[Effects of doxepin on isolated basilar and saphenous artery rings of rabbits]

AIM

To study the effects of doxepin (Dox) on cerebral artery.

METHODS

The effects of Dox were observed using the isolated basilar and saphenous artery rings of rabbits.

RESULTS

Dox inhibited the constriction of the basilar and saphenous artery rings evoked by KCl with IC50 5.75 mumol.L-1 (95% confidence limits were 2.3-14 mumol.L-1, n = 8) and 34.6 mumol.L-1 (95% confidence limits were 3.8-316 mumol.L-1, n = 8), respectively. Dox also inhibited the constriction of the basilar and saphenous artery rings of the rabbits stimulated by 5-hydroxytryptamine (5-HT), IC50 were 6.3 mumol.L-1 (95% confidence limits were 1.7-23.3 mumol.L-1, n = 7) and 8.0 mumol.L-1 (95% confidence limits were 6.3-10.3 mumol.L-1, n = 6), respectively. In both samples (basilar and saphenous artery rings) CaCl2 evoked, the pD2 of Dox was 5.28 +/- 0.40 and 4.76 +/- 0.14, respectively (n = 6, P < 0.01). Dox 5.8 mumol.L-1 inhibited the constriction of the saphenous artery evoked by norepinephrine (NE) in Ca(2+)-free medium. Dox 30 mumol.L-1 inhibited the constriction of the saphenous artery evoked both by NE and by readmission of CaCl2 (1.25 mmol.L-1).

CONCLUSION

As compared with its effect on the saphenous artery, Dox selectively inhibited the basilar artery.

The distal cytoplasmic domain of the erythropoietin receptor induces granulocytic differentiation in 32D cells

The role of hematopoietic growth factors in lineage commitment and differentiation is unclear. We present evidence that heterologous expression of an erythroid specific receptor allows granulocytic differentiation of a myeloid cell line. We have previously characterized a truncation mutant of the erythropoietin receptor (EpoR), which is associated with familial erythrocytosis (Blood 89:4628, 1997). This truncated EpoR lacks the distal 70 amino acids of the cytoplasmic domain. To study the functional role of this distal receptor domain, 32D cells, a murine interleukin-3 (IL-3)-dependent myeloid line, were transfected with the wild-type EpoR (32D/EpoR WT) or the truncated EpoR (32D/EpoR FE). 32D cells expressing either the full-length or truncated EpoR display equivalent proliferative rates in saturating concentrations of Epo. There is a dramatic difference in maturational phenotype between the two cell lines, however. The 32D/EpoR FE cells and mock transfected 32D cells have an immature, monoblastic morphology and do not express the primary granule protein myeloperoxidase. The 32D/EpoR WT cells, on the other hand, demonstrate granulocytic differentiation with profuse granulation, mature, clumped chromatin, and myeloperoxidase expression. There is no evidence of erythroid differentiation in 32D cells transfected with either the full-length or truncated EpoR. Treatment of the cells with the specific Jak2 inhibitor tyrphostin AG 490 inhibits myeloid differentiation driven by the distal EpoR. We conclude that: (1) the distal cytoplasmic domain of the EpoR is able to induce a specific myeloid differentiation signal distinct from mitogenic signaling, and (2) these data extend to myelopoiesis the growing body of evidence that the cellular milieu, not the specific cytokine receptor, determines the specificity of differentiation after cytokine receptor activation.

