Days Of Saline Treatment Research Articles

Comparative study on growth traits and ions regulation of zoysiagrasses under varied salinity treatments.

Salt stress affects plant physiology, development, and growth. This research investigated varied salinity levels on growth traits and ions accumulation of four zoysiagrasses and aimed to identify phenotypic traits associated with variability in salinity tolerance. In this study, “S001” zoysiagrass (Zoysia sinica), “Diamond” zoysiagrass (Zoysia matrella), “J026” zoysiagrass (Zoysia japonica), and “M001” zoysiagrass (Zoysia macrostachya) were grown in plastic pots and exposed to 1/2 Hoagland nutrient solution amended with different amounts of NaCl for 120 days. At the end of the experiment, growth traits and ion contents were determined. The results showed that the salt-tolerance of four zoysiagrasses ranked as “M001” > “Diamond” > “J026” > “S001” according to percent green leaf canopy area (GLCA) after 120 days of salinity treatment. Although dry leaf weight, leaf length/width, and shoot height were significantly decreased by salinity treatments for all turfgrasses, the salt-tolerant species had a smaller drop. Besides, ions secretion capacity and Na+ concentration in leaf and root increased, but K+ concentration together with leaf and root K+/Na+ ratios decreased with the increasing concentration of the salinity. However, the salt-tolerant species exhibited strong K+ absorption and transportation ability and a high salt secretion capacity. The results indicated that growth traits and ions regulation were related to variability in tolerance of diverse zoysiagrasses to salt stress.

Alleviation of salt stress and expression of stress-responsive gene through the symbiosis of arbuscular mycorrhizal fungi with sour orange seedlings

The objective of this study was to investigate the effect of arbuscular mycorrhizal fungi (AMF from Glomus genus) inoculation on salt tolerance and the expression of CaSISP gene in sour orange (Citrus aurantium L.) seedlings. Forty-day-old sour orange seedlings were inoculated with G. mosseae + G. intraradices, G. mosseae + G. hoi, G. intraradices + G. hoi, G. mosseae + G. intraradices + G. hoi and kept for 175 days, then treated with 0 (control), 35 and 70 mM NaCl. After 45 days of salinity treatment, some physiological, biochemical and growth parameters as well as the expression pattern of Stress-Inducible Small Protein (SISP) gene were determined. Under salt stress, mycorrhizal inoculated plants had higher growth, higher chlorophyll content, better water status, higher gas exchange capacity (increased photosynthetic rate, stomatal conductance and transpiration rate), lower electrolyte leakage, malondialdehyde and hydrogen peroxide contents and higher osmolytes accumulation and antioxidant defense systems response compared to non-mycorrhizal treated plants (control). Moreover, abscisic acid levels were lower in colonized plants, indicating that they were less stressed than the controls. On the other hand, we demonstrated for the first time that the expression of CaSISP gene was influenced by both AMF symbiosis and salinity stress. Our study showed that the plants inoculated with the triple combination of fungi based on some of morphological, physiological and biochemical characters were more tolerant to salt stress than the others suggesting the application of AMF colonization as a practical way to improve citrus production under salt stress condition.

Morphological and Genetic Diversity within Salt Tolerance Detection in Eighteen Wheat Genotypes.

Salinity is a major obstacle to wheat production worldwide. Salt-affected soils could be used by improving salt-tolerant genotypes depending upon the genetic variation and salt stress response of adapted and donor wheat germplasm. We used a comprehensive set of morpho-physiological and biochemical parameters and simple sequence repeat (SSR) marker technique with multivariate analysis to accurately demonstrate the phenotypic and genetic variation of 18 wheat genotypes under salinity stress. All genotypes were evaluated without NaCl as a control and with 150 mM NaCl, until the onset of symptoms of death in the sensitive plant (after 43 days of salinity treatment). The results showed that the relative change of the genetic variation was high for all parameters, heritability (>60%), and genetic gain (>20%). Stepwise regression analysis, noting the importance of the root dry matter, relative turgidity, and their respective contributions to the shoot dry matter, indicated their relevance in improving and evaluating the salt-tolerant genotypes of breeding programs. The relative change of the genotypes in terms of the relative turgidity and shoot dry matter during salt stress was verified using clustering methods. For cluster analysis, the genotypes were classified into three groups: tolerant, intermediate, and sensitive, representing five, six, and seven genotypes, respectively. The morphological and genetic distances were significantly correlated based on the Mantel test. Of the 23 SSR markers that showed polymorphism, 17 were associated with almost all examined parameters. Therefore, based on the observed molecular marker-phenotypic trait association, the markers were highly useful in detecting tolerant and sensitive genotypes. Thus, it considers a helpful tool for salt tolerance through marker-assisted selection.

