Immunoreactive (ir) beta-endorphin (b-END) and dynorphin (DYN) in rat brain and pituitary were measured after food and water deprivation and from brains taken during either day or night. In other rats, eating and drinking were measured following lesions in the arcuate n. Ir-DYN levels are higher in hypothalamus and lower in pituitary at night. Deprivation, particularly water deprivation, increases hypothalamic, day-time ir-DYN. Water deprivation decreases pituitary levels of ir-DYN. Arcuate-lesions, depleting both ir-b-END and ir-DYN, do not modify total daily intake of water or food but does modify circadian rhythmicity of eating and drinking. These data support the conclusion that b-END and DYN are involved in maintaining day-night patterns of eating and drinking.

Animals↗

PubMedDate not supplied

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.

Analgesia↗

PubMedDate not supplied

The effect of enkephalin dimers on body temperature in mice.

Short-lasting decrease in rectal temperature in mice after intraperitoneal administration of an enkephalin dimer, the so called double-enkephalin--(Tyr-D-Ala-Gly-Phe-NH)2 (D-ENK-O)--at dose 0.1, 0.5, 1, 2.5, 5, 10 and 20 mg/kg of body weight was observed. Another double-enkephalin--Tyr-D-Ala-Gly-Phe-NH-(CH2)3-HN-Phe-Gly-D-Ala-Tyr-- fai led to produce this effect. The hypothermic effect of D-ENK-O was almost completely reduced by naloxone which suggests an involvement of opiate receptors in the D-ENK-O produced hypothermia in mice.

Animals↗