Synthesis and antibacterial activity of 2-aryl-2,5-dihydro-3(3H)-oxo-pyridazino[4,3-b]indole-4-carboxylic acids

The in vitro antibacterial and antifungal activities of a series of pyridazinoindolonic acids II against some selected representative of Gram-positive, Gram-negative bacteria and fungi have been investigated. Some interesting observations among the structural features necessary for high antibacterial activity are presented and discussed.

The homing pigeon hippocampus and the development of landmark navigation

The role of the homing pigeon hippocampal formation was examined in the development of loft fidelity and landmark navigation. During the course of five summers, different groups of young pigeons (hippocampal-lesioned, control-lesioned, and unoperated controls) were given free flight experience followed by short distance training and experimental releases. In Experiment 1, a census of which loft each pigeon entered revealed that hippocampal lesioned pigeons displayed less loft fidelity than controls. In Experiment 2 and 3, the percent of young birds lost during their first summer of training and their first experimental release was examined. Despite displaying similarly good homeward-oriented vanishing bearings, significantly more hippocampal lesioned pigeons were lost compared to control groups. The results support the hypothesis that the homing pigeon hippocampal formation participates in the learning/operation of a spatial representation of local landmarks near the loft that can be used for loft recognition and navigation.

Postnatal development of parvalbumin immunoreactive amacrine cells in the rabbit retina

In the adult rabbit, rat and cat retina, parvalbumin (PV) immunoreactivity is primarily localized to a population of narrow-field, bistratified amacrine cells, the AII amacrine cells-major interneurons of the rod pathway. This investigation examines the postnatal development of PV immunoreactivity in order to better understand the ontogeny of the AII amacrine cell population and the formation of the rod pathway. Rabbit retinas at various postnatal ages were processed for immunohistochemistry using a monoclonal antibody directed to PV and analyzed morphometrically. On the day of birth, PV immunoreactive cell bodies are numerous in the proximal inner nuclear layer (INL) in all retinal regions. These cells have a primary process directed towards the inner plexiform layer (IPL). At postnatal day (PND) 2, a few faint immunoreactive processes are observed in the IPL. At PND 4, well-stained processes are observed to ramify mainly in the proximal IPL. At PND 6, strongly immunoreactive processes are present in both the distal and proximal IPL, and at PND 10 they form a continuous, dense plexus in both levels of the IPL. By PND 10, the morphology of PV immunoreactive cells is similar to PV immunoreactive cells in adult retinas. The density of PV immunoreactive cells in the proximal INL increases from PND 2 to PND 5, then it gradually decreases to adult values, while the total number of PV immunoreactive cell bodies increases until PND 10. PV immunoreactive amacrine cells at PND 2, as in the adult, are nonrandomly distributed across the retinal surface. These studies show that PV immunoreactive amacrine cells have a developmental profile that is similar to several other amacrine cell types. This includes the elaboration of processes in the IPL during the first postnatal week and a mature appearance towards the end of the second week of life, about the time of eye opening. These observations indicate that the AII amacrine cell may participate in the processing of visual information at eye opening.

Transient somatostatin-immunoreactive ganglion cells in the developing rat retina

The peptide somatostatin (SRIF) is likely to play important roles in neuronal differentiation and maturation. In the mammalian retina, it is reported to be expressed by populations of amacrine and/or displaced amacrine cells and, in some species, by some ganglion cells. Previous studies have shown that in the rat retina the maturation of somatostatinergic systems encompasses late prenatal and early postnatal periods, suggesting a role of SRIF in maturative events of the retina. SRIF-expressing ganglion cells have not been reported in the rat retina at any developmental age. In the present study, we re-evaluated the postnatal development of SRIF-containing neurons of the rat retina focusing on the analysis of SRIF-containing cells in the ganglion cell layer (GCL), to test the possibility that SRIF is expressed by some ganglion cells during development. To this aim we combined immunocytochemical staining of SRIF-positive neurons with retrograde tracing of ganglion cell bodies through Fluoro-Gold injections into the superior colliculus. Double-labelling experiments revealed the presence of SRIF-containing ganglion cells at postnatal day (PND) 10. They accounted for 14% of the total SRIF-containing cells in the GCL. Such double-labelled cells were not observed either before (PND 7) or after (PND 15 and PND 45) this period. This transient expression of SRIF in retinal ganglion cells suggests that SRIF may be a factor regulating the maturation of retinocollicular projections in a restricted period of postnatal development.

