preproenkephalin and beta-neo-endorphin

Experiments were conducted (i) to determine the hemodynamic (blood pressure and heart rate) responses of conscious rats following intrathecal (IT) administration of endogenous prodynorphin-derived opioids into the lower thoracic space, (ii) to identify the receptors involved in mediating their cardiovascular responses, and (iii) to reveal any possible hemodynamic interactions with the neuropeptide arginine vasopressin. Male Sprague-Dawley rats were surgically prepared with femoral arterial and venous catheters as well as a spinal catheter (into lower thoracic region, T9-T12). After recovery, hemodynamic responses were observed in conscious rats for 5-10 min after IT injections of artificial cerebrospinal fluid (CSF) solution, prodynorphin-derived opioids (dynorphin A, dynorphin B, dynorphin A (1-13), dynorphin A (1-10), alpha- and beta-neoendorphin, leucine enkephalin (LE), methionine enkephalin (ME), arginine vasopressin (AVP), or norepinephrine (NE)). IT injections of AVP (10 or 20 pmol), dynorphin A (1-13), or dynorphin A (10-20 nmol) caused pressor effects associated with a prolonged and significant bradycardia. Equimolar (20 nmol) concentrations of LE, ME, alpha- and beta-neoendorphin, and dynorphin A (1-10) caused no significant blood pressure or heart rate changes. Combined IT injections of dynorphin A (1-13) and AVP caused apparent additive pressor effects when compared with the same dose of either peptide given alone. IT infusion of the specific AVP-V1 antagonist d(CH2)5Tyr(Me)AVP before subsequent IT AVP, dynorphin A (1-13), or NE administration inhibited only the subsequent pressor responses to AVP. The kappa-opioid antagonist (Mr2266) infused IT blocked the pressor actions of subsequent dynorphin A administration and not AVP or NE.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Arginine Vasopressin; beta-Endorphin; Blood Pressure; Dynorphins; Endorphins; Enkephalin, Leucine; Enkephalin, Methionine; Enkephalins; Heart Rate; Hemodynamics; Injections, Spinal; Male; Narcotics; Norepinephrine; Peptide Fragments; Protein Precursors; Rats; Rats, Inbred Strains

The effect of leumorphin (LM), one of big leu-enkephalins derived from preproenkephalin B, on PRL secretion was studied in the rat in vivo and in vitro. Intracerebroventricular injection of synthetic porcine LM (0.06-6 nmol/rat) caused a dose-related increase in plasma PRL levels in urethane-anesthetized male rats and in conscious freely moving rats. Intravenous injection of LM (3 nmol/100 g BW) also raised plasma PRL levels in these animals. The plasma PRL response to intracerebroventricular LM (0.6 nmol/rat) was blunted by naloxone (125 micrograms/100 g BW, iv). The stimulating effect of LM on PRL release was the most potent among the peptides derived from preproenkephalin B. In in vitro studies, PRL release from superfused anterior pituitary cells was stimulated in a dose-related manner by LM (10(-9)-10(-6) M), and the effect was blunted by naloxone (10(-5) M). These results suggest that LM has a potent stimulating effect on PRL secretion from the pituitary in the rat by acting, at least in part, directly at the pituitary through an opiate receptor.

Topics: Animals; beta-Endorphin; Dynorphins; Endorphins; Enkephalins; Injections, Intraventricular; Male; Naloxone; Pituitary Gland, Anterior; Prolactin; Protein Precursors; Rats; Swine; Thyrotropin-Releasing Hormone

Dehydration significantly reduced the concentration of immunoreactive dynorphin A(1-17), dynorphin A(1-8), alpha-neo-endorphin, beta-neo-endorphin, and leu-enkephalin in the rat pituitary posterior-intermediate lobe. A statistically significant increase in immunoreactive dynorphin A(1-8), alpha-neo-endorphin and leu-enkephalin was observed in the hypothalamus. Comparison of the molar ratios of dynorphin A(1-17): dynorphin A(1-8) and alpha-neo-endorphin: beta-neo-endorphin showed an altered profile of stored pro-dynorphin cleavage products in the posterior-intermediate lobe of the pituitary of dehydrated rats.

Topics: Animals; beta-Endorphin; Dehydration; Dynorphins; Endorphins; Enkephalin, Leucine; Enkephalins; Food Deprivation; Hypothalamus; Male; Peptide Fragments; Pituitary Gland, Posterior; Protein Precursors; Rats; Rats, Inbred Strains

The distribution of peptides derived from the novel opioid peptide precursor proenkephalin B (prodynorphin) was studied in lobes of the pituitary with antibodies against alpha-neoendorphin (alpha-neo-E) beta-neoE, dynorphin (DYN)-(1-17), DYN-(1-8), and DYN B in combination with gel filtration and high pressure liquid chromatography. In the posterior pituitary, all five opioid peptides occurred in high and about equimolar concentrations, whereas putative precursor peptides were found in only minor quantities. In contrast, in the anterior pituitary immunoreactive (ir-) DYN-(1-17) and ir-DYN B consisted exclusively of a common precursor species with a mol wt of about 6000. Six thousand-dalton DYN may be comprised of the C-terminal portion of proenkephalin B, with the sequence of DYN-(1-17) at its N-terminus. Moreover, the major portions of ir-alpha-neo-E and ir-beta-neoE in the anterior pituitary were found to be of an apparent mol wt of 8000. These findings indicate a differential processing of the opioid peptide precursor proenkephalin B in the two lobes of the pituitary. The anterior pituitary seems to process proenkephalin B predominantly into high mol wt forms of neo-E and DYNs, whereas in the posterior pituitary proenkephalin B undergoes further proteolytic processing to the smaller opioid peptides alpha-neo-E, beta-neo-E, DYN-(1-17), DYN-(1-8), and DYN B. Thus, processing differences may enable the selective liberation of different (opioid) peptides with distinct biological properties from one precursor within different tissues.

Topics: Animals; beta-Endorphin; Chromatography, High Pressure Liquid; Dynorphins; Endorphins; Enkephalin, Leucine; Enkephalins; Male; Molecular Weight; Peptide Fragments; Pituitary Gland; Pituitary Gland, Anterior; Pituitary Gland, Posterior; Protein Precursors; Radioimmunoassay; Rats; Rats, Inbred Strains; Tissue Distribution