Time-course of neuropeptide changes in peri-ischemic zone and amygdala following focal ischemia in rats

Cardiovascular Manifestations of Acute Intracranial Lesions: Pathophysiology, Manifestations, and Treatment

The objective of this article was to review the effects of acute intracranial lesions on myocardial function. The authors reviewed scientific and clinical literature retrieved from a computerized MEDLINE search from January 1965 through January 2002. Pertinent literature was referenced, including clinical and laboratory investigations, to demonstrate the effects of acute intracranial lesions on the cardiovascular system. The literature was reviewed to summarize the mechanisms of cardiac damage and clinical manifestations and treatment of cardiovascular dysfunction caused by acute intracranial lesions. Myocardial damage and rhythm disturbances were shown to occur with acute intracranial neurological disease. The subgroup of patients used in this study formed a substantial pool of cardiac donors for cardiac transplantation. The pathophysiology of myocardial dysfunction and the optimal management continues to be a source of debate. In this article, the authors will review the anatomy, the available evidence of the pathophysiology, and the management of this complex group of patients. They will also discuss areas that need to be further investigated. Cardiovascular effects of acute intracranial lesions are common and contribute to increased morbidity and mortality.

Role of estrogen in central nuclei mediating stroke-induced changes in autonomic tone

The current investigation examined the role of estrogen in central autonomic regulatory nuclei on the autonomic dysfunction resulting from middle cerebral artery occlusion (MCAO). Experiments were done in anaesthetized male Sprague-Dawley rats. The effect of MCAO on autonomic tone was assessed by monitoring vagal and renal efferent nerve activities before and following systemic administration of either estrogen or saline and the bilateral microinjection of the estrogen receptor antagonist, ICI 182, 780, into several autonomic nuclei (the intrathecal space of the spinal cord, nucleus tractus solitarius, nucleus ambiguus, rostral ventrolateral medulla, parabrachial nucleus, central nucleus of the amygdala or ventral posteromedial thalamus). Autonomic reflex function was evoked using intravenous injection of increasing doses of phenylephrine (0.025-0.1 mg/kg) and the peak changes in heart rate and blood pressure were plotted to obtain the baroreflex sensitivity. The presence of ICI 182, 780 in the intrathecal space of the spinal cord, nucleus ambiguous, nucleus tractus solitarius, rostral ventrolateral medulla, parabrachial nucleus, or central nucleus of the amygdala prior to the administration of estrogen resulted in a significant attenuation (ranging from 79% to 94 %) in the estrogen-induced recovery of autonomic function following MCAO. Blocking estrogen receptors in the ventral posteromedial thalamus had no effect on the ability of estrogen to prevent the MCAO-induced changes in autonomic function. These results suggest that the estrogen-mediated recovery of autonomic function following MCAO is dependent on the availability of estrogen receptors in several forebrain and brainstem autonomic nuclei.

Stroke-induced changes in estrogen release and neuronal activity in the parabrachial nucleus of the male rat

Recent investigations have provided evidence to suggest exogenous estrogen administration into autonomic nuclei prevents or reverses the autonomic dysfunction observed after middle cerebral artery occlusion (MCAO) in male rats. Because estrogen seems to be a potent neuroprotectant against autonomic dysfunction, it is our hypothesis that endogenous estrogen levels within autonomic nuclei will increase in response to stroke. Therefore, in this investigation, in vivo microdialysis was used to simultaneously measure the concentration of estrogen in the plasma and in the parabrachial nucleus (PBN) of male Sprague-Dawley rats after MCAO. Analysis of dialysate samples before MCAO and in sham-operated controls revealed a baseline concentration of estrogen in the PBN (38 +/- 3 pg/mL; n = 36), which was significantly greater than that found in plasma (22 +/- 6 pg/mL; n = 6; P < .05). The concentration of estrogen in the PBN was significantly increased immediately after MCAO (85 +/- 4 pg/mL; n = 7; P < .05) but then decreased to below pre-MCAO values (12 +/- 2 pg/mL; n = 7; P < .05) by 90 minutes after MCAO and remained below baseline levels until the end of the experiment (240 minutes post-MCAO). No changes in plasma estrogen levels were detected at any time point after MCAO. In addition, extracellular electrophysiological recordings from PBN neurons revealed that MCAO resulted in an immediate decrease in the activity of PBN neurons, which was completely blocked after systemic estrogen injection. These results suggest that estrogen is released into the PBN in response to MCAO and that the source of estrogen seems to be primarily caused by terminal release as opposed to increased local synthesis.