Indole-3-Acetic Acid Rescues Plant Growth and Yield of Salinity Stressed Tomato (Lycopersicon esculentum L.)

Soil is a medium for plant growth and provides support, minerals and water to the plant for survival. Soil salinity declines availability of water to the plant, affect microorganisms growth, and water drainage capacity of soil, which adversely affect plant growth and development. In the present work the effect of indole-3-acetic acid (IAA) on growth and yield of salinity stressed tomato (Lycopersicon esculentum L.) was studied. Salinity levels (0 [control, no NaCl], 30 and 60 mM of NaCl) were applied to the soil and IAA concentrations (0 [control, no IAA], 100 and 200 ppm) were sprayed on the plants after ten days of salinity treatment. The statistical analysis showed that salt stress conditions adversely affected plant height, branches per plant, stem diameter, fruits per plant, fruit diameter, fruit length, total chlorophyll content, root length, root fresh weight, roots dry weight, and yield per plant, while IAA application to salinity stressed tomato plants rescued the plants and had significantly positive effects on growth and yield of tomato plants. In the light of above results, it is concluded that foliar application of IAA may rescue the salinity stressed tomato plants.

Autotetraploidization in Ziziphus jujuba Mill. var. spinosa enhances salt tolerance conferred by active, diverse stress responses

Chinese jujube (Ziziphus jujuba Mill.), native to China, is an important deciduous fruit tree. This species is mainly propagated by grafting, with Z. jujuba var. spinosa widely used as the rootstock because of its resistance to adverse conditions such as saline environments. In a previous study, we found that autotetraploid jujube is phenotypically superior to the corresponding diploid, furthermore, the differences in salt tolerance between the two plant materials and the underlying molecular mechanism were still unclear. To clarify this issue, we investigated the leaf and shoot morphology and physiology of diploid and autotetraploid plants treated with NaCl for 0, 2, 6, 10, and 14 days. We also carried out transcriptome profiling after 0, 1, and 2 days of salinity treatment. Comparisons of diploid and autotetraploid plants under salinity conditions in morphology and eight physiological traits indicating that the autotetraploid has superior salt tolerance. Many differentially expressed genes related to salt stress response in diploid and autotetraploid Z. jujuba were assigned to functional categories such as detoxification, stimulus response, catalytic enzyme activity, antioxidant enzyme activity, glutathione metabolism, phenylpropanoid biosynthesis, flavonoid biosynthesis, peroxisome, plant hormone signaling, and ABC transport. These genes constituted a complex regulatory network for maintaining osmosis and intracellular ion homeostasis and resisting oxidative stress. In addition, several genes encoding MYB, AP2/ERF-ERF, WRKY, GRAS, and C2H2 as well as hub proteins, including aquaporins, heat stress transcription factors, chaperone, cytochrome P450, and kinases, were differentially expressed under salt stress. The number, function, and fold changes of these genes differentially expressed under salinity treatment differed between the diploid and its autotetraploid, with more active, diverse strategies taking place in the autotetraploid to adapt to long-term salt stress. Finally, we found that there were more up-regulated DEGs and greater fold change related to osmotic adjustment in autotetraploid than in diploid which could further explain the enhanced salt stress tolerance in the autotetraploid. Our findings contribute to an understanding of the genetic basis of salt tolerance in autotetraploid jujube, which can guide future tolerance breeding of jujube cultivars and their rootstocks.

