Anna Maria Konecka

Double-enkephalins—Synthesis, activity on guinea-pig ileum, and analgesic effect ☆

We have synthesized enkephalin analogues in which C-terminal methionine or leucine residues are replaced by a second active fragment of the enkephalin analogue. Synthesis of two compounds is described: in one, two fragments of a D-Ala2-enkephalin analogue are connected by a -NH-NH-bridge, and in the other, three methylene groups are incorporated between the amino groups. The first compound is a very potent inhibitor of electrically induced contractions of guinea-pig ileum and produces a strong analgesia when administered intraperitoneally in mice. The second compound is less active on the ileum and fails to produce analgesia after systemic injection. The double-enkephalins may interact with mu-receptors.

Circadian rhythm of pain in male mice

1. Circadian rhythm of pain in response to the thermal stimuli was assessed in male mice. 2. The hot-plate method was used. Response latencies were measured every 2 hours and showed a sinusoidal rhythm. 3. Minimal latencies were observed at 10 and 20 h, the highest were obtained at 12 and 4 hours. 4. The circadian changes in pain sensitivity may play an important role in many experiments on stress and post-stress analgesia as well as on susceptibility to pharmacological agents.

The effect of food and water deprivation on post-stress analgesia in mice and levels of beta-endorphin and dynorphin in blood plasma and hypothalamus

Pain sensitivity of food and/or water-deprived male mice was tested on a hotplate. The most pronounced analgesia ensued in animals given no food and water, and no food but water ad libitum, the least one in water-deprived mice. The magnitude of the rise in pain threshold depended on the duration of deprivation and was correlated with the increase in the blood plasma beta-endorphin level. In the hypothalamus beta-endorphin level increased after 72-h food deprivation only. The level of dynorphin remained unchanged. Naloxone (10 mg/kg) almost completely reversed food or water-deprivation induced analgesia.

Stressors and pain sensitivity in CFW mice. Role of opioid peptides

Effects of several environmental situations on pain threshold were studied in CFW male mice. Immobilization induced significant and naloxone reversible analgesia. Isolation produced analgesia which was partially reversed by naloxone. One minute swimming in + 4 degrees C or + 42 degrees C water increased naloxone reversible analgesia. Isolation produced analgesia which was partially reversed by naloxone. One minute swimming in 4 degrees C or + 42 degrees C water increased naloxone irreversible pain threshold. Other situations: drinking 2% NaCl solution, disturbance of light-dark cycle or social aggregation did not produce analgesia. The role of these situations as stress-inducers, as well as the role of endogenous opioid peptides in stress-induced analgesia, were discussed.

The effect of intracerebroventricular infusion of morphine, methionine-enkephalin and D-Ala2-Met-enkephalinamide on body temperature of rabbits

The effect of intracerebroventricular infusions of two synthetically obtained peptides: Met-enkephalin hydrochloride and D-Ala2-Met-enkephalinamide hydrochloride, and of morphine hydrochloride on rectal temperature was investigated in conscious rabbits. Morphine hydrochloride in a dose of 240 micrograms and D-Ala2-Met-enkephalinamide hydrochloride in doses of 240 and 3000 micrograms produced a hyperthermia which was accompanied by ear vasoconstriction and shivering. No such effect ensued after Met-enkephalin, possibly due to rapid enzymatic degradation of this compound. The concept of opioid involvement in the central thermoregulatory mechanism is discussed.

Effect of Cholesterol-Enriched Diet on Liver and Heart Enzymes in Male Rabbits

White New Zealand male rabbits were fed a high-cholesterol (1%) diet for 7 weeks. The activity of alkaline phosphatase (AP), alanine (AlaAT), aspartate (AspAT) aminotransferases and level of glucose in the blood plasma of rabbits was determined and compared with those of a control group of animals. The cholesterol-enriched diet resulted in increases in plasma AlaAT and AP activity and a decrease in plasma glucose. In the liver, cholesterol treatment decreased the activity of AspAT, AlaAT, AP, phosphoglucomutase, phosphofructokinase, pyruvate kinase and lactate dehydrogenase. Activities of glucosephosphate isomerase, aldolase and the level of glycogen were not affected. No statistically significant changes in the activity of examined enzymes in heart of rabbits fed with cholesterol-enriched diet were observed. Chronic intake of cholesterol in the diet had a negative effect on liver metabolism but not on heart metabolism in rabbits.

Responses Upon Multiple Administration of L-Thyroxine in Hens*

SummaryStudies on the influence of repeated injections of L-thyroxine on enzyme activity and total protein level in the blood plasma of White Rock and Sussex hens have shown that:1.The total protein level in both races decreased significantly.2.Activity of aldolase increased in White Rock hens while in Sussex hens it increased considerably only after the last injection.3.Activity of alanine aminotransferase did not change in White Rock hens and increased in the blood plasma of Sussex hens.4.In both races, the activity of aspartate aminotransferase increased initially and changed after L-thyroxine injection.5.Activity of alkaline phosphatase increased in White Rock hens, while in Sussex hens it decreased.6.Statistically significant differences between activities of examined enzymes in both races after L-thyroxine administration were found.

Suppression of Food and Water Intake after Intracerebroventricular Infusion of Morphine and Naloxone in Rabbits

The effect of intracerebroventricular infusion of morphine and naloxone on food and water intake was investigated in rabbits. Morphine hydrochloride at a dose of 120, 10 and 5 micrograms produced statistically significant suppression of 24-h food and water intake. The same effect ensued after infusion of naloxone at dose of 120 and 10 micrograms. Postmorphine aphagia was accompanied by a rise in blood free fatty acids and normal glucose levels. No changes were seen after naloxone.

Contracting activity of C-terminal fragments and a C-terminal hexapeptide analogue of substance P on non-stimulated and electrically stimulated isolated guinea-pig ileum

Abstract 1. C-terminal fragments of substance P containing up to 5 amino acids and a C-terminal hexapeptide analogue were synthesized, and compared with respect to their ability to contract isolated guinea-pig ileum and to raise the level of electrically elicited contractions. 2. The C-terminal tripeptide was the least effective compound. 3. The potency of the peptides increased in parallel on non-stimulated and electrically stimulated ileum with elongating the chain from 3 to 6 amino acids.

Effect of naloxone-reversible immobilization stress on the adrenal acetylcholinesterase activity in mice.

In male mice immobilized during 30 min, statistically significant increase in adrenal acetylcholinesterase (Ache) activity--up to 154% of control value--has been observed. Naloxone pretreatment (10 mg/kg b.w., ip.) suppressed that increase, Ache activity remaining at the level of non-immobilized, saline treated mice. This suggests the role of opioid peptides in this change. Ganglionic blockade by hexamethonium markedly inhibited Ache activity in adrenals of non-immobilized and of immobilized mice. Opioid peptides secreted from the splanchnic nerve terminals seem to be involved in the control of cholinergic mechanisms.