Differential effects of DGAVP on acquisition and extinction of active avoidance behavior.

DGAVP facilitates consolidation and retrieval of active and passive avoidance behavior. In this study it was tested whether the long-term behavioral effects of DGAVP are the consequence of an initial increase in behavioral arousal during the learning phase. Animals that were preestimated in an open field test to be low active showed a lower number of conditioned avoidance responses (CAR's) during acquisition and extinction of a shuttle-box task than high active rats.

The effect of AVP and DGAVP on the exploratory activity of rats.

The effects of [8-L-arginine] vasopressin (AVP) and desglycinamide [8-L-arginine] vasopressin (DGAVP) were tested on the exploratory activity of adult male rats in a novel environment. The inherited individual differences in the non-specific excitability level of the animals were ascertained prior to the drug administration and the rats were then distributed evenly into the experimental groups. One half of each groups contained the less excitable and the other the more excitable animals.

On the blood-brain barrier to peptides: accumulation of labelled vasopressin, DesGlyNH2-vasopressin and oxytocin by brain regions.

After intracarotid injection of 125I-arginine vasopressin (AVP), 125I- or 3H-lysine vasopressin (LVP), 3H-DesGlyNH2-arginine vasopressin (DGAVP), and 125I- or 3H-oxytocin (OXT), the accumulation of radioactivity was determined in 13 to 18 brain regions and anterior pituitary in rats. Calculated extraction by tight capillary regions amounts to about 1-2% independently of the peptide doses injected (4 X 10(-4) to 5 X 10(-9) mol-1). This indicates a low but measurable extraction of labelled peptides which furthermore is nonsaturable.

Natriuretic properties of [2-p-ethylphenylalanine] deamino-6-carba-oxytocin (Nacartocin) in cats.

Nacartocin, a synthetic analogue of oxytocin, [2-L-p-phenylalanine]deamino-6-carba-oxytocin has a specific natriuretic effect in cats. The doses of 0.05-10 micrograms/kg b.

Nacartocin--analogue of oxytocin with enhanced natriuretic properties: natriuretic and hemodynamic characteristics.

Nacartocin, [2-p-ethylphenylalanine]deamino-6-carba-oxytocin, is almost three times more potent than oxytocin as a natriuretic agent. The natriuretic effect is mainly due to the inhibitory action of the peptide on tubular sodium resorption. Nacartocin decreased the blood pressure of anesthetized rats by the decrease of the total peripheral resistance which was greater than that observed after oxytocin administration.

Specificity of the effect of desglycinamide (8-D-arginine) deaminovasopressin on short--term memory.

The effect of desglycinamide (8-D-arginine) deaminovasopressin (desgly NH2 dDAVP) on learning was studied in rats using the conditioned taste aversion (CTA) paradigm. Desgly NH2 dDAVP (3 micrograms/kg) applied 40 min before presentation of the gustatory CS (0.1 % saccharin) did not affect CTA formation, when the visceral US (0.

Vasopressin analogues and spatial working memory in the 24-arm radial maze.

The effect of vasopressin analogues dAVP, dDAVP, and desgly NH2 dDAVP on working memory was tested in the 24-arm radial maze in twelve 6-month-old and twelve 19-month-old rats. No age dependent effects were found. All three peptides tested (3 micrograms/kg) tended to improve the performance but only the desgly NH2 dDAVP significantly decreased the number of errors.

Comparison of antidiuretic and natriuretic effects of [8-lysine]vasopressin and [8-D-arginine]deaminovasopressin in conscious rats.

The relation between the duration of antidiuresis and sodium excretion and the route of administration of [8-lysine-vasopressin or [8-D-arginine]-deaminovasopressin to conscious rats was investigated. Both compounds were administered either intravenously through a chronically inserted catheter in the right jugular vein, or subcutaneously. The rats were then placed into individual metabolic cages and urine was collected quantitatively.

Vasopressin analogues and spatial short-term memory in rats.

The effect of vasopressin analogues on short-term memory was tested in the 12-arm radical maze. After the first 6 choices rat (n = 16) were removed from the apparatus and allowed to complete the remaining 6 choices 20 min later. Whereas desgly-NH2-VP, AVP, dAVP and dDAVP (3.

Effect of some oxytocin analogues on natriuresis in rats.

Non-anaesthetized rats were used for studying the relationship between the amount of sodium excreted and structural modifications of oxytocin molecule. Any change performed in position 4 (i.e.

DI patient refractory to vasopressin and dDAVP: absence of antibodies to AVP and dDAVP and inactivating factor in blood serum.

Antibodies to either AVP or dDAVP were sought in the serum of a patient suffering from diabetes insipidus and treated with Adiuretin (Spofa) to which the patient had become refractory. Neither the antibodies nor the presence of enzymes inactivating LVP was detected in the serum.

Oral urine recycling in diabetes insipidus (DI) rats--the role of the gut in absorption of some urinary components.

Brattleboro rats with diabetes insipidus (DI) will, if no other fluid is offered, drink their own previous day's urine. Such oral urine-recycling, where normal elimination is effective only in 15%, does not result in clinical or laboratory signs of uraemia even after 20 days. Serum electrolytes and creatinine remained normal, serum osmolarity and urea were slightly raised, but none of the parameters measured could be classified as uraemic.

Role of the disulfide bridge and the C-terminal tripeptide in the antidiuretic action of vasopressin in man and the rat.

The antidiuretic action of a number of vasopressin analogues has been measured in the rat and man in water diuresis. These analogues had the following categories of structural alteration: a) substitution of -CH2CH2-(dicarba) and -SCH2-(6-monocarba) for the natural -SS- bridge between residues 1 and 6, b) changes in the nature of the C-terminal tripeptide produced by substitution of D-arginine and L-Nalpha-methylarginine for L-arginine in sequence position 8 and L-leucine for proline in position 7, and c) combinations of a and b. In addition, a highly active analogue which results when valine is substituted for glutamine in position 4 was tested.