema--and in choroid plexus, meninges, and blood vessels. Second, at 8-12 h, scattered small cells became labelled throughout the entire brain parenchyma; the labelling subsided by 24 h. Labelling was not observed in any neurons. In the pituitary, lipopolysaccharide induced strong interleukin-1beta messenger RNA expression initially in the anterior lobe at 0.5-1 h, and later in the neural lobe at 1-2 h, and subsiding thereafter. The results show that at early time points, peripheral lipopolysaccharide induces interleukin-1beta message production at the blood brain barrier and in circumventricular organs where the blood brain barrier is leaky. After a time delay of 6-10 h, however, interleukin-1beta messenger RNA is primarily expressed by non-neuronal cells of the brain in the brain parenchyma. These results suggest that the source of initial brain IL-1 activity after peripheral lipopolysaccharide injection derives from cells of the blood-brain barrier and the circumventricular organs, and the sustained interleukin-1 activity in the central nervous system thereafter is derived from glia.

Animals↗

PubMed1998

Area postrema removal abolishes stimulatory effects of intravenous interleukin-1beta on hypothalamic-pituitary-adrenal axis activity and c-fos mRNA in the hypothalamic paraventricular nucleus.

This study examined the role of the area postrema (AP) in transducing peripheral immune signals, represented by intravenous (i.v.) interleukin-1beta (IL-1), into neuroendocrine responses. The AP, a circumventricular organ with a leaky blood-brain barrier, lies adjacent to the nucleus of the solitary tract (NTS) in the medulla. The AP was removed by aspiration, and 2 weeks later, AP-lesioned or sham-lesioned rats were injected i.v. with 0.5 microg/kg IL-1 or sterile saline. After 30 min, brains were removed and analyzed for c-fos mRNA levels in various structures implicated in the hypothalamic-pituitary-adrenal axis response to peripheral cytokine challenge. The sham-lesioned animals responded to IL-1 with large elevations in adrenocorticotropic hormone (ACTH) and corticosterone levels in the plasma and c-fos mRNA levels in cells of the AP, NTS, central nucleus of the amygdala, bed nucleus of the stria terminalis, hypothalamic paraventricular nucleus (PVN), and meninges. Prior AP removal abolished the IL-1 -induced increases in ACTH and corticosterone in the plasma and c-fos mRNA levels in the NTS and PVN. However, AP removal had no effect on IL-1-induced increases in c-fos mRNA levels in the other areas examined. The selective AP lesion effects suggest that the AP and adjacent NTS play a pivotal role in transducing a circulating IL-1 signal into hypothalamic-pituitary-adrenal axis activation by a pathway that may be comprised of known anatomical links between the AP, NTS, and corticotropin-releasing hormone neurons of the PVN.

Adrenocorticotropic Hormone↗

PubMed1997

Induction of inhibitory factor kappaBalpha mRNA in the central nervous system after peripheral lipopolysaccharide administration: an in situ hybridization histochemistry study in the rat.

In this study we investigate the mRNA expression of inhibitory factor kappaBalpha (IkappaBalpha) in cells of the rat brain induced by an intraperitoneal (i.p.) injection of lipopolysaccharide (LPS). IkappaB controls the activity of nuclear factor kappaB, which regulates the transcription of many immune signal molecules. The detection of IkappaB induction, therefore, would reveal the extent and the cellular location of brain-derived immune molecules in response to peripheral immune challenges. Low levels of IkappaBalpha mRNA were found in the large blood vessels and in circumventricular organs (CVOs) of saline-injected control animals. After an i.p. LPS injection (2.5 mg/kg), dramatic induction of IkappaBalpha mRNA occurred in four spatio-temporal patterns. Induced signals were first detected at 0.5 hr in the lumen of large blood vessels and in blood vessels of the choroid plexus and CVOs. Second, at 1-2 hr, labeling dramatically increased in the CVOs and choroid plexus and spread to small vascular and glial cells throughout the entire brain; these responses peaked at 2 hr and declined thereafter. Third, cells of the meninges became activated at 2 hr and persisted until 12 hr after the LPS injection. Finally, only at 12 hr, induced signals were present in ventricular ependyma. Thus, IkappaBalpha mRNA is induced in brain after peripheral LPS injection, beginning in cells lining the blood side of the blood-brain barrier and progressing to cells inside brain. The spatiotemporal patterns suggest that cells of the blood-brain barrier synthesize immune signal molecules to activate cells inside the central nervous system in response to peripheral LPS. The cerebrospinal fluid appears to be a conduit for these signal molecules.