Pathophysiology of Acute Ischaemic Stroke: An Analysis of Common Signalling Mechanisms and Identification of New Molecular Targets

Stroke continues to be a major cause of death and disability. The currently available therapies have proven to be highly unsatisfactory (except thrombolysis) and attempts are being made to identify and characterize signalling proteins which could be exploited to design novel therapeutic modalities. The pathophysiology of stroke is a complex process. Delaying interventions from the first hours to days or even weeks following blood vessel occlusion may lead to worsening or impairment of recovery in later stages. The objective of this review is to critically evaluate the major mechanisms underlying stroke pathophysiology, especially the role of cell signalling in excitotoxicity, inflammation, apoptosis, neuroprotection and angiogenesis, and highlight potential novel targets for drug discovery.

Changes in neuropeptide Y protein expression following photothrombotic brain infarction and epileptogenesis

This study characterized morphological changes in the cortex and hippocampus of Sprague-Dawley rats following photothrombotic infarction and epileptogenesis with emphasis on the distribution of neuropeptide Y (NPY) expression. Animals were lesioned in the left sensorimotor cortex and compared with age-matched naive and sham-operated controls by immunohistochemical techniques at 1, 3, 7, and 180 days post-lesioning (DPL). NPY immunostaining was assessed by light microscopy and quantified by the optical fractionator technique using unbiased stereological methods. At 1, 3, and 7 DPL, the number of NPY-positive somata in the lesioned cortex was increased significantly compared to controls and the contralateral cortex. At 180 DPL, lesioned epileptic animals with frequent seizure activity demonstrated significant increases of NPY expression in the cortex, CA1, CA3, hilar interneurons, and granule cells of the dentate gyrus. In addition to NPY immunostaining, neuronal degeneration, cell death/cell loss, and astroglial response were assessed with cell-specific markers. Nissl and NeuN staining showed reproducible infarctions at each investigated time point. FJB-positive somata were most abundant in the infarct core at 1 DPL, decreased markedly at 3 DPL, and virtually absent by 7 DPL. Activated astroglia were detected in the cortex and hippocampus following lesioning and the development of seizure activity. In summary, NPY protein expression and morphological changes following cortical photothrombosis were time-, region-, and pathologic state-dependent. Alterations in NPY expression may reflect reactive or compensatory responses of the rat brain to acute infarction and to the development and expression of epileptic seizures.

Estradiol increases brain lesions in the cortex and lateral striatum after transient occlusion of the middle cerebral artery in rats: no effect of ischemia on galanin in the stroke area but decreased levels in the hippocampus

A distinctive feature of galanin expression is that it is extensively increased by neuronal injury, estrogens, Alzheimer's disease and during development. Since stroke is amongst the clinically most important causes of neuronal injury we studied the tissue concentrations of galanin in a rat stroke model and the possibility of modulating this effect with estrogen. Transient focal middle cerebral artery ischemia was induced in rats that 2 weeks earlier underwent ovariectomy and received 1.5mg 17beta-estradiol slow-release or placebo pellets. The concentrations of galanin and neuropeptide Y were measured after observation periods of 3, 7 and 14 days in extracts of punch biopsies from both the lesioned and the contra lateral control hemisphere. The galanin levels were not changed in any of the brain regions studied except in the hippocampus where they were lower in the ischemic hemisphere in both the estrogen- and placebo-treated animals compared to the corresponding contra lateral intact hemisphere (p=0.015). Estrogen treatment up-regulated galanin concentrations in both the ventral and dorsal hippocampus (p=0.003). The effects on the galanin concentrations were similar after all observation periods: 3, 7 and 14 days (p=0.144). No significant changes were observed in the concentration of neuropeptide Y in response to the lesions. The ischemic lesions were markedly larger in the estrogen-treated animals observed after 3 days compared to the corresponding control group. In the estrogen group the lesion was largest at bregma and the slice 2mm anterior to the bregma, 82% and 435% larger than in the control group (p<0.001). A similar, but much less pronounced (not statistically significant) difference was seen in the groups observed after 7 and 14 days. Earlier studies of lesions in the peripheral and central nervous systems have generally shown an up-regulation of galanin markers in response to but at a distance from the injury. Our results indicate that galanin is not involved in the response of the ischemic penumbra itself to stroke, whereas it may participate in the reactions of the neural stem-cell rich hippocampus to stroke.