Functional characterization of a kindling-like model of ethanol withdrawal in cortical cultured neurons after chronic intermittent ethanol exposure

Chronic ethanol exposure has been reported to alter NMDA and GABA(A) receptor function and gene expression in brain regions of animals and mammalian cultured cortical neurons. In the present study, we investigated the effects of another model of chronic, but intermittent, ethanol treatment (CIE) on GABA(A) and NMDA receptor systems in cortical neurons. CIE (50 mM ethanol, 12 h exposure/12 h withdrawal, 5 cycles) exposure produced increased [3H]MK-801 binding and diazepam insensitive binding sites as measured by [3H]Ro15-4513 binding to cortical cultured neuronal membranes, at 0 h following the last treatment cycle relative to control neurons. The NMDA mediated increase in intracellular calcium [Ca2+]i was also increased following similar CIE treatment. CIE treatment also increased the ability of pentylenetetrazol (PTZ) to inhibit GABA mediated 36Cl- influx relative to control neurons. These effects were not reversible following 1 week ethanol withdrawal, implying enhanced sensitivity of PTZ to inhibit GABA(A) receptor mediated inhibition, and an increased NMDA receptor function in CIE treated cortical neurons. These alterations are consistent with the behavioral studies in animals, and suggest that both GABA(A) and NMDA receptors play an important role in ethanol withdrawal following either chronic or CIE exposure. Furthermore, this provides a feasible in vitro model for further biochemical and molecular studies of the mechanism underlying the CIE induced kindling-like phenomenon observed in humans.

[Changes of synaptic transmission efficiency in the MF-CA3 and PP-CA3 pathways of rat hippocampus during discrimination learning]

Electrophysiological and behavioral studies were performed in rat to investigate the changes of synaptic efficacy of the two inputs of hippocampal CA3 area [Mossy Fiber (MF) -CA3 and Perforant Path (PP) -CA3] during discrimination learning. The results showed that: (1) Amplitude of the population spike (PS) of both from MF-CA3 and PP-CA3 increased simultaneously with the establishment of conditioned response (CR) and both reached their maxima before CR reached the criterion of acquisition. (2) During natural extinction of CR, the amplitude of PS of both inputs decreased also simultaneously to their per-training level. These results indicated that the learning-dependent long-term potentiation (LTP) in both MF-CA3 and PP-CA3 inputs developed and extinguished synchronously, suggesting that the changes of synaptic efficacy of different inputs of hippocampal CA3 area coordinated during discrimination learning.

Plasma membrane calcium ATPase in synaptic terminals of chick Edinger-Westphal neurons

The plasma membrane calcium ATPase pump (PMCA) is one of two major mechanisms known to be involved in extruding calcium from cells. The monoclonal antibody 5F10 was used to examine the distribution of PMCA in chick Edinger-Westphal neurons, a population of cholinergic preganglionic neurons whose cells bodies reside in the Edinger-Westphal nucleus in the brainstem and whose axons form synaptic terminals on parasympathetic neurons in the ciliary ganglion. Definitive PMCA immunoreactivity was undetectable in Edinger-Westphal cell bodies in the brainstem. In contrast, immunoreactivity for PMCA was robust in ciliary ganglia and resembled patterns of immunoreactivity for the synaptic vesicle antigen SV-2, suggesting that PMCA is expressed in Edinger-Westphal synaptic terminals. Moreover, PMCA immunoreactivity co-localized with immunoreactivity for enkephalin and substance P, two neuropeptides known to be expressed in Edinger-Westphal synaptic terminals. Fine structure studies revealed that PMCA immunoreactivity is associated with synaptic vesicles rather than the plasma membrane in Edinger-Westphal terminals. In immunodot assays, synaptic vesicles purified from Torpedo electric organ are also immunoreactive for PMCA as well as SV-2. Torpedo vesicles are negative for the sarcoplasmic/ endoplasmic reticulum ATPase, suggesting that the observed PMCA immunoreactivity is not associated with smooth endoplasmic reticulum. Immunoblot analysis confirmed that 5F10 recognizes a protein with the correct molecular mass for PMCA in tissue homogenates of chick cerebellum, chick ciliary ganglia, and Torpedo synaptic vesicles. These findings describe a previously unrecognized location for PMCA in the membranes of cholinergic synaptic vesicles. Relevance to previous data and possible functions are discussed.