Animals↗

PubMed1996

Unilateral LTP triggers bilateral increases in hippocampal neurotrophin and trk receptor mRNA expression in behaving rats: evidence for interhemispheric communication.

Induction of long-term potentiation (LTP) in the dentate gyrus of awake rats triggered a rapid (2 hour) elevation in tyrosine kinase receptor (trkB and trkC) gene expression and a delayed (6-24 hour) increase in brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) gene expression. Depending on the mRNA species, LTP induction led to highly selective unilateral or bilateral increases in gene expression. Specifically, trkB and NT-3 mRNA elevations were restricted to granule cells in the ipsilateral dentate gyrus, whereas bilateral increases in trkC, BDNF, and nerve growth factor (NGF) mRNA levels occurred in granule cells and hippocampal pyramidal cells. Both unilateral and bilateral changes in gene expression were N-methyl-D-aspartate (NMDA) receptor-dependent and LTP-specific. Bilateral electrophysiological recordings demonstrated that LTP was unilaterally induced; this was corroborated by a dramatic unilateral increase in the expression of the immediate early gene zif/268, a marker for LTP, restricted to the ipsilateral granule cells. The results indicate that LTP triggers an interhemispheric communication manifested as selective, bilateral increases in gene expression at multiple sites in the hippocampal network. Furthermore, our findings suggest that physiological plastic changes in the adult brain may involve coordinated, time-dependent regulation of multiple neurotrophin and trk receptor genes.

Animals↗

PubMed1996

Effects of long-term treatment with antidepressant drugs on proopiomelanocortin and neuropeptide Y mRNA expression in the hypothalamic arcuate nucleus of rats.

Antidepressant drugs have in common a delayed onset of clinical efficacy. In rats, long-term, daily administration of four different types of clinically effective antidepressant drugs results in decreased corticotropin releasing hormone (CRH) mRNA expression levels in the hypothalamic paraventricular nucleus (PVN). Because a subpopulation of neuropeptide Y (NPY) and proopiomelanocortin (POMC) neurons in the hypothalamic arcuate nucleus (Arc) projects to the PVN, we measured NPY and POMC mRNA expression in the Arc using in situ hybridization histochemistry at several time points following daily administration of four different antidepressant drugs. After 14 and 56 days of imipramine treatment, Arc NPY mRNA levels are decreased to 85% and 75% of control levels, but are unchanged compared to control after one or five days of treatment. Arc POMC mRNA levels are unchanged compared to controls at 1, 5, 14, or 56 days following imipramine treatment. Unlike after imipramine, Arc NPY and POMC mRNA levels are increased significantly to 134-172% of control following 56-day treatment with the antidepressant drugs fluoxetine, phenelzine, or idazoxan. The divergent effects of imipramine vs the other 3 antidepressant drugs on Arc NPY mRNA expression are similar to the pattern of changes in tyrosine hydroxylase (TH) mRNA expression levels in the locus coeruleus (LC) using the same experimental paradigm, but are different from the unidirectional depressive effects of all four drugs on CRH mRNA expression in the PVN. Thus, the Arc NPY and LC noradrenergic systems may act coordinately in mediating antidepressant effects. The present data are consistent with the delayed onset of clinical efficacy for antidepressant drugs, and suggest that Arc NPY and POMC neurotransmitter systems play a role in the pathophysiology of depression.

Adrenergic alpha-Antagonists↗

PubMed1995

Arcuate nucleus neurons that project to the hypothalamic paraventricular nucleus: neuropeptidergic identity and consequences of adrenalectomy on mRNA levels in the rat.