Neuropeptide Y-Y1 receptor agonist worsens while antagonist improves survival of cultured Y1-expressing neuronal cells following oxygen and glucose deprivation

In this in vitro study, we investigated the influence of neuropeptide Y (NPY) Y1 receptor activation or inhibition on the viability of cultured neuronal or glial cells following oxygen glucose deprivation (OGD). Viability of cultured cells was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. When compared to the vehicle-treated control group, treatment with NPY or [Leu31,Pro34]-NPY (Y1 agonist) reduced viability of cultured SK-N-MC (Y1-expressing) human neuronal cells at 24 h after 1 h of OGD, while BIBP3226 (Y1 antagonist) improved viability. Except at the highest concentration of NPY used in the study, treatment with NPY or NPY3-36 (Y2 agonist) did not influence viability of cultured SH-SY5Y (Y2-expressing) human neuronal cells at 24 h after 1 h of OGD. In addition, treatment with NPY, [Leu31,Pro34]-NPY, NPY3-36, or BIBP3226 did not affect viability of cultured primary astrocytes at 24 h after 4 h of OGD. The present results agree with those of a recent in vivo study. Activation of NPY-Y1 receptors may mediate ischemic pathophysiological processes, and inhibiting the Y1 receptors may be protective. The combination of OGD and cultured neuronal cells may be useful in future studies on the neuroprotective and harmful mechanisms of NPY-Y1 receptor inhibition and activation during ischemia, respectively.

Neuropeptide Y and its receptor analogs differentially modulate the immunoreactivity for neuronal or endothelial nitric oxide synthase in the rat brain following focal ischemia with reperfusion

An intracerebroventricular (i.c.v.) injection of neuropeptide Y (NPY) or [Leu31, Pro34]-NPY (non-Y2 receptor agonist) given during middle cerebral artery occlusion (MCAO) increases the infarct volume and nitric oxide (NO) overproduction in the rat brain. An i.c.v. injection of NPY3-36 (non-Y1 receptor agonist) has no effects, while BIBP3226 (selective Y1 receptor antagonist) reduces the infarct volume and NO overproduction. This study examined the effects of NPY or its receptor analog on the immunoreactivity (ir) for three isoforms of NO synthase (NOS) following 1 h of MCAO and 3 h of reperfusion. Focal ischemia/reperfusion led to increased ir for neuronal NOS (nNOS) within the ipsilateral caudate putamen and insular cortex. NPY or [Leu31, Pro34]-NPY enhanced but BIBP3226 suppressed such increase in the nNOS-ir. Focal ischemia/reperfusion also led to an ipsilateral increase in extent and/or intensity of the ir for endothelial NOS (eNOS) in the caudate putamen and/or parietal cortex. NPY or [Leu31, Pro34]-NPY suppressed but BIBP3226 enhanced such change in the eNOS-ir. NPY3-36 did not consistently influence the nNOS-ir or eNOS-ir following MCAO. Specific ir for inducible NOS was undetectable. These opposing effects of NPY-Y1 receptor activation or inhibition on nNOS and eNOS may lead to harmful or beneficial consequences following ischemia/reperfusion.

Estrogen synthesis in the central nucleus of the amygdala following middle cerebral artery occlusion: Role in modulating neurotransmission

Stroke-induced lesions of the insular cortex in the brain have been linked to autonomic dysfunction (sympathoexcitation) leading to arrhythmogenesis and sudden cardiac death. In experimental models, systemic estrogen administration in male rats has been shown to reduce stroke-induced cell death in the insular cortex as well as prevent sympathoexcitation. The central nucleus of the amygdala has been postulated to mediate sympathoexcitatory output from the insular cortex. We therefore set out to determine if endogenous estrogen levels within the central nucleus of the amygdala are altered following stroke and if microinjection of estrogen into the central nucleus of the amygdala modulates autonomic tone. Plasma estrogen concentrations were not altered by middle cerebral artery occlusion (22.86+/-0.14 pg/ml vs. 21.24+/-0.33 pg/ml; P>0.05). In contrast, estrogen concentrations in the central nucleus of the amygdala increased significantly following middle cerebral artery occlusion (from 20.83+/-0.54 pg/ml to 76.67+/-1.59 pg/ml; P<0.05). Local infusion of an aromatase inhibitor, letrozole, into the central nucleus of the amygdala at the time of middle cerebral artery occlusion prevented the increase in estrogen concentration suggesting that this increase was dependent on aromatization from testosterone. Furthermore, bilateral microinjection of estrogen (0.5 microM in 200 nl) directly into the central nucleus of the amygdala significantly decreased arterial pressure and sympathetic tone and increased baroreflex sensitivity, and these effects were enhanced following co-injection with either an N-methyl-D-aspartate or non-N-methyl-D-aspartate receptor antagonist. Taken together, the results suggest that middle cerebral artery occlusion resulted in synthesis of estrogen within the central nucleus of the amygdala and that this enhanced estrogen level may act to attenuate overstimulation of central nucleus of the amygdala neurons to prevent middle cerebral artery occlusion-induced autonomic dysfunction.