Comparative study of transcriptional and physiological responses to salinity stress in two contrasting Populus alba L. genotypes

Soil salinity is an important limiting factor to tree growth and productivity. Populus alba L. is a moderately salt-tolerant species and its natural populations are adapted to contrasting environments, thus providing genetic resources to identify key genes for tolerance to abiotic stress, such as salinity. To elucidate the molecular and genetic basis of variation for salinity tolerance in P. alba, we analyzed the short-term ecophysiological and transcriptome response to salinity. Two contrasting genotypes, 6K3, salt sensitive, and 14P11, salt tolerant, originating from North and South Italy, respectively, were challenged with salt stress (200 mM NaCl). Sodium accumulated in the leaves of salt-treated plants and its concentration increased with time. The net photosynthesis was strongly reduced by salinity in both genotypes, with 6K3 being significantly more affected than 14P11. The transcriptional changes in leaves were analyzed using cDNA microarrays containing about 7000 stress-related poplar expressed sequence tags (EST). A microarray experiment based on RNA pooling showed a number of salinity--regulated transcripts that markedly increased from 3 h to 3 days of salinity treatment. Thus, a detailed analysis was performed on replicated plants collected at 3 days, when ~20% of transcripts showed significant change induced by salinity. In 6K3, there were more genes with decreased expression than genes with increased expression, whereas such a difference was not found in 14P11. Most transcripts with decreased expression were shared between the two genotypes, whereas transcripts with increased expression were mostly regulated in a genotype-specific manner. The commonly decreased transcripts (71 genes) were functionally related to carbohydrate metabolism, energy metabolism and photosynthesis. These biological processes were consistent with the strong inhibition of photosynthesis, caused by salinity. The commonly increased transcripts (13 genes) were functionally related to primary metabolism and biosynthesis of proteins and macromolecules. The salinity-increased transcripts discriminated the molecular response of the two genotypes. In 14P11, the 21 genes specifically salinity-induced were related to stress response, cell development, cell death and catabolism. In 6K3, the 15 genes with salinity-increased expression were involved in protein biosynthesis, metabolism of macromolecules and cell organization and biogenesis. The difference in transcriptome response between the two genotypes could address the molecular basis of intra-specific variation of salinity tolerance in P. alba.

Hormonal responses of nodulated Medicago ciliaris lines differing in salt tolerance

Hormonal changes in two Medicago ciliaris lines differing in salt tolerance (TNC 1.8 being more tolerant than TNC 11.9) were studied as possible regulators of growth and symbiotic nitrogen fixation (SNF). After 21 days of saline treatment (100mM NaCl), four major phytohormones (abscisic acid, ABA; the cytokinin trans-zeatin, t-Z; the auxin indole-3-acetic acid, IAA; and the ethylene precursor 1-aminocyclopropane-1-carboxylic acid, ACC) were analysed. Salinity differently affected hormone concentrations in vegetative tissues and nodules in both lines. Principal component analysis (PCA) revealed that growth and SNF parameters under salinity were inversely correlated to the amount of reduced nitrogen (Nred) allocated to the roots and nodules, to the sucrolytic activity (TSA) in the roots, and to the t-Z and ABA concentration in the nodules. However, those parameters were positively associated along PC1 to the Nred and TSA in the leaves and all the hormones analysed in the roots. Interestingly, the ACC concentration of all organs was positively associated with vegetative growth and with SNF under salinity, as a putative regulator of the symbiotic-parasitic relation with the bacteria. The influence of hormonal changes in relation to plant growth, SNF and symbiotic relation is discussed.

Salt-Induced Stress Effects on Biomass, Photosynthetic Rate, and Reactive Oxygen Species-Scavenging Enzyme Accumulation in Common Bean

ABSTRACT We studied the effects of salinity stress on biomass production, photosynthesis, water relations, and activity of antioxidant enzymes in two cultivars of common bean (‘HRS 516’ and ‘RO21’). Seedlings were raised in nutrient solution supplemented with increasing concentrations of sodium chloride (NaCl) at 0, 50, and 100 mM. After 10 days of salinity treatment, the plants were sampled to determine the enzyme activity, protein content and dry biomass. Plant biomass and activities of most antioxidant enzymes were adversely affected by salinity stress. Leaf osmotic potential was found to be directly proportional to salt stress. The cultivar, ‘HRS 516’ accumulated less sodium (Na+) than ‘RO21’. Under salinity, superoxide dismutase (SOD) enzyme activity increased 3 folds in both bean cultivars (‘HRS 516’ and ‘RO21’) compared to other antioxidants (APX, CAT, and GR). While not neglecting other possible factors, photosynthesis and biomass remains reliable indicators of plant functioning in response to salinity stress.