Morphological diversity in terminals of W-type retinal ganglion cells at projection sites in cat brain

The morphological features of retinal terminals in cat brain were examined at sites where projections of W-type ganglion cells predominate. These included the parvicellular C laminae of the dorsal lateral geniculate nucleus, the ventral lateral geniculate nucleus, stratum griseum superficiale of the superior colliculus, and the suprachiasmatic nucleus. Positive identification of retinal terminals was achieved following anterograde transport of intravitreally injected native or wheat germ agglutinin-conjugated horseradish peroxidase. In contrast to the classic features of retinal terminals as defined from sites where X- and Y-type ganglion cells predominate, i.e. round synaptic vesicles, large profiles, and pale mitochondria, substantial numbers of terminals in W-cell rich areas were found to contain dark mitochondria. Synaptic vesicles, although consistently round, were typically smaller in terminals with dark mitochondria than in those with pale mitochondria. These findings indicate a diversity among terminals of W-cells and suggest that such terminals cannot be distinguished on the basis of limited morphological criteria.

Chronic ethanol treatment produces a selective upregulation of the NMDA receptor subunit gene expression in mammalian cultured cortical neurons

Our previous work has shown that chronic ethanol treatment upregulated NMDA receptor function and binding in mammalian cortical neurons. However, the potential molecular mechanisms involved in these phenomenon have yet to be elucidated. In the present study, using RNase protection assay, we investigated the effect of chronic ethanol treatment on the NMDA receptor subunits R1, R2A, and R2B mRNA levels in cultured cortical neurons. We found that chronic ethanol (50 mM, 5 days) exposure did not change the NMDA receptor R1 and R2A subunits mRNA levels. In contrast, the NMDA receptor R2B subunit mRNA level was increased by approximately 40% with respect to the control values. The levels of the R2B subunit mRNA returned to the control values following the removal of ethanol for 72 h. In order to determine the involvement of the NMDA receptors in the action of chronic ethanol exposure, we further investigated the effect of the NMDA receptor antagonists on the upregulation induced by chronic ethanol exposure. The results indicate that the increased R2B subunit level was reversed by concomitant chronic exposure of the cortical neurons to the NMDA receptor competitive (10 microM; CPP), and non-competitive (1 microM; MK-801) antagonists, but not by the non-NMDA receptor antagonist, CNQX (10 microM), or the L-type calcium channel blocker, nitrendipine (10 microM). Taken together, these results suggested that chronic ethanol exposure selectively upregulated the NMDA receptor subunit R2B mRNA level in cortical neurons, and this increased NMDA receptor gene expression appears to be a NMDA receptor mediated process. The altered NMDA receptor gene expression may be responsible for the observed upregulation of the NMDA receptor binding and function in the cortical neurons following chronic ethanol exposure.

Chronic ethanol treatment upregulates the NMDA receptor function and binding in mammalian cortical neurons

In the present study, we investigated the effects of chronic ethanol exposure on NMDA-mediated increase in intracellular calcium concentration ([Ca2+]i) by means of fluorescent measurement of [Ca2+]i with Fura-2AM in mammalian cortical cultured neurons, and the radioligand [3H]MK-801 binding to cortical neuronal membranes. Chronic exposure of the cortical neurons to ethanol (50 mM, 5 days) did not produce any change in the cell protein, morphological appearance, and the resting [Ca2+]i; however, it significantly enhanced the NMDA-mediated increase in [Ca2+]i. The EC50 value of NMDA was not significantly altered following chronic ethanol exposure, however, its Emax value was increased by approximately 45%. Furthermore, chronic ethanol exposure increased the specific [3H]MK-801 binding in cortical neuronal membrane preparation by approximately 30%. The enhancement of the NMDA-mediated increase in [Ca2+]i and the increase in [3H]MK-801 specific binding were reversed following 48 h ethanol withdrawal. Additionally, this enhanced NMDA response and the increased [3H]MK-801 specific binding were susceptible to blockade by the concomitant chronic exposure of the cortical neurons to the NMDA receptor competitive (20 microM CPP), and non-competitive (1 microM MK-801) antagonists, but not by the non-NMDA receptor antagonist, CNQX (10 microM), and the L-type calcium channel blocker, nitrendipine (10 microM). Taken together, these results suggest that chronic ethanol exposure upregulated the NMDA receptor function and binding in cortical cultured neurons, and this increased NMDA receptor function is a NMDA receptor-mediated process. This altered NMDA receptor function may be responsible for the chronic ethanol-induced behavioral consequences and withdrawal syndrome associated with chronic ethanol exposure.