Estrogen attenuates neuronal excitability in the insular cortex following middle cerebral artery occlusion

The current investigation examined the role of estrogen in the insular cortex (IC) under both normal and ischemic conditions. Experiments were done in anaesthetized male Sprague-Dawley rats. The effect of systemic 17beta-estradiol (estrogen) administration on levels of amino acids and of endogenous estrogen obtained by microdialysis and its effect on neuronal activity of cells located in the insular cortex were measured in the absence of, and following permanent occlusion of, the right middle cerebral artery (MCA). In normal rats, intravenous (i.v.) injection of estrogen resulted in a significant increase (greater than 25 spikes/bin) in the spontaneous activity of neurons located within the insular cortex, while there was a significant decrease in gamma-aminobutyric acid (GABA) levels measured in IC dialysate. Middle cerebral artery occlusion (MCAO) resulted in a biphasic response consisting of a transient increase in the extracellular concentration of glutamate, aspartate, and GABA, followed by sustained elevations in glutamate and aspartate, but reduced GABA levels 4 h post-MCAO. MCAO also resulted in a significant increase in neuronal activity in the IC (from 28 +/- 9 to 120 +/- 88 spikes/bin). This MCAO-induced excitation was completely blocked following the prior intravenous administration of estrogen. Systemic estrogen administration also resulted in a delay in the progression and decrease in the final infarct volume by approximately 56%. Taken together, these results suggest that under normal conditions, estrogen excites neurons in the insular cortex by decreasing GABA release (disinhibition) and it plays a role in attenuating the MCAO-induced excitability and death of these neurons.

Dynorphin A inhibits NMDA receptors through a pH-dependent mechanism

Dynorphin A (DynA), an endogenous agonist of kappa-opioid receptors, has also been reported to directly interact with the NMDA receptor. DynA inhibition of NMDA receptor function has been suggested to be involved in its neuroprotective action during ischemic and acidic conditions. However, the effect of external pH on DynA inhibition of the NMDA receptor has not been reported. Here, we show that DynA inhibition of the NMDA receptor is dependent on extracellular pH over the range of pH 6.7-8.3, and the inhibition by 10 microM DynA increases at low pH by three- to four-fold in hippocampal neurons and in Xenopus oocytes expressing NR1-1a/2B subunits. Molecular studies showed that the interacting site for DynA on the NMDA receptor is distinct from that of proton or redox sites. Peptide mapping demonstrated important contributions of positively charged residues and specific structural organization of the peptide to the potency of DynA inhibition. Thus, DynA inhibits NMDA receptors through an allosteric mechanism, which is pH dependent and involves the specific structural features of the peptide.

Intracerebroventricular injection of a neuropeptide Y-Y1 receptor agonist increases while BIBP3226, a Y1 antagonist, reduces the infarct volume following transient middle cerebral artery occlusion in rats