Detection of the Moderately Beneficial Cognitive Effects of Low-Dose Treatment with Haloperidol or Clozapine in an Animal Model of the Attentional Impairments of Schizophrenia

The absence of effective cognition enhancers for the treatment of patients with schizophrenia limits the validation of animal models and behavioral tests used for drug finding and characterization. However, low doses of haloperidol and clozapine were documented to produce moderately beneficial effects in patients. Therefore, this experiment was designed to determine the attentional effects of such treatments in a repeated-amphetamine (AMPH) animal model. Animals were trained in an operant-sustained attention task and underwent a 40-day pretreatment period with saline or increasing doses (1-10 mg per kg) of AMPH. After regaining baseline performance following 10 days of saline treatment, animals were treated with haloperidol (0.025 mg per kg), clozapine (2.5 mg per kg), or vehicle for 10 days. Furthermore, the effects of AMPH challenges (1.0 mg per kg) were assessed. In AMPH-pretreated animals, the administration of AMPH challenges resulted in the disruption of attentional performance. Treatment with haloperidol and clozapine attenuated the detrimental performance effects of these challenges, with clozapine exhibiting more robust attenuation. Furthermore, clozapine, but not haloperidol, impaired the performance of control animals. In contrast, the performance of AMPH-pretreated animals remained unaffected by clozapine. As this animal model detects the moderately beneficial cognitive effects of haloperidol and clozapine, it may be useful for preclinical research designed to detect and characterize treatments for the cognitive symptoms of schizophrenia.

Effect of ACTH (tetracosactide) on steroid hormone levels in the mare: Part A: Effect in intact normal mares and mares with possible estrous related behavioral abnormalities

Ovariectomized mares and mares with inactive ovaries may show signs of estrus. The reason behind this phenomenon is not clear; however, steroid hormones of adrenal origin have been suggested. Moreover, aberrant adrenal hormone production has been implied as a reason why some intact mares may change behavior. In the present study, the effect of ACTH on plasma levels of cortisol, progesterone, androstenedione and testosterone was investigated in intact mares with normal estrous behavior (‘controls’, n = 5) and intact mares that according to their owners showed deviant estrous behavior (‘problem’ mares, n = 7). Blood samples were collected hourly from 12:00 h until 14:00 h the following day (half-hourly between 14:00 and 17:00 h) on two occasions (at two estruses), with saline or ACTH treatment (tetracosactide) at 14:00 h (saline treatment day or ACTH treatment day). ACTH treatment caused a significant increase in plasma levels of cortisol, progesterone, androstenedione and testosterone in all mares ( P < 0.05). An overall significant difference in cortisol response to ACTH was found ( P < 0.05), with ‘problem’ mares showing a significantly lower increase in cortisol levels 30 min to 3 h post ACTH treatment ( P < 0.001). The ‘problem’ mares also showed a significantly higher increase than controls in progesterone levels in the same time period ( P < 0.05). The reason for the reduced adreno-cortical reactivity, with a low cortisol response to the ACTH treatment, in the ‘problem’ mares is unknown, but may indicate a difference in adrenal function as compared to control mares.

Effect of ACTH (tetracosactide) on steroid hormone levels in the mare: Part B: Effect in ovariectomized mares (including estrous behavior)

The mare is the only non-primate species known to display estrous signs after ovariectomy and adrenal hormones have been implicated as a possible cause. Moreover, in several species, estradiol seems to have a stimulatory effect on the hypothalamic–pituitary–adrenal axis. The aim of the present study was to compare the effect of ACTH (tetracosactide) on pertinent hormones [cortisol, progesterone, androstenedione, testosterone (intact and ovariectomized mares) and estradiol (ovariectomized mares only)] in intact mares in estrus with the same mares after ovariectomy ( n = 5). Blood samples were collected hourly from 12:00 until 14:00 h the following day (half-hourly between 14:00 and 17:00 h) on two occasions, with saline or ACTH treatment at 14:00 h (saline treatment day or ACTH treatment day). The mares, both when intact and after ovariectomy, showed a significant increase in all measured hormones, except estradiol (not measured in intact mares), after ACTH treatment, lasting at least 3 h post-treatment ( P < 0.001). On the saline treatment day, cortisol levels in ovariectomized mares were lower than in intact mares in the evening (18:00–23:00 h), but higher at night (24:00–05:00 h). No differences in cortisol response between mares, when intact and after ovariectomy, were found after ACTH treatment ( P = 0.3). Androstenedione levels were lower ( P < 0.001) and increased less after ACTH treatment in ovariectomized mares, as compared to when intact ( P < 0.05). Progesterone concentrations were lower in the ovariectomized mares at night (24:00–05:00 h) on the saline treatment day and at all times on the ACTH treatment day ( P < 0.05). Testosterone concentrations were lower in ovariectomized mares on both treatment days, as compared to when intact ( P < 0.001). It was concluded that ovariectomy affected basal cortisol pattern. Ovarian androstenedione and testosterone contributed to the basal circulating levels and, in the case of androstenedione, was stimulated by ACTH. Endogenous estradiol did not act stimulatory on adrenal gland hormone production in the mare.

