Dynorphin-(1-13) is a potent in vivo suppressor of vasopressin levels in the rat.

Intracerebroventricular administration of dynorphin-(1-13) inhibits dose-dependently plasma vasopressin level in normal as well as in water-deprived rats, whereas systemic (subcutaneous) administration of this opioid peptide is ineffective in this respect. Simultaneous subcutaneous, but not intracerebroventricular, administration of naloxone prevents the suppressive effect of dynorphin-(1-13) on plasma vasopressin levels.

Characterization of the alpha-MSH-like immunoreactivity in blood and cerebrospinal fluid of the rat.

We have investigated the nature of the alpha-melanocyte stimulating hormone-like immunoreactivity (alpha-MSH-LI) in blood and cerebrospinal fluid (CSF) of the rat. Blood and CSF from intact animals were subjected to high pressure liquid chromatography (HPLC) followed by a radioimmunoassay (RIA) specific for the C-terminal part of the alpha-MSH molecule. It appeared that in both body fluids the predominant alpha-MSH-LI co-migrated with synthetic alpha-MSH and not with its des-acetyl or di-acetyl analogues.

The effect of gamma-type endorphins on alpha-MSH release in the rat.

Neuroleptic drugs increase the level of alpha-melanotropin (alpha-MSH) in the blood of the rat. We have investigated whether neuroleptic-like peptides, the gamma-type endorphins, also affect alpha-MSH release. A structure-activity study revealed that (des-enkephalin)-gamma-endorphin (DE gamma E, beta-LPH-(66-77), beta-endorphin-(6-17)) is able to increase plasma alpha-MSH levels after intracerebroventricular injection, while the longer gamma-type endorphins, i.

Changes in cerebrospinal fluid levels of vasopressin and oxytocin of the rat during various light-dark regimes.

Levels of arginine-vasopressin (AVP) and oxytocin (OXT) in cerebrospinal fluid (CSF) of rats were determined at various times of the day and the night under normal and changed light-dark conditions. During a regular daily 14 h light and 10 h dark cycle (lights on 06.00 h, off 20.