Recent studies using middle cerebral artery occlusion in the rat have suggested a role of neuropeptide Y in ischemic pathophysiology. In this study, we investigated the effects of an i.c.v. injection of a neuropeptide Y-Y2 receptor agonist, neuropeptide Y 3-36, a Y1 receptor agonist, [Leu(31),Pro(34)]-neuropeptide Y, or a Y1 receptor antagonist, BIBP3226, on infarct volume and hemodynamic parameters following middle cerebral artery occlusion. Adult male Sprague-Dawley rats were subjected to transient middle cerebral artery occlusion for 2 h. A single i.c.v. injection of neuropeptide Y 3-36 (15 microg/kg), [Leu(31),Pro(34)]-neuropeptide Y (30 microg/kg), or BIBP3226 (5, 15, or 45 microg/kg) was given at 30 min of ischemia. Blood pressure, heart rate, and regional cerebral perfusion were monitored during ischemia and reperfusion. The rats were decapitated after 70 h of reperfusion, and their brains were cut into 2-mm-thick coronal slices before reaction with a 2% solution of 2,3,5-triphenyltetrazolium chloride to reveal the infarct. When compared with an infarct volume of 17.4+/-4.4% of the ipsilateral hemisphere following injection of neuropeptide Y 3-36, administration of the Y1 receptor analogs significantly modified the infarct volume (ordinary one-way analysis of variance (ANOVA), P<0.0001). [Leu(31),Pro(34)]-neuropeptide Y increased the infarct volume to 32.0+/-4.1% (Student-Newman-Keuls post-test, P<0.01), whereas BIBP3226 at 15 microg/kg decreased the infarct volume to 6.5+/-1.0% (post-test P<0.05). Although there was no major difference in the hemodynamic parameters among the groups, injection of [Leu(31),Pro(34)]-neuropeptide Y tended to further reduce cerebral perfusion during ischemia, while injection of BIBP3226 at 15 microg/kg appeared to have the opposite effect. In addition to glutamate, calcium ion and nitric oxide, activation of the neuropeptide Y-Y1 receptors may mediate cerebral damage during focal ischemia. Conversely, inhibiting the Y1 receptors may protect the brain against ischemic injury. Further studies are warranted to confirm the neuroprotective potential of neuropeptide Y-Y1 receptor inhibition.

Suppression of BDNF-induced expression of neuropeptide Y (NPY) in cortical cultures by oxygen-glucose deprivation: a model system to study ischemic mechanisms in the perinatal brain

The aim of this study was to establish a culture system that can serve as a model to study hypoxic-ischemic mechanisms regulating the functional expression of NPY neurons in the perinatal brain. Using an aggregate culture system derived from the rat fetal cortex, we defined the effects of oxygen and glucose deprivation on NPY expression, using BDNF-induced production of NPY as a functional criterion. NPY neurons exhibited a differential susceptibility to oxygen and glucose deprivation. Although the neurons could withstand oxygen deprivation for 16 hr, they were dramatically damaged by 8 hr of glucose deprivation and by 1-4 hr of deprivation of both oxygen and glucose (N+Glu-). One-hour exposure to N+Glu- led to a transient inhibition ( approximately 50%) of NPY production manifesting within 24 hr and recovering by 5 days thereafter, a 2-hr exposure to N+Glu- led to a sustained inhibition (50-75%) manifesting 1-5 days thereafter, and a 4-hr exposure to N+Glu- led to a total irreversible suppression of BDNF-induced production of NPY manifesting within 24 hr and lasting 8 days after re-supply of oxygen and glucose. Moreover, 1-hr exposure to N+Glu- led to a substantial and 4-hr exposure led to a total disappearance of immunostaining for MAP-2 and NPY but not for GFAP; indicating that neurons are the primary cell-type damaged by oxygen-glucose deprivation. Analysis of cell viability (LDH, MTT) indicated that progressive changes in cell integrity take place during the 4-hr exposure to N+Glu- followed by massive cell death 24 hr thereafter. Thus, we defined a culture system that can serve as a model to study mechanisms by which ischemic insult leads to suppression and eventually death of NPY neurons. Importantly, changes in NPY neurons can be integrated into the overall scheme of ischemic injury in the perinatal brain.

Neuropeptide Y-Y1 receptor modulates nitric oxide level during stroke in the rat

In a rat endovascular middle cerebral artery occlusion (MCAO) stroke model, we previously showed that intracerebroventricular (ICV) injection of neuropeptide Y (NPY) or an Y1 receptor agonist, [Leu(31),Pro(34)]-NPY, increased the infarct volume, that an Y1 receptor antagonist, BIBP3226, reduced the infarct volume, and that an Y2 receptor agonist, NPY3-36, had no effect. In this study, we used electron paramagnetic resonance (EPR) spectroscopy to measure nitric oxide (NO) and examined how ICV administration of NPY or its receptor analogs would modulate the brain NO level between the bregma levels +2 and -4 mm during MCAO, since excessive NO mediates ischemic damage. The relative brain NO concentration was increased to 131.94 +/- 7.99% (mean +/- SEM; n = 8) at 15 min of MCAO. NPY treatment further increased the relative brain NO concentration to 250.94 +/- 50.48% (n = 8), whereas BIBP3226 significantly reduced the brain NO concentration to 69.63 +/- 8.84% (n = 8). [Leu(31),Pro(34)]-NPY (137.61 +/- 14.54%; n = 7) or NPY3-36 (129.23 +/- 21.77%; n = 8) did not affect the brain NO concentration at 15 min of MCAO. Our results suggest that the NPY-Y1 receptor activation mediates ischemic injury via NO overproduction and that inhibition of the Y1 receptor may confer protection via suppression of excessive NO production during ischemia.