Neurological deficit and extent of neuronal necrosis attributable to middle cerebral artery occlusion in rats. Statistical validation

BACKGROUND AND PURPOSE

Occluding a large intracranial artery in rats produces a brain lesion that grows in terms of an increase in both surface area and number of necrotic neurons. The present study investigated whether reperfusing the ischemic territory 30 to 60 minutes after the arterial occlusion would have a beneficial effect on either the clinical or the histological outcome of the lesion.

METHODS

One hundred four adult rats (including appropriate controls) were used; 97 had a middle cerebral artery occluded by inserting a nylon monofilament via the right external carotid artery. The arterial occlusion was transient in two groups and permanent in another; survival times were comparable for all groups. Control animals were subjected to a sham operation during which the artery was occluded for less than 1 minute. The outcome was evaluated by measuring the extent of the neurological deficit and the severity of the histological injury.

RESULTS

Mean neurological score and mean number of necrotic neurons in the cortex were more favorable after transient (30- to 60-minute) compared with permanent arterial occlusion (P < .005). Moreover, the correlation between mean neurological score and mean number of necrotic neurons was highly significant: r = .951; P < .001.

CONCLUSIONS

The histological effects of an intracranial arterial occlusion in the adult rat can be predicted on day 1 by the neurological score described in this report. Significant improvement can be obtained in these animals by reestablishing arterial flow 60 minutes or sooner after the ictus. The pattern of cortical pannecrosis observed after permanent occlusion (> or = 72 hours) was transformed into incomplete ischemic injury in most instances of transient occlusion.

Morphological study of the rostral interstitial nucleus of the medial longitudinal fasciculus in the monkey, Macaca mulatta, by Nissl, Golgi, and computer reconstruction and rotation methods

We have studied the morphology of silver-impregnated neurons (rapid Golgi technique) in the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), a center involved in the control of vertical and torsional saccadic eye movements. This morphological study of riMLF neurons in the rhesus monkey was undertaken to further our understanding of the functional circuitry of the oculomotor system. Our study employed Nissl, Golgi, and computer-assisted methods. The cytoarchitectonic boundaries of the riMLF and its relationships to neighboring structures were determined in both Nissl and Golgi preparations. Five (I-V) distinct morphological types of riMLF neurons were distinguished in the Golgi impregnations on the basis of soma size, dendritic size, numbers of primary dendrites, number of dendritic branch points, as well as form, number, and distribution of dendritic appendages. Type I neurons impregnated most frequently and had the most extensive and highly branched dendritic tree. Type II neurons displayed thick dendrites with complex dendritic appendages, but the dendritic tree was much more compact than that of type I cells. Type III and type V cells had fusiform somas and relatively unbranched dendritic trees but differed greatly in size as well as dendritic morphology. The type IV cell was the smallest neuron and had many characteristics of the local interneurons found in other thalamic, subthalamic, hypothalamic and midbrain centers. The type V was the largest neuron, least frequently impregnated, and found only at rostral riMLF levels. Digitized reconstructions of each type of neuron were rotated by the computer, which revealed that the dendritic trees of types I, III, and V occupy a disk-like compartment in the riMLF neuropil. In contrast, the tree of types II and IV occupy a roughly spherical compartment. We suggest that three of the cell types are well suited for specific purposes: type II cells for receiving topographically organized inputs that contain spatial information, type I cells for short-lead burst neuron output to the motor neurons or other premotor centers, and type IV cells for inhibitory inputs to type I cells.