Optimizing microarray in experimental hypertension

Genetic noise between outbred animals can potentially be a major confounder in the use of microarray technology for gene expression profiling. The study of paired organs from the same animal offers an alternative approach (e.g., for studies of the kidney in experimental hypertension). The present study was undertaken to determine the level of genetic noise between outbred adult Sprague-Dawley (SD) rats, and to determine the effects of unilateral nephrectomy on changes in gene expression as a basis for the design of microarray studies in experimental hypertension. Male SD rats (approximately 130 g) were acclimatized before measurement of tail-cuff systolic blood pressure (SBP) for 6 control days and 4 days of saline treatment. Left kidney nephrectomy was performed, and the tissue snap-frozen in liquid nitrogen for subsequent RNA extraction. Two weeks later, SBP was measured over 4 control and 8 saline treatment days, and the remaining right kidney removed and frozen. Total RNA purification, preparation of cRNA, hybridization, and scanning of the Rat U34A Affymetrix arrays were performed, and data analyzed using MAS5 software Affymetrix Suite (v5), Bioconductor, as well as statistical methods motivated by relevant simulations. Gene expression profiles in the left control kidney were extremely consistent across animals. The expression profiles of pairs of kidneys from the same animal were, however, more similar than those of kidneys from different animals. Nephrectomy had little effect on the gene expression profiles in the time frame examined. Despite the outbred nature of the rats used in this study, they are useful for gene expression profiling comparisons. The use of paired organs from an individual animal ensures even further genetic identity, allowing determination of genes modified by the treatment of interest.

Hemodynamic Effects of the Nitric Oxide Donor DETA/NO in Mice

(Z)‐1‐[N‐(2‐aminoethyl)‐N‐(2‐ammonioethyl)amino]diazen‐1‐ium‐1,2‐diolate (DETA/NO) is a recently synthesized member of NO‐releasing, polyamine zwitterions, the so‐called NONOates, that spontaneously liberate NO in aqueous solutions. The aim of this study was to determine the hemodynamic effects of DETA/NO in normotensive and hypertensive mice. Male Swiss Outbred mice were implanted with TA11PA‐C20 blood pressure devices (Data Sciences International, USA). After recovery (7–10 days), blood pressure was monitored for 10 days while mice were receiving saline (0.1 ml/20 g/day, s.c.). Mice were then treated every four hours for 1 day with either DETA/NO 60 mg/kg i.p. or the inactive metabolite, diethylenetriamine 38 mg/kg (molar equivalent) i.p. After a 2 week wash‐out period, mice were treated with adrenocorticotrophic hormone (ACTH: 500 µg/kg/day, s.c.) for 10 days and re‐challenged with DETA/NO or diethylenetriamine. Results were expressed as mean ± SEM. After 10 days of saline treatment, baseline systolic and diastolic blood pressure (BP) were similar for animals subsequently receiving DETA/NO or the amine (123 ± 1/95 ± 3 and 124 ± 1/92 ± 0.2 mmHg) respectively. DETA/NO induced a profound fall in BP [Systolic: 74 ± 4 mmHg (− 40 ± 3%); Diastolic: 46 ± 4 mmHg (− 52 ± 4%)] and an increase in heart rate [729 ± 33 bpm (32 ± 2%)] within the first 80 minutes. Diethylenetriamine had no effect. ACTH treatment increased BP in both groups (137 ± 16/108 ± 12 and 161 ± 1/142 ± 1 mmHg) respectively. DETA/NO induced a profound fall in blood pressure [Systolic: 92 ± 11 mmHg (− 32 ± 7%); Diastolic: 68 ± 10 mmHg (− 35 ± 10%)] and an increase in heart rate [613 ± 36 bpm (18 ± 6%)] within the first 80 minutes. Again diethylenetriamine had no significant effect. There was no significant effect on body weight with any treatment. Thus DETA/NO has potent blood pressure lowering effects in both normotensive and hypertensive mice.