The possible role that the hypothalamic arcuate nucleus might play in mediating the increase in paraventricular nucleus corticotropin-releasing hormone mRNA levels following adrenalectomy was investigated in two series of experiments. In the first series in situ hybridization histochemistry was used to quantify levels of eight accurate nucleus neuropeptide and neurotransmitter mRNAs in neurons that potentially relay adrenal steroid feedback to the paraventricular nucleus. In the second series of experiments, arcuate neuropeptidergic projections to the hypothalamic paraventricular nucleus were characterized using retrograde tracing in combination with in situ hybridization histochemistry. Despite an increase in paraventricular nucleus corticotropin-releasing hormone (60%) and pituitary proopiomelanocortin mRNA levels (sixfold), arcuate mRNA levels for proopiomelanocortin, neuropeptide Y, somatostatin, galanin, dynorphin, tyrosine hydroxylase, glutamate decarboxylase, and the glucocorticoid receptor were unchanged 14 days following adrenalectomy. Neuropeptidergic characterization of arcuatoparaventricular projections was achieved by injection of the retrograde tracer fluorogold into the paraventricular nucleus; retrogradely labeled neurons were characterized with polyclonal antisera against fluorogold in combination with oligonucleotide probes directed against neuropeptide Y, proopiomelanocortin, or somatostatin. Out of these three arcuate neuropeptide Y mRNA was contained in 18% of the fluorogold-positive neurons in the arcuate, proopiomelanocortin mRNA was contained in 8%, and somatostatin mRNA was contained in 6%. Overall, the results from both experiments suggest that the arcuatoparaventricular neuropeptide Y, proopiomelanocortin, and somatostatin projections are not sensitive to a chronic (14 day) lack of adrenal steroids. These projections as well as the other arcuate neurotransmitter and neuropeptide systems appear not to contribute to the persistent elevations in paraventricular nucleus corticotropin-releasing hormone mRNA levels or pituitary proopiomelanocortin mRNA levels found in 14 day adrenalectomized rats.

Adrenal Glands↗

PubMed1995

The human neostriatum shows compartmentalization of neuropeptide gene expression in dorsal and ventral regions: an in situ hybridization histochemical analysis.

Expression of neuropeptide messenger RNAs in striatal neurons was studied in post mortem human brain tissue by the use of in situ hybridization histochemistry. Clusters of cells expressing high levels of prodynorphin messenger RNA, and less strikingly, preprotachykinin messenger RNA, were prominent in the caudate nucleus and were present but less pronounced in the putamen. Proenkephalin and prosomatostatin messenger RNA-containing cells were more homogeneously distributed throughout the striatum, though the latter were much sparser. The four neuropeptide messenger RNA patterns in the nucleus accumbens were rather homogeneous compared with the dorsal striatum. Of these, prodynorphin messenger RNA showed a higher level of expression per cell in the nucleus accumbens relative to the dorsal striatum. The relationship of neuropeptide-containing cell clusters to the striosomal organization was characterized by looking at the register of these markers with patterns of low acetylcholinesterase activity and dense mu opiate receptor binding. In the caudate and putamen, clusters of cells expressing high levels of dynorphin and preprotachykinin messenger RNAs were clearly in register with the striosomes. The accumbens was defined by high prodynorphin messenger RNA levels, both low and high levels of acetylcholinesterase staining, and very low to absent mu opiate receptor binding. The distribution of high-expressing prodynorphin messenger RNA-containing cells--to the patch compartment and throughout the entire ventral striatum/nucleus accumbens region--defines the limbic domain of the neostriatum and suggests particular relevance to human striatal organization and function, because the distribution of this opioid neuropeptide is considerably more compartmentalized in human than in non-human species.

Acetylcholinesterase↗

PubMed1994

Hypothalamic lesions increase levels of neuropeptide Y mRNA in the arcuate nucleus of mice.

A recent study demonstrated that hypothalamic lesions induced by goldthioglucose (GTG) in mice produced an increase in neuronal immunoreactivity for neuropeptide Y (NPY) in the hypothalamic arcuate nucleus. Since NPY is a potent stimulator of feeding, this increase represented a potential explanation for the hyperphagia seen after GTG lesions. To examine whether or not this increase in NPY immunoreactivity was accompanied by an increase in the mRNA for NPY, in situ hybridization histochemistry for NPY mRNA in control and in lesioned mice was performed. A 47% increase in NPY mRNA levels in the arcuate nucleus was observed in lesioned mice compared with controls, suggesting that an increased expression of the gene for NPY contributes to elevations in hypothalamic NPY after lesioning. This elevation in NPY may, in turn, relate to mechanisms provoking hyperphagia.

Animals↗

PubMed1994

Selective vulnerability in Huntington's disease: preferential loss of cannabinoid receptors in lateral globus pallidus.