Chronic flurazepam treatment produces decreased efficacy of the benzodiazepine ligands and pentobarbital with gamma-aminobutyric acidA receptors in cortical neurons

The present study was designed to determine whether chronic benzodiazepine (BZ) agonist treatment alters the "set point" of the BZ pharmacological profile. This was achieved by investigating the modulation of gamma-aminobutyric acid (GABA)-mediated [36Cl-] influx by BZ ligands, as well as pentobarbital after chronic flurazepam treatment, in well characterized mammalian cortical neurons. Chronic flurazepam treatment (5 microM, 10 days) produced decreased efficacy of BZ agonists (diazepam and flunitrazepam) and inverse agonists (methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3'-carboxylate and ethyl-beta-carboline-3-carboxylate), as measured by GABA-induced [36Cl-] influx. The chronic flurazepam treatment, although not altering their EC50/IC50 values, decreased the Emax/-Emax values. Furthermore, the decreased efficacy was reversed after a 72-hr withdrawal, and by concomitant exposure of the neurons to Ro15-1788 (ethyl-8-fluoro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5 alpha][1,4]- BZ-3-carboxylate), a BZ receptor antagonist, but not by R 5135 (3 alpha-hydroxy-16-imino-5 beta-17-androstan-11-one; a GABA receptor antagonist) and pircrotoxin (a channel blocker). The chronic flurazepam treatment also produced uncoupling between pentobarbital and BZ receptor sites, and decreased the efficacy of pentobarbital to enhance GABA-mediated [36Cl-] influx, events also reversed at 72-hr withdrawal and concomitant exposure to Ro15-1788. Chronic flurazepam treatment-induced uncoupling and decreased efficacy of BZ agonists was not reversed by the GABAA receptor antagonist, R 5135, or channel blocker, picrotoxin.(ABSTRACT TRUNCATED AT 250 WORDS)

Development pattern of the GABAA-benzodiazepine receptor ionophore complex in primary cultures of cortical neurons

The development pattern of the GABAA/benzodiazepine (BZ) receptor ionophore complex was characterized in mammalian cortical cultured neurons utilizing radioligand binding and GABA-induced 36Cl-influx. The specific binding of [3H]flunitrazepam, [3H]Ro15-1788 and [3H]Ro15-4513 increased with time from day 3 to day 21. The EC50 value and Emax of the GABA, muscimol and pentobarbital to enhance [3H]-flunitrazepam binding did not change during the development. Furthermore, GABA-induced 36Cl- influx also did not change during development from day 3 to day 21. However, the potency of ligands that bind to type-1 BZ receptors (alprazolam, zolpidem and C1218,872) to inhibit [3H]flunitrazepam binding increased from day 7 to day 21. Taken together, these data suggest the presence of type-II BZ receptors in early stages of the development which appears to change to type-I BZ receptors with age in the cortical neurons in culture.

Chronic benzodiazepine agonist treatment produces functional uncoupling of the gamma-aminobutyric acid-benzodiazepine receptor ionophore complex in cortical neurons

