Neuropeptides as neuronal growth regulating factors. Peripheral nerve regeneration and the development of sexually dimorphic and motor behavior

Neuropeptides: general characteristics and neuropharmaceutical potential in treating CNS disorders

The general characteristics of neuropeptides are discussed as a background for the understanding of their role in regulation of physiological systems. The extent of those systems that are crucially affected by neuropeptides is vast and the complexity of their interactions makes the clinical focus on a specific neuropeptide unsatisfactory. The clinical potential of neuropeptides affecting eating disorders, CNS behavioral disorders and the neuroregenerative and neuroprotective action of neuropeptides is discussed. It is probable that successful neuropeptide therapeutics will depend upon the application of translational and combinational research using various ingenious combinations of neuropeptides, their agonists and antagonists, neuropeptide receptor agonists and antagonists, improved methods of delivery and the development of peptides targeted to the genetic profile of individual patients.

Maternal stress, HPA activity, and fetal/infant outcome

Preliminary conclusions from our research include the possibility that each of the HPA products evaluated, even though correlated (e.g., ACTH and beta E), may be linked to unique and specific outcomes. Maternal stress during the 28-30 weeks of gestation is associated with birth outcome. Increased levels of psychosocial stress were significantly related to gestational age at birth and infant birth weight. Maternal stress during the third trimester was associated with increased maternal plasma levels of ACTH and cortisol. This finding is consistent with possible mechanisms whereby psychosocial stress influences birth outcome. CRH controls the timing of labor and delivery. Precocious elevation of CRH is related to the risk of preterm delivery. This system may be "stress-sensitive." Even though pregnant women may be immunized from stress, the stress signal that is transmitted (release of ACTH and cortisol) is amplified by the placental release of CRH. This possibility has at least two consequences: (1) influencing the timing of delivery and (2) desensitization of hypophyseal corticotrophs and further "protection" of the pregnant women from the results of stress (i.e., release of ACTH and beta E). Beta E appears to influence fetal learning and perhaps the developing nervous system.

Cloning, expression, and tissue distribution of a fifth melanocortin receptor subtype

The melanocortin (MC) peptides mediate a diverse spectrum of biological activities in both the central nervous system and peripheral tissues by interacting with specific guanine nucleotide binding (G protein)-coupled receptors. Previously, four human melanocortin receptor subtypes have been cloned and characterized. In this study, we have isolated mouse complementary DNA (cDNA) and