Peripheral and central administration of neuropeptide Y in a rat middle cerebral artery occlusion stroke model reduces cerebral blood flow and increases infarct volume

Recent studies have shown increased immunoreactivity for neuropeptide Y (NPY) within the perilesional cortex following experimental middle cerebral artery occlusion (MCAO) or focal excitotoxic damage. Downregulation of the NPY Y1 receptor gene using an antisense oligodeoxynucleotide produced a doubling of the infarct volume, implying that NPY may mediate neuroprotection against focal ischemia. The effects of treatment with NPY on infarct volume and hemodynamic parameters were investigated in the present study. Adult male Sprague-Dawley rats were anesthetized with sodium pentobarbital to undergo right-sided endovascular MCAO for 2 h. A single dose of NPY was given via intracarotid injection (10 microg/kg) at the beginning of reperfusion, intracisternal injection (10 or 30 microg/kg) at 30 min of ischemia, or intracerebroventricular (i.c.v.) injection (10 or 70 microg/kg) at 30 min of ischemia. Control groups received the vehicle only via the same route. Body temperature was maintained constant, and hemodynamic parameters were monitored during anesthesia. Laser Doppler flowmetry was used to monitor the regional cerebral blood flow (rCBF) during ischemia and reperfusion in some rats. The rats were decapitated on day 3, and their brains were cut into 2-mm thick coronal slices before reaction with a 2% solution of 2,3,5-triphenyltetrazolium chloride to reveal the infarct. Compared to the respective control groups, NPY treatment via any method of administration increased the relative infarct volume. Suppression of rCBF was observed during reperfusion. These results indicate that peripheral or central administration of NPY impairs reperfusion following experimental MCAO and worsens the outcome of focal cerebral ischemia.

Reduction in infarct size by local estrogen does not prevent autonomic dysfunction after stroke

Systemic estrogen administration in male rats has been shown to normalize the autonomic dysfunction and reduce the infarct size after permanent middle cerebral artery occlusion (MCAO). Therefore, the present investigation determined if local microinjection of estrogen at the site of the infarct also promoted recovery of autonomic function and reduction of the infarct size. Experiments were done in anesthetized (thiobutabarbitol sodium; 100 mg/kg) male Sprague-Dawley rats instrumented to record baseline and reflex changes in cardiovascular and autonomic parameters. The right middle cerebral artery was permanently occluded using bipolar coagulation. Local microinjection of estrogen into the insular cortex before MCAO significantly reduced the infarct size but did not attenuate the MCAO-induced autonomic dysfunction. Injection of ICI-182,780 alone significantly increased infarct area; however, the greater infarct area was not associated with enhanced autonomic dysfunction. These results suggest that within the insula, endogenous estrogen activity can affect the extent of MCAO-induced cell death, but extracortical central nervous system sites may be responsible for mediating the beneficial effects of estrogen on the autonomic disturbances.

Interleukin-1beta induces expression of neuropeptide Y in primary astrocyte cultures in a cytokine-specific manner: induction in human but not rat astrocytes

Previous studies have demonstrated that astrocyte cultures express neuropeptide Y (NPY) in a regulated manner, namely, phorbol ester leads to an increase in proNPY-mRNA and NPY production. In this respect, the behavior of astrocytes derived from the human fetal or rat neonatal brain is similar (Regul. Pept. 75 (1998) 293). Since astrocytes can be exposed to high levels of IL-1beta, we addressed the question: Does IL-1beta regulate NPY expression by the astrocytes? Primary astrocytes derived from the human fetal or rat neonatal cortex were cultured in serum-free medium. IL-1beta, but not IL-6 or TNF-alpha, led to an increase in NPY production dose-dependently. IL-1beta action manifested in the human but not in the rat astrocytes and it was completely abolished by IL-1 receptor antagonist. The responsiveness to IL-1beta did not diminish upon sub-culture of the astrocytes (five passages). In addition, IL-1beta led to an increase in the abundance of proNPY-mRNA, which was preceded by a rapid and transient increase in cFos-mRNA and a rapid and sustained increase in JunB-mRNA. In contrast to cFos/JunB, IL-1beta did not alter the abundance of cJun-mRNA. In summary, we demonstrate that IL-1beta induction of NPY expression in astrocytes is species- and cytokine-specific and that IL-1 receptor is involved. Moreover, induction of NPY expression is preceded by a rapid increase in the expression of two transcription factors (cFos, JunB) that have been previously (Oncogene 9 (1994) 2369; J. Neurochem. 70 (1998) 1887) implicated in transcriptional regulation of the human NPY gene.