Tetracosactid (ACTH) treatment of mares in estrus—effect on estrous signs, ovulation and hormone levels

Ovariectomized mares and mares with inactive ovaries may show signs of estrus. The reason behind this phenomenon is not clear; however, steroid hormones of adrenal origin have been suggested. Moreover, aberrant adrenal hormone production has been implied as a reason why some intact mares may change behavior. In the present study, the effect of ACTH on plasma levels of cortisol, progesterone, androstenedione and testosterone was investigated in intact mares with normal estrous behavior (‘controls’, n = 5) and intact mares that according to their owners showed deviant estrous behavior (‘problem’ mares, n = 7). Blood samples were collected hourly from 12:00 h until 14:00 h the following day (half-hourly between 14:00 and 17:00 h) on two occasions (at two estruses), with saline or ACTH treatment (tetracosactide) at 14:00 h (saline treatment day or ACTH treatment day). ACTH treatment caused a significant increase in plasma levels of cortisol, progesterone, androstenedione and testosterone in all mares (P < 0.05). An overall significant difference in cortisol response to ACTH was found (P < 0.05), with ‘problem’ mares showing a significantly lower increase in cortisol levels 30 min to 3 h post ACTH treatment (P < 0.001). The ‘problem’ mares also showed a significantly higher increase than controls in progesterone levels in the same time period (P < 0.05). The reason for the reduced adreno-cortical reactivity, with a low cortisol response to the ACTH treatment, in the ‘problem’ mares is unknown, but may indicate a difference in adrenal function as compared to control mares.

Cerebral dopamine and noradrenaline in mice withdrawn from repeated morphine treatment and development of tolerance to a test dose of morphine

1. In mice withdrawn from 3 days of morphine, dopamine depletion was significantly ( P < 0.01) retarded in the “rest of the forebrain and midbrain” and tended to be retarded in the striatum. 2. In control mice withdrawn from 3 days of saline treatment a 10 mg/kg test dose of morphine significantly enhanced noradrenaline depletion in all selected brain areas. This did not occur in test mice withdrawn from 1–3 days of morphine, indicating development of tolerance. 3. These results suggest that dopamine depletion is retarded in the “rest of the forebrain and midbrain” of mice withdrawn from 3 days of repeated morphine and that noradrenaline depletion is unchanged in all selected brain areas of mice withdrawn from morphine. 4. Tolerance develops to the enhancing effect of morphine on noradrenaline depletion in mice withdrawn from 3 days of repeated morphine but not in those withdrawn from 1 day of treatment only.

Growth, water relations and solute composition of Phaseolus vulgaris L. under saline conditions

In this work, the influence of increasing external NaCl on relative growth rate, water relations and the degree of osmotic adjustment achieved by Phaseolus vulgaris plants have been studied. Both shoots and roots of plants grown in saline media were smaller after 13 days of saline treatment. Concentrations of NaCl of 25 mM and lower, although decreasing plant weight, did not appreciably affect relative growth rate of plants. The concentrations of both Cl − and Na + in leaves significantly increased as the concentration of NaCl was increased in the nutrient solution. The concentration of K + was also significantly increased with salinity, whereas leaf Ca 2+ content remained unaffected. Plants exposed to NaCl concentrations of up to 50 mM did not differ from control plants in total sugars and proline concentrations. However, the presence of 100 mM NaCl in the external solution significantly increased total sugars and proline. The general tendency of organic acid concentrations was to decrease with salinity. The relative contribution of inorganic ions to the decrease in osmotic potential was 0.45 MPa, about 88%, whereas organic compounds contributed with 0.04 MPa, about 8%. The results are discussed in order to explain the inhibition of growth observed upon saline treatment as well as which solutes are implicated in the process of osmoregulation.

Cholinergic blockade and response timing in rats.