Selective neuronal vulnerability is a key feature of the neuropathology of Huntington's disease. We used [3H]CP-55,940, a synthetic cannabinoid, to label cannabinoid receptors in tissue sections from individuals dying with Huntington's disease and from normal control subjects. The density of cannabinoid receptors in striatum and pallidum was measured using quantitative autoradiography. There was a greater loss of cannabinoid receptors on striatal nerve terminals in the lateral pallidum compared to the medial pallidum, in Huntington's disease of all neuropathological grades. The disparity in binding density between the lateral and medial pallidum increased with higher grades of disease. There was also a greater loss of receptors in the lateral pallidum than in the putamen. The disproportionate loss of receptors in the lateral pallidum compared to the putamen increased in magnitude with severity of neuropathological grade. These data support the relative preferential loss or dysfunction of striatal neurons projecting to the lateral pallidum compared to neurons projecting to the medial pallidum. Terminals in the lateral pallidum containing cannabinoid receptors may be affected earlier or more severely than terminals in the medial pallidum, and both pallidal segments may be affected before or more severely than cell bodies or dendrites in the striatum. Terminal loss of markers may represent a response to perikaryal injury or dysfunction, or less likely, may indicate the primary site of neuronal damage in Huntington's disease.

Adult↗

PubMed1994

Cannabinoid receptor binding and messenger RNA expression in human brain: an in vitro receptor autoradiography and in situ hybridization histochemistry study of normal aged and Alzheimer's brains.

The distribution and density of cannabinoid receptor binding and messenger RNA expression in aged human brain were examined in several forebrain and basal ganglia structures. In vitro binding of [3H]CP-55,940, a synthetic cannabinoid, was examined by autoradiography in fresh frozen brain sections from normal aged humans (n = 3), patients who died with Alzheimer's disease (n = 5) and patients who died with other forms of cortical pathology (n = 5). In the structures examined--hippocampal formation, neocortex, basal ganglia and parts of the brainstem--receptor binding showed a characteristic pattern of high densities in the dentate gyrus molecular layer, globus pallidus and substantia nigra pars reticulata, moderate densities in the hippocampus, neocortex, amygdala and striatum, and low densities in the white matter and brainstem. In situ hybridization histochemistry of human cannabinoid receptor, a ribonucleotide probe for the human cannabinoid receptor messenger RNA, showed a pattern of extremely dense transcript levels in subpopulations of cells in the hippocampus and cortex, moderate levels in hippocampal pyramidal neurons and neurons of the striatum, amygdala and hypothalamus, and no signal over dentate gyrus granule cells and most of the cells of the thalamus and upper brainstem, including the substantia nigra. In Alzheimer's brains, compared to normal brains, [3H]CP-55,940 binding was reduced by 37-45% in all of the subfields of the hippocampal formation and by 49% in the caudate. Lesser reductions (20-24%) occurred in the substantia nigra and globus pallidus, internal segment. Other neocortical and basal ganglia structures were not different from control levels. Levels of messenger RNA expression did not differ between Alzheimer's and control brains, but there were regionally discrete statistically significant losses of the intensely expressing cells in the hippocampus. The reductions in binding did not correlate with or localize to areas showing histopathology, estimated either on the basis of overall tissue quality or silver staining of neuritic plaques and neurofibrillary tangles. Reduced [3H]55,940 binding was associated with increasing age and with other forms of cortical pathology, suggesting that receptor losses are related to the generalized aging and/or disease process and are not selectively associated with the pathology characteristic of Alzheimer's disease, nor with overall decrements in levels of cannabinoid receptor gene expression.

Aged↗

PubMed1994

Repeated electroconvulsive shock produces long-lasting increases in messenger RNA expression of corticotropin-releasing hormone and tyrosine hydroxylase in rat brain. Therapeutic implications.

Electroconvulsive shock (ECS) is a highly effective therapy for the treatment of major depression, but its mechanisms of action are not known. We report that repeated ECS in rats produces enduring changes in two clinically relevant stress-responsive brain systems: (a) the hypothalamic-pituitary-adrenal axis regulated by corticotropin-releasing hormone (CRH) in the paraventricular nucleus; and (b) the NE system in the locus coeruleus regulated by tyrosine hydroxylase (TH). CRH and TH mRNA levels in these brain regions were assessed by in situ hybridization histochemistry. A single interaural ECS elevated TH but not CRH mRNA measured 24 h later. Repeated daily treatments (3, 7, or 14) elevated both mRNAs, maximally with 7, correlating with the time course of clinical efficacy. The elevations persisted for 3 (CRH) or 8 wk (TH) after the ECS. No other therapeutic treatment is known to produce such long-lasting changes in central nervous system gene expression. The time course of events (delayed onset, long duration) implicate CRH as a principal mediator of the antidepressant effects of ECS. The locus coeruleus-NE system may be important in initiating the central nervous system response.