Neuropeptide Y-Y1 receptor antisense oligodeoxynucleotide increases the infarct volume after middle cerebral artery occlusion in rats

An antisense oligodeoxynucleotide selective for the rat neuropeptide Y1 receptor gene was given into the left lateral ventricle in the experimental group of rats, whereas a missense oligodeoxynucleotide or saline was given in the control groups. Some rats were decapitated at 1-2h after the last injection of the oligodeoxynucleotides to examine their effects on the Y1 receptor density in the insular cortex. When compared to the Y1 and Y2 binding density of the untreated rats, the antisense-treated rats had reduced Y1 binding in the insular cortex but the Y2 binding was unaffected; treatment with missense oligodeoxynucleotide had no effect. Other rats underwent a right-sided middle cerebral artery occlusion at 1-2h after the last injection of the oligodeoxynucleotides or saline to examine the effect on the infarction volume at three days following stroke. The antisense treatment resulted in a doubling of the mean infarction volume when compared to the missense or saline treatment.Thus, reducing the Y1 receptor density prior to middle cerebral artery occlusion is harmful. Neuropeptide Y may mediate neuroprotection against focal ischemia via the cortical Y1 receptor, since the immunoreactivity for neuropeptide Y has been shown to increase within the peri-infarct cortex after middle cerebral artery occlusion.

Expression of neuropeptide Y receptors mRNA and protein in human brain vessels and cerebromicrovascular cells in culture

Neuropeptide Y (NPY) has been suggested as an important regulator of CBF. However, except for the presence of Y1 receptors in large cerebral arteries, little is known about its possible sites of action on brain vessels. In this study, we sought to identify the NPY receptors present in the human cerebrovascular bed. Specific Y1 receptor binding sites, localized on the smooth muscle of human pial vessels and potently competed by NPY, polypeptide YY (PYY), and the selective Y1 receptor antagonist BIBP 3226, were identified by quantitative radioautography of the Y1 radioligand [125I]-[Leu31, Pro34]-PYY. In contrast, no specific binding of the Y2-([125I]-PYY3-36) and Y4/Y5-(125I-human pancreatic polypeptide [hPP]) radioligands could be detected. By in situ hybridization, expression of Y1 receptor mRNA was restricted to the smooth muscle layer of pial vessels, whereas no specific signals were detected for either Y2, Y4, or Y5 receptors. Similarly, using reverse transcriptase-polymerase chain reaction (RT-PCR), mRNA for Y1 but not Y2, Y4, or Y5 receptors was consistently detected in isolated human pial vessels, intracortical microvessels, and capillaries. In human brain microvascular cells in culture, PCR products for the Y1 receptors were exclusively found in the smooth muscle cells. In cultures of human brain astrocytes, a cell type that associates intimately with brain microvessels, PCR products for Y1, Y2, and Y4 but not Y5 receptors were identified. Finally, NPY significantly inhibited the forskolin-induced cAMP production in smooth muscle but not in endothelial cell cultures. We conclude that smooth muscle Y1 receptors are the primary if not exclusive NPY receptors associated with human brain extraparenchymal and intraparenchymal blood vessels, where they most likely mediate cerebral vasoconstriction.