The effects of central cholinergic blockade on the temporal regulation of behaviour were studied with a two-level DRL schedule. Five-month-old male Wistar rats had to press lever A and then wait for a minimum of 5 s before pressing lever B to obtain the reinforcer (sweetened milk). After a stable baseline performance, subjects were injected in random order with the general cholinergic blocker, scopolamine, 0.15 and 0.5 mg/kg, the peripheral cholinergic blocker, methylscopolamine, 0.15 and 0.5 mg/kg, and a combination of the cholinesterase inhibitor, physostigmine, 0.2 mg/kg, and scopolamine, 0.5 mg/kg. Each drug treatment was separated by 2 days of saline treatment. Results showed that scopolamine at 0.5 mg/kg significantly impaired the temporal regulation of the A-B response sequence: the median A-B inter-response time (IRT) was shortened and the coefficient of variation of the A-B IRT distribution was increased, thus revealing a loss in the sensitivity to time. This disruption of accurate timing behaviour lowered efficiency. The drug changed neither the duration of the B-A interval nor the A-B response rate, but significantly increased the rate of the superfluous B-B sequences. Methylscopolamine was without effects and physostigmine totally or partially reversed all the scopolamine effects. These results suggest that scopolamine at 0.5 mg/kg specifically affected the mechanism(s) underlying response timing, and that the effects were not secondary to changes in activity or motivation. They partly corroborate data obtained in other procedures and support the idea that the central cholinergic system is involved in the temporal regulation of behaviour.

The Effect of Anteroventral Third Ventricular Lesions on the Changes in Cholecystokinin Receptor Density in the Rat Supraoptic Nucleus Following Saline Drinking

Abstract Autoradiography and computerized image analysis were used to study the density of Cholecystokinin binding sites in the supraoptic nucleus of sham-lesioned and anteroventral third ventricle (AV3V)-lesioned animals in which the magnocellular system had been activated by salt-loading with 2% saline for 48 h. Rats were maintained in metabolic cages for 5 to 7 days prior to a sham- or AV3V-lesioning procedure, and the ratio of sodium intake:urinary sodium output used as a measure of sodium excretion. Following the sham or lesion procedure half of the rats had their drinking water replaced with 2% saline and the other half were maintained on normal drinking water. Neurohypophysial hormone levels were measured by specific radioimmunoassay in trunk blood samples taken 48 h after the saline or water treatment. The AV3V-lesioned group of animals were characterized by an inability to excrete the excess sodium load and by a failure to increase secretion of both oxytocin and vasopressin into the general circulation in response to the salt-stimulus. Despite this inappropriate response, [(125) l]cholecystokinin octapeptide binding in the oxytocin-rich dorsal portion of the supraoptic nucleus was similarly elevated in both sham- and AV3V-lesioned rats following 2 days of saline treatment. These results suggest that the magnocellular oxytocin system is capable of responding to an osmotic stimulus even when the release of hormone has been severely impaired.

A quantitative study of the ultrastructural changes in the hypothalamo-neurohypophysial system during and after experimentally induced hypersecretion.

Substitution of a 2% solution of sodium chloride in place of drinking water for 3 days significantly increased both the size of neurosecretory neurones in the supraoptic and paraventricular nuclei of rats and the proportion of these cells which had dilated endoplasmic reticulum. There was an increase in the number of multivesicular bodies per mean cell profile and also an increase in the ratio of “dense” (immature) to “pale” (mature) neurosecretory granules within the perikarya, although the total numbers of granules were unchanged. If, after 3 days of saline-treatment, the rats were again allowed tap water to drink for 2 days, the proportion of cells showing dilated endoplasmic reticulum and the number of multivesicular bodies returned towards normal, but there was a significant increase in the number of large dense lysosomal bodies per cell profile and a relative increase in the proportion of “pale” (mature) neurosecretory granules. These changes suggest that the increased bio-synthetic activity resulting from saline-treatment subsides when the treatment is terminated. Furthermore, since neurohypophysial hormone stores have still not returned to normal in animals of the recovery group, they also imply the absence of an internal feedback system by which the level of neural lobe hormone stores might govern the synthetic activity of the neurosecretory cells. Both the increased synthesis, and the increased electrical activity which accompanies it, may be independent consequences of the depleting stimulus.