Morphologic maturation of tachykinin peptide-expressing cells in the postnatal rabbit retina

Tachykinin (TK) peptides, which include substance P, neurokinin A, two neurokinin A-related peptides and neurokinin B, are widely present in the nervous system, including the retina, where they act as neurotransmitters/modulators as well as growth factors. In the present study, we investigated the maturation of TK-immunoreactive (IR) cells in the rabbit retina with the aim of further contributing to the knowledge of the development of transmitter-identified retinal cell populations. In the adult retina, the pattern of TK immunostaining is consistent with the presence of TK peptides in amacrine, displaced amacrine, interplexiform and ganglion cells. In the newborn retina, intensely immunostained TK-IR somata are located in the ganglion cell layer (GCL) and in the inner nuclear layer (INL) adjacent to the inner plexiform layer (IPL). They are characterized by an oval-shaped cell body originating a single process without ramifications. TK-IR processes are occasionally observed in the IPL and in the outer plexiform layer (OPL). Long TK-IR fiber bundles are observed in the ganglion cell axon layer. TK-IR profiles resembling small somata are rarely observed in the INL adjacent to the OPL. At postnatal day (PND) 2, some TK-IR cells display more complex morphologic features, including processes with secondary ramifications. Long TK-IR processes in the IPL are often seen to terminate with growth cones. Between PND 6 and PND 11 (eye opening), there is a dramatic increase in the number of immunolabeled processes with growth cones both in the IPL and in the OPL and the mature lamination of TK-IR fibers in laminae 1, 3 and 5 of the IPL is established. TK-IR cells attain mature morphological characteristics and the rare, putative TK-IR somata in the distal INL are no longer observed. After eye opening, growth cones are not present and the pattern typical of the adult is reached. These observations indicate that the development of TK-IR cells can be divided into an early phase (from birth to PND 6) in which these cells establish their morphological characteristics, and a later phase (from PND 6 to eye opening) in which they are involved in active growth of their processes and likely in synapse formation. Since TK peptides are thought to play neurotrophic actions in the developing nervous system and they are consistently present in the retina throughout postnatal development, they may also act as growth factors during retinal maturation.

The neuroethology of cognitive maps: contributions from research on the hippocampus and homing pigeon navigation

The rich ethological tradition that characterizes the homing behavior of pigeons offers an excellent opportunity to examine the importance of the hippocampal formation for the regulation of spatial cognitive mechanisms. The present review summarizes both anatomical and behavioral data obtained in researches on the pigeon hippocampal formation that have been performed over the last 12 years. Pathway connection studies and investigations on the neurochemical organization of the avian hippocampal formation show that this structure shares many similarities with the mammalian hippocampus and provide the basis for structural as well as functional homology. The initial research on the role of the hippocampal formation in the homing behavior showed that this brain structure is likely to be involved in phenomena of spatial cognition. Therefore, the homing behavior of pigeons has been extensively used as an experimental model to investigate the role of the hippocampal formation in spatial cognition related to a naturally occurring behavior. These studies have revealed that the hippocampal formation plays a fundamental role in the learning of a navigational map based on atmospheric odors, but it doesn't seem to be involved in the operation of such a map. In contrast, both the learning and the operation of a navigational map based on the recognition of familiar landmarks require a functional hippocampal formation. Further investigations indicated that these functions of the hippocampal formation are mediated by its involvement in the use of the sun compass, and suggested that the hippocampal formation plays a fundamental role in a cognitive process in which the sun compass is specifically used to learn about the location of stimuli in space. The studies reviewed in the present paper have provided a considerable amount of experimental data both on the anatomical/neurochemical organization of the avian hippocampal formation and on the role played by this brain structure in spatial cognition. The future development of these researches will need to consider the contribution to hippocampal function of specific transmitter systems that are involved in hippocampal circuitry. In particular, the afferent cholinergic system and some of the peptidergic systems intrinsic to the hippocampal formation deserve particular attention in view of their possible involvement in the acquisition and/or operation of spatial cognitive abilities by homing pigeons.