Evidence for the involvement of corticotrophin-releasing hormone in the pathogenesis of traumatic brain injury

The aim of this study was to investigate the role of the neuropeptide corticotrophin-releasing hormone (CRH) in neurodegeneration induced by traumatic brain injury, using a well characterized model of lateral fluid percussion injury in male, Sprague-Dawley rats. In the first series of experiments, CRH gene expression was assessed by in situ hybridization after traumatic brain injury. A bilateral increase in CRH mRNA in the paraventricular nucleus was observed in rats subjected to traumatic brain injury compared with sham-operated controls. A maximal (40%) increase in hybridization signal was detected 2 h after trauma compared with control rat brains. In addition, marked induction of CRH transcripts was found in the ipsilateral amygdala after trauma, but no increase was detected in the ipsilateral cortex around the area of damage. In a separate experiment, the effects of the CRH antagonist, D-Phe CRH(12-41) (25 microg total dose), or appropriate vehicle injected intracerebroventricularly, was tested on infarct volume caused by brain injury. Repeated intracerebroventricular injection of D-Phe CRH(12-41) significantly reduced, by 45%, the volume of cortical damage in injured rats compared with vehicle-treated, trauma animals. The rapid upregulation of CRH gene expression in the paraventricular nucleus and amygdala following lateral fluid percussion injury and the marked neuroprotection achieved by inhibiting CRH action suggest that CRH is involved directly in the pathogenesis of traumatic brain injury. This observation may have important implications for the development of novel therapeutic strategies for treating the neurological consequences of brain trauma and related conditions.

Cardiovascular response to stress after middle cerebral artery occlusion in rats

Previously, we have shown cardiovascular and autonomic disturbances in male Wistar rats following middle cerebral artery occlusion (MCAO). Using this model, neurochemical changes, that were maximal at 3-5 days and subsiding by day 10, were observed unilaterally in the insular cortex and amygdala. The amygdalar neurochemical changes may be related to the stroke-induced cardiovascular disturbances, since the amygdala is critical in mediating the cardiovascular responses to stress. We examined the cardiovascular responses to intermittent and continuous noise and air-jet stimulation in male Wistar rats on days 2-10 after right-sided MCAO or sham MCAO. Compared to the sham MCAO rats, intermittent noise elicited significant tachycardiac responses on days 5 and 7 after stroke. Air-jet stimulation also elicited a significant tachycardic response on day 5, whereas continuous noise produced significant tachycardiac and pressor responses at days 5 and 7, respectively, in the MCAO rats compared to the control rats. Analyses on the heart rate variability using fast Fourier transformation revealed significant increases in the normalized mid-frequency spectral power on day 7 for intermittent noise and air-jet stimulation, suggesting increases in the sympathetic activity. These results indicate a time-course of exaggerated cardiovascular responses to stress and suggest a state of susceptibility to cardiac perturbations in rats following stroke.

Endogenous opiates: 1995

This article is the eighteenth installment of our annual review of research concerning the opiate system. It includes articles published during 1995 reporting the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects. The specific topics covered this year include stress: tolerance and dependence; eating; drinking; gastrointestinal, renal, and hepatic function; mental illness and mood; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; sex, pregnancy, and development; immunological responses; and other behaviors.

Neuropeptide changes following excitotoxic lesion of the insular cortex in rats

Following middle cerebral artery occlusion in Wistar rats, the immunoreactivity of neuropeptide Y increased ipsilaterally in the insular cortex and basolateral nucleus of the amygdala. In addition, the immunoreactivity of leucine-enkephalin, dynorphin, and neurotensin increased in the ipsilateral central nucleus of the amygdala. The amygdalar neurochemical changes are likely the result of damage to the insular cortex, although other cortical areas were also affected by the ischemia. To investigate whether damage to the insular cortex is essential in eliciting these changes, a localized lesion of the right or left insular cortex was produced by microinjection of D,L-homocysteic acid. Control animals received injections of vehicle into the right or left insular cortex or D,L-homocysteic acid into the right primary somatosensory cortex. Neurochemical changes were examined immunohistochemically with the peroxidase-antiperoxidase reaction 5 days after the injection. The immunoreactivity of neuropeptide Y increased locally after excitotoxic damage to the insular cortex or primary somatosensory cortex. The amygdalar neurochemical changes, including neuropeptide Y increase in the basolateral nucleus and leucine-enkephalin, dynorphin, and neurotensin increase in the central nucleus, were seen only when the ipsilateral insular cortex was lesioned. These neurochemical changes were similar to those seen 5 days after middle cerebral artery occlusion. Our findings indicate that damage to the insular cortex is essential in eliciting the neurochemical changes in the ipsilateral amygdala. In addition, the change in neuropeptide Y in the cortex appears to be a local reaction occurring irrespective of location of the lesion and glutamate receptor activation may be involved.