We have investigated the effect of chronic flurazepam HCl treatment on the gamma-aminobutyric acid (GABA)A receptor complex in cultured mammalian cortical neurons. Chronic flurazepam (1-5 microM, for 1-10 days) treatment did not produce any changes in the morphological appearance or the cell protein content of cortical neurons. The basal binding of [3H]flunitrazepam, [3H] Ro15-1788, and [3H]Ro15-4513 was also not altered after the chronic treatment. However, chronic flurazepam treatment produced uncoupling between GABA and pentobarbital sites and the [3H]flunitrazepam binding site. The EC50 values of GABA and pentobarbital were not significantly altered after chronic flurazepam treatment; however, their Emax values were decreased by approximately 50%. The effect of chronic flurazepam treatment on the observed uncoupling was both time and concentration dependent. Furthermore, the binding of [3H]GABA and t-butylbicyclophosphoro[35S]thionate was also not altered by chronic flurazepam treatment. The effect of GABA on 36Cl influx was not altered after chronic flurazepam treatment; however, treatment significantly attenuated the ability of diazepam to enhance GABA-induced 36Cl influx. Chronic flurazepam-induced uncoupling and decreased diazepam efficacy were reversed by the concomitant presence of the benzodiazepine antagonist Ro15-1788, suggesting that these events are mediated via the benzodiazepine receptor site. Taken together, these results suggest that chronic benzodiazepine treatment produces uncoupling of GABA and pentobarbital sites from the benzodiazepine site and decreased coupling between the benzodiazepine site and GABA receptor-gated Cl- channels. The uncoupling and decreased efficacy may be due to an alteration in the levels of various alpha subunits and may be responsible for the tolerance associated with chronic benzodiazepine agonist treatment.

Organization of the zona incerta in the macaque: a Nissl and Golgi study

The zona incerta has been implicated in the control of the initiation of saccadic eye movements in the primate. Complex interactions within the zona incerta must take place to integrate its varied inputs and to produce a coherent efferent signal in order for this function to occur. However, whether the anatomical substrates exist within the zona incerta to allow this integration to take place has not been established. The zona incerta in monkeys (Macaca mulatta) was examined in frontally, horizontally, and sagittally sectioned preparations stained for Nissl, myelinated fibers, or cytochrome oxidase, or impregnated by the Golgi technique. This nucleus can be separated into dorsal and ventral laminae on the basis of staining and morphological differences between these two subdivisions. Neurons are more densely packed, more darkly stained, and larger in the ventral lamina. In addition, the neuropil of the ventral lamina is much more intensely stained after cytochrome oxidase histochemistry. Two neuronal types, principal cells and interneurons, were identified on the basis of neuronal cell body, dendritic, and axonal features in Golgi-impregnated preparations. Principal cells have fusiform or polygonal somata (long axis from 18 to 40 microns) and dendrites that extend for up to 750 microns within the lamina in which the cell bodies are located. Putative local interneurons have small (12-16 microns), round or oval cell bodies with wavy dendrites (up to 400 microns). Numerous multilobed appendages and axon-like processes originate from these dendrites and make apparent contacts with other interneurons or with dendrites of principal cells. Dendrites of most neurons in both laminae are oriented preferentially along the principal axis, dorsolateral-to-ventromedial, of the nucleus. Therefore, within the limits of light microscopy, the zona incerta appears to possess the morphological heterogeneity to form complex intrinsic interactions. These interactions are hypothesized to form the integrative substrate for the large array of incertal inputs that are utilized to produce an efferent signal involved in the initiation of saccadic eye movements.

Choice of lasers for laser angioplasty

Thrombi in test-tube, intraarterial thrombi and pig aorta wall were in vitro irradiated with continuous CO2 laser, short pulsal and ultrashort pulsal YAG laser (with pulse-width of 10 ns and 40 ps, respectively) and their double frequency laser and excimer laser with a wave-length of 308 nm and pulse-width of 20 ns. Their effect of vaporizing and ablating (photodecomposing) thrombi and their thermal injuring effect on adjacent tissues were compared and assessed in order to select optimal laser with little thermal injuring and more rapid vaporizing or ablating thrombi effect for laser angioplasty. The experimental results showed that excimer laser, ultrashort pulsal YAG laser and its double frequency laser, and double frequency laser of short pulsal YAG laser, with laser beam and blood vessel kept in a coaxial position, can effectively vaporize or ablate thrombi without thermal injury to vessel wall. So they may be used for laser angioplasty. Of them, especially, excimer laser and double frequency laser of ultrashort pulsal YAG laser have short wave-length and high peak power, and more effectively ablate thrombi than others, so they proved to be optimal lasers for laser angioplasty.