Analysis of Variance↗

PubMed1994

Systemic interleukin-1 induces early and late patterns of c-fos mRNA expression in brain.

This study was designed to examine the mechanisms by which systemic interleukin-1 affects neuroendocrine systems in the brain. Intraperitoneal injections of interleukin-1 beta (1.25 micrograms/rat) were administered to rats. One or three hours after injection, the expression levels of the immediate-early gene c-fos and of genes for several neuropeptides, receptors, and enzymes were examined by in situ hybridization histochemistry. In the brainstem at 1 hr, c-fos mRNA was elevated in the area postrema and nucleus of the solitary tract, but not in the locus coeruleus. At 3 hr, the c-fos mRNA levels had increased further in the nucleus of the solitary tract. Rostrally, elevations in c-fos mRNA levels were found in the hypothalamic and thalamic paraventricular nuclei, central nucleus of amygdala, bed nucleus of the stria terminalis, and medial preoptic area, peaking at 1 hr and diminishing at 3 hr. In addition, at 3 hr a new pattern of c-fos activity emerged--the arcuate nucleus and cells at the external margins throughout the brain now expressed c-fos mRNA. Corticotropin-releasing hormone mRNA levels were doubled in the paraventricular nucleus at 1 and 3 hr, concomitant with elevations in plasma adrenocorticotrophic hormone (ACTH) and corticosterone. Tyrosine hydroxylase mRNA levels in the brainstem did not change. The c-fos mRNA induction patterns reveal a temporally dynamic response to interleukin-1 administration. We propose that the early set of structures responding to interleukin-1 initiates the neuroendocrine response to cytokines. Coactivation of the area postrema and nucleus of the solitary tract may reflect entry into the brain and neural transduction of the peripheral signal. The late set--including the nucleus of the solitary tract, arcuate nucleus, and the brain's edge--may reflect cellular activation along the diffusion routes traveled by interleukin-1 or a bioactive transduction product, because the pattern of edge labeling is similar to the autoradiographic pattern of flow lf radiolabeled tracer substances in the cerebrospinal fluid. The late c-fos mRNA response to interleukin-1, therefore, may represent a demonstration of information transfer in the parasynaptic mode, also known as volume transmission.

Animals↗

PubMed1994

Localization of cannabinoid receptors and nonsaturable high-density cannabinoid binding sites in peripheral tissues of the rat: implications for receptor-mediated immune modulation by cannabinoids.

[3H]CP-55,940, a high-affinity cannabinoid receptor ligand, was used for in vitro binding and autoradiography in peripheral tissues in the rat. Specific cannabinoid receptor binding was found to be restricted to components of the immune system, i.e., spleen, lymph nodes and Peyer's patches. Displacement studies showed that this binding is identical (similar Kd and structure-activity profile) to that in brain. Cannabinoid receptors in the immune system are confined to B lymphocyte-enriched areas, i.e., the marginal zone of the spleen, cortex of the lymph nodes and nodular corona of Peyer's patches. Specific binding is absent in T lymphocyte-enriched areas, such as the thymus and periarteriolar lymphatic sheaths of the spleen. Certain macrophage-enriched areas, i.e., liver and lung, lack specific binding. Thus, the single peripheral cell type that may contain cannabinoid receptors is the B lymphocyte. Numerous sites have dense binding that could not be displaced by excess unlabeled drug. These nonspecific sites were found in the liver, adrenal glands and sebaceous glands, which are high in fat content, and in the heart, pancreas, components of the male and female reproductive systems and the epithelium of the esophagus. Thus, the highly lipophilic nature of cannabinoids does not appear to be the sole determinant of nonspecific binding. The data suggest that cannabinoids may exert specific receptor-mediated actions on the immune system of rats. Perhaps, also at high concentrations, cannabinoids exert membrane effects at sites where they are sequestered nonspecifically.

Adjuvants, Immunologic↗