Structure-activity relationships of 2-aryl-2,5-dihydropyridazino [4,3-b]indol-3(3H)-ones at the benzodiazepine receptor

A large series of 2-aryl-2,5-dihydropyridazino[4,3-b]indol-3(3H)ones (PIs) carrying properly selected substituents at the indole and N2-phenyl rings was prepared and tested as central benzodiazepine receptor (BZR) ligands and potential (anti)convulsant agents. Stereoelectronic requirements for high receptor affinity were detected by means of 2-D and 3-D QSAR analyses. BZR affinities and pharmacological profiles of the compounds were examined in comparison with some other pyridazinoindolones recently described by us and with pyrazoloquinoline (PQ) analogues. An anticonvulsant activity greater than PQs was generally observed for PIs. Notably, in the test of audiogenically induced seizures, one compound showed a potency comparable to that of diazepam.

Developmental expression of protein kinase C immunoreactivity in rod bipolar cells of the rabbit retina

Rod bipolar cells constitute the second-order neuron in the rod pathway. Previous investigations of the rabbit retina have evaluated the development of other components of the rod pathway, namely the dopaminergic and AII amacrine cell populations. To gain further insights into the maturation of this retinal circuitry, we studied the development of rod bipolar cells, identified with antibodies directed to the alpha isoform of protein kinase C (PKC), in the rabbit retina. Lightly immunostained PKC-immunoreactive (IR) somata are first observed at postnatal day (PND) 6 in the distal inner nuclear layer (INI.). Immunostaining is also observed in the outer plexiform layer (OPL), indicating the presence of PKC-IR dendrites. PKC-IR axons are present in the INL oriented toward the inner plexiform layer (IPL). Several of them terminate with enlarged structures resembling growth cones. At PND 8, some immunostained terminal bulbs, characteristic of rod bipolar cells, are detected in the proximal IPL. PKC-IR cells at PND 11 (cye opening) display stronger immunostaining and more mature characteristics than at earlier ages. The dendritic arborizations of these cells in the OPL and their axon terminals in the IPL attain mature morphology at later ages (PND 30 or older). The density of PKC-IR cells shows a peak at PND 11 followed by a drastic decrease up to adulthood. The total number of PKC-IR cells increases from PND 6 to PND 11 and then it remains almost unchanged until adulthood. The mosaic of PKC-IR cells is nonrandom in some retinal locations at PND 6, but the overall regularity index at PND 6 is lower than at older ages. The present data provide a comprehensive evaluation of the development of rod bipolar cells in the postnatal rabbit retina and are consistent with those previously reported for dopaminergic and AII amacrine cell populations, indicating that different components of the rod pathway follow a similar pattern of maturation, presumably allowing the rod pathway to be functional at eye opening.

Construction and analysis of a bacteriophage phi 6 gene 14 nonsense mutant

The production of a small low-abundance protein encoded by the large dsRNA genome segment of bacteriophage phi 6 in extracts of phage-infected Pseudomonas phaseolicola has been reported previously. Construction and analysis of a phage containing a nonsense mutation in this gene, designated gene 14, indicates that its product is not essential for growth in the laboratory. However, since early protein synthesis is delayed, burst sizes are reduced, and plaques are smaller than wild type, P14 is needed for optimal phage development.

Effects of high energy phosphates and L-arginine on the electrical parameters of ischemic-reperfused rat skeletal muscle fibers

In skeletal muscle, 4 h of ischemia followed by 30 min of reperfusion depolarizes the fibers, markedly increases the Cl- and glibenclamide-sensitive K+ conductances and reduces the excitability of the fibers. The ischemia-reperfusion also significantly decreases the ATP content of the muscles. In the present work, the electrical parameters of reperfused extensor digitorum longus muscle of rats were measured in vitro at 30 degrees C, by a computerized two-intracellular microelectrode technique, before and after in vivo pretreatment with equimolar doses of phosphocreatine disodium salt tetrahydrate, phosphocreatine di-L-arginine salt and L-arginine hydrochloride. In the same experimental situations the ATP content of the muscles was also measured. Both phosphocreatine salts prevented the increase of membrane ion conductance due to muscle reperfusion by preloading the muscle fibers with extra ATP. Phosphocreatine disodium salt also prevented the depolarization and restored the normal excitability of the reperfused fibers. In contrast, phosphocreatine di-L-arginine salt did not restore the resting potential nor the excitability of the fibers, but it decreased the amplitude of the action potential by reducing the overshoot. The pretreatment with L-arginine also failed to protect the electrical parameters of the fibers from the ischemic-reperfusion insult. Furthermore, the L-amino acid produced a more pronounced reduction of the excitability of the fibers by increasing the threshold current needed to elicit an action potential and reducing it overshoot. The in vitro application of L-arginine to the muscle also reduced the overshoot of the action potential, suggesting a direct interaction of the L-amino acid with Na+ channels.

AII amacrine cell population in the rabbit retina: identification by parvalbumin immunoreactivity

Parvalbumin (PV) is a calcium-binding protein localized to selected neurons in the nervous system, including the retina. This investigation evaluated the distribution of PV immunoreactivity in the rabbit retina using immunohistochemistry with a monoclonal antibody directed to carp PV. In the inner nuclear layer (INL), PV immunoreactivity was present in horizontal and amacrine cells. In the ganglion cell layer, PV immunostaining was confined to somata that are likely to be both displaced amacrine cells and ganglion cells. PV-immunoreactive (IR) amacrine cells were positioned in the proximal INL adjacent to the inner plexiform layer (IPL). These cells usually gave rise to a single primary process, which arborized into two distinct bands in the IPL. In sublamina a, the processes were thin and had large, irregular endings. In sublamina b, multiple processes branched from the primary process and were characterized by varicosities and spines. PV-IR amacrine cell bodies measured from 8 to 10 microns in diameter. Their density was highest in the visual streak and lowest in the periphery of the superior retina. The average number of PV-IR amacrine cells was 464,045 cells per retina (N = 3), and the average regularity index of the PV-IR cell mosaic was 3.23. PV-IR amacrine cells were further characterized by double-label immunofluorescence experiments using antibodies to PV and tyrosine hydroxylase (TH). Varicose TH-IR processes were in close apposition to many PV-IR amacrine cells and often formed "ring structures" around them. Together, these morphological, quantitative, and histochemical observations indicate that PV immunoreactivity in the INL is localized predominantly to AII amacrine cells, and therefore it is a valuable marker for the identification of this cell type.

In vitro packaging of individual genomic segments of bacteriophage phi 6 RNA: serial dependence relationships

Bacteriophage phi 6 has a genome of three segments of double-stranded RNA enclosed in a procapsid composed of four different proteins. The preformed procapsid is capable of packaging plus-strand transcripts of the genomic segments in an in vitro reaction. The packaging of the three segments shows a strong order of dependence in that segment S packages alone, but segment M requires S and and segment L requires S and M for efficient packaging. Packaging of individual segments is dependent on unique packaging sequences of about 200 nucleotides near the 5' ends of the segments. Deletions that invade these regions destroy packaging competence for the particular segment and for the dependent segments as well. In the presence of 2 mM phosphate and at magnesium ion concentrations above 4 mM, packaging becomes progressively more independent and ultimately nonspecific with respect to phi 6 sequences.

Posthatching development of preproenkephalin mRNA-expressing cell populations in the pigeon telencephalon

Enkephalin peptides are highly expressed in the vertebrate telencephalon. Our previous investigations in the pigeon and in the chicken [26] suggested that the cellular distribution of these peptides is conserved in phylogenetically 'old' telencephalic regions (e.g. the basal ganglia), while it has species-specific organizations in areas (e.g. dorsomedial forebrain and bulbus olfactorius) that are likely to play important roles in species-specific behaviors. In the present study, we investigated the posthatching development of preproenkephalin (PPE) mRNA-containing cells in the pigeon forebrain using in situ hybridization histochemistry. These cells are densely distributed in the paleostriatal complex (corresponding to the mammalian caudate-putamen) at hatching, and their density progressively decreases during the first 9 days posthatching, when it is similar to that of adult pigeons. In the dorsomedial forebrain (corresponding to the mammalian hippocampus), PPE mRNA-expressing cells are present at hatching, and their density reaches a peak around the 6th day posthatching. In the bulbus olfactorius, the first PPE mRNA-containing cells are observed after 9 days posthatching. The developmental profile of PPE mRNA expression in these areas of the pigeon telencephalon shows remarkable similarities with the development of enkephalinergic cells in corresponding brain areas of mammals. As in the mammalian caudate-putamen, the developmental expression of enkephalin peptides in the paleostriatal complex is likely to be related to neuronal withdrawal from the mitotic cycle. The developmental pattern of expression of PPE mRNA in the dorsomedial forebrain suggests that enkephalin peptides contribute to the maturation of the behavioral functions of this area.

X-ray crystal structure, partitioning behavior, and molecular modeling study of piracetam-type nootropics: insights into the pharmacophore

To detect possible molecular determinants of amnesia-reverting activity, the conformational properties of a number of rigid and flexible piracetam-type cognition enhancers have been assessed by X-ray diffraction, NMR spectroscopy, and ab initio and high-temperature-quenched molecular dynamics (QMD) calculations. The structures of the preferred conformers in solution derived from 1H-NMR spectral analysis were in good agreement with those found by QMD calculations. Interestingly, the calculation of the average molecular lipophilicity potential on the water-accessible surface of the selected conformers was helpful in interpreting the partitioning behavior observed by measuring octanol-water partition coefficients and capacity factors in reversed-phase high-performance liquid chromatography. While lipophilicity does not play a relevant role, the distance between polar groups, accounted for by the distance between carbonyl oxygens, emerges as a factor, among others, which should influence the amnesia-reversal activity of piracetam-type nootropics.

Preproenkephalin messenger RNA-containing amacrine cells in the chicken retina identified with in situ hybridization histochemistry

Enkephalin peptides are present in the retina of several vertebrate species. In the avian retina, enkephalin immunoreactivity is primarily localized to a population of amacrine cells. In the present study, we determined the localization of cells expressing preproenkephalin (PPE) mRNA, which encodes the precursor of enkephalin peptides, in adult as well as in embryonic chicken retinas. The localization of PPE mRNA-expressing cells to the proximal inner nuclear layer (INL) in the adult chicken retina is similar to that of enkephalin-immunoreactive cells observed in previous studies, indicating that amacrine cells expressing PPE mRNA synthesize Met5- and Leu5-enkephalin peptides and related extended forms. Specific hybridization signal is absent in retinas at embryonic day (E) 11, but it is detected in retinas at E 15 and at hatching. PPE mRNA-expressing cells at these ages are located in the proximal INL, and they can be classified as amacrine cells on the basis of their soma size and laminar position. These findings confirm and extend previous observations on the presence of opioid peptides in amacrine cells of the chicken retina. The presence of PPE mRNA at embryonic ages, together with the evidence that enkephalins influence developmental processes, suggests that these peptides modulate retinal maturation in birds.

Distribution of preproenkephalin mRNA in the chicken and pigeon telencephalon

Bioassay and immunological studies have detected the presence of opioid peptides in the nervous system of representatives of all classes of vertebrates. The present study evaluates the expression and localization of preproenkephalin (PPE) mRNA to determine the sites of synthesis of the enkephalin peptides in the adult chicken and pigeon telencephalon using in situ hybridization histochemistry. We used a 500-base-pair chicken RNA probe corresponding to chicken PPE cDNA. In both the chicken and the pigeon telencephalon, the highest concentration of PPE mRNA-containing cells was observed in the lobus parolfactorius, paleostriatum augmentatum, nucleus accumbens, and septum. Distinct populations of labeled cells were also detected in the hyperstriatum accessorium, hippocampus, area parahippocampalis, nucleus of the diagonal band, cortex dorsolateralis, and cortex piriformis. Differences in PPE mRNA expression between chicken and pigeon were observed in several telencephalic regions. For instance, the bulbus olfactorius was heavily labeled in the pigeon, but was not labeled in the chicken, and numerous PPE mRNA-containing cells were present in the area parahippocampalis of pigeons but not of chickens. In contrast, in the hyperstriatum dorsale and hyperstriatum ventrale, numerous PPE mRNA-expressing cells were detected in the chicken but not in the pigeon. Overall, PPE mRNA-expressing cells were more numerous than enkephalin-immunoreactive cells described in previous studies. In addition, our results suggest that the general pattern of enkephalin expression in the avian telencephalon is similar to that found in other vertebrates. Finally, the results of the present study illustrate some differences in the pattern of PPE mRNA distribution between closely related species, indicating the existence of species-specific neurochemical pathways, which may influence and perhaps mediate different behaviors characteristics of these species.

Reconstitution of active replicase in procapsids of the segmented dsRNA bacteriophage phi 6

Bacteriophage phi 6 has a genome of three segments of double-stranded RNA enclosed in a procapsid composed of four different proteins. The preformed procapsid is capable of packaging plus strand transcripts of the genomic segments in an in vitro reaction. The plus strands then serve as templates for in vitro minus strand synthesis. Procapsids that are missing protein P2 are incapable of minus strand synthesis. In this report we show that incubation with a cell extract containing P2 results in particles with normal amounts of attached P2 and with packaging and replicase activity. Particles lacking P7 have reduced replicase activity which can be augmented by incubation with extracts containing P7, but the amount of attached P7 is small.

Cyclic amidine analogues of taurine and homotaurine: synthesis and effects on rat skeletal muscle

A series of amidinosulfonic acids IIIa-f, analogs of taurine and homotaurine, was synthesized by reacting 2-aminoethane or 3-aminopropane sulfonic acid with lactim ethers Ia-c and then cyclized to sultams IVa-c and Vd-f. The effects of some selected amidinosulfonic acids III on membrane ionic conductances of rat skeletal muscle are described.

A new small low-abundant nonstructural protein encoded by the L segment of the dsRNA bacteriophage phi 6

A new small low-abundant protein encoded by the large genome segment of bacteriophage phi 6 has been detected in extracts of Escherichia coli bearing phi 6 cDNA clones and in extracts of phage-infected Pseudomonas phaseolicola. This 62 amino acid protein, designated P14, has a net charge of +2 at pH 7.0. Gene 14 has been located by deletion analysis and N-terminal protein sequence. Expression of P14 is down-regulated in E. coli when the complete L segment clone is expressed. Polyclonal antibodies to P14 detected the new protein in small amounts in phage-infected cells but not in phi 6 virions or nucleocapsids, or in procapsids assembled in E. coli. Procapsids assembled in E. coli after expression of phi 6 L segment clones with or without gene 14 had essentially similar protein composition and activity in an in vitro packaging and replication system. Thus P14 does not appear to be essential for the structure or assembly of functional procapsids. P14 might, however, facilitate packaging in vivo. Alternatively this protein could play in a role in repair of host membranes following viral penetration.

Effects of taurine analogues on chloride channel conductance of rat skeletal muscle fibers: a structure-activity relationship investigation

In rat skeletal muscle, taurine was proposed to interact with a low affinity binding site on sarcolemmal phospholipids near chloride channel, increasing chloride conductance (GCl). In an attempt to evaluate the structure-activity relationship between taurine and its binding site, a series of N-azacycloalkenyl analogues of taurine (A: N-(1'aza-cyclohepten-2'yl)-2-aminoethane sulfonic acid; B: N-(1'-aza-cyclopenten-2'-yl)-2-aminoethane sulfonic acid; C: N-(1'-aza-cyclohepten-2'-yl)-3-amino-propane sulfonic acid; D: N-(1'aza-cyclopenten-2'-yl)-3-aminopropane sulfonic acid) have been synthetized and tested in vitro on rat extensor digitorum longus (EDL) muscle. In spite of the presence of a bulky and lipophilic 5 or 7 membered heterocycle linked to the taurine amino group, analogues A and B determined an increase of GCl, although less potently than taurine. Also 3-amino-propane sulfonic acid (homotaurine), tested in comparison, showed less activity in increasing GCl with respect to taurine, probably for the increased distance between charged groups. Taurine analogues C and D, which differ from compounds A and B for an additional methylene group, showed much lower activity in increasing GCl. It has been reported that guanidinoethane sulfonate (GES) displaces taurine from the low affinity site on sarcolemma by only 7%. This compound, characterized by lower charge density on the guanidinium cationic head, applied in vitro on EDL muscle, show reduced taurine-like activity in increasing GCl.(ABSTRACT TRUNCATED AT 250 WORDS)

Vasoactive intestinal polypeptide/peptide histidine isoleucine messenger RNA in the rat retina: adult distribution and developmental expression

In the adult nervous system, vasoactive intestinal polypeptide acts as a neurotransmitter or neuromodulator, and during development, it may also act as a neurotrophic factor. In the adult mammalian retina, this peptide is contained in a population of wide-field amacrine cells. Using in situ hybridization histochemistry, we examined the distribution and developmental expression of vasoactive intestinal polypeptide/peptide histidine isoleucine messenger RNA in the rat retina. Retinas collected from birth to adulthood were hybridized with an RNA probe as whole mounts, and then cut either perpendicular or parallel to the vitreal surface. Adult retinas were used in double labeling experiments for the visualization of both the hybridization signal and vasoactive intestinal polypeptide immunoreactivity in the same tissue section. In adult retinas, vasoactive intestinal polypeptide/peptide histidine isoleucine messenger RNA is localized to amacrine cells positioned in the proximal inner nuclear layer, and rarely to displaced amacrine cells in the inner plexiform layer and ganglion cell layer. The neurons expressing this messenger RNA are sparsely distributed, with a non-random distribution and densities of about 190 cells/mm2. An estimate of their total number gives about 12,350 cells/retina. The double labeling experiments showed that the hybridization signal is specifically confined to neurons displaying vasoactive intestinal polypeptide immunoreactivity. Vasoactive intestinal polypeptide/peptide histidine isoleucine messenger RNA is first detected at postnatal day 5 in cells located in the proximal part of the neuroblastic layer. A greater number of these neurons is present in the inner nuclear layer at postnatal day 10, and a few labeled neurons are also detected in the inner plexiform layer and in the ganglion cell layer. At this time, vasoactive intestinal polypeptide/peptide histidine isoleucine messenger RNA-containing amacrines in the inner nuclear layer are non-randomly distributed on the retinal surface, as in adult retinas. At postnatal day 15 (eye opening), there is a peak in both the density and the estimated number of labeled neurons, and their pattern of distribution in the retinal layers is similar to that in the adult. The present study shows that in the adult rat retina vasoactive intestinal polypeptide and peptide histidine isoleucine are synthesized in a sparsely distributed amacrine cell population, extending previous immunohistochemical findings. The appearance of vasoactive intestinal polypeptide peptide histidine isoleucine messenger RNA during the first postnatal week is consistent with the reported appearance of other transmitter-identified amacrine cell populations.(ABSTRACT TRUNCATED AT 400 WORDS)

Connections of the piriform cortex in homing pigeons (Columba livia) studied with fast blue and WGA-HRP

The piriform cortex in homing pigeons receives a projection from the olfactory bulb and is necessary for the operation of those aspects of the navigational map based on olfactory stimuli in these animals. The afferent and efferent projections of the piriform cortex were studied using retrograde migration of wheat-germ agglutinin horseradish peroxidase (WGA-HRP) and Fast Blue, and anterograde migration of WGA-HRP. The piriform cortex was found to receive projections from, and send projections to, numerous regions and nuclei in the telencephalon, diencephalon and lower brainstem. A reciprocal connection with the parahippocampal region suggests that the piriform cortex and hippocampal formation may be part of a neural system that regulates navigational map learning. The piriform cortex also connects reciprocally with a large portion of the anterior telencephalon, including the cortex prepiriformis and hyperstriatum dorsale. In general, the pathway connections of the piriform cortex in homing pigeons are similar to those of the piriform cortex in mammals.

2-Aryl-2,5-dihydropyridazino[4,3-b]indol-3(3H)-ones: novel rigid planar benzodiazepine receptor ligands

A series of 2-aryl-2,5-dihydropyridazino[4,3-b]indol-3(3H)-ones 5 were prepared and evaluated for their ability to inhibit radioligand binding to BZR, and to prevent sound and pentylenetetrazole (PTZ) induced seizures in mice. The biological and pharmacological results are discussed in the light of some recently proposed pharmacophore models and compared through molecular orbital and molecular modeling studies to those obtained from the close pyrazoloquinoline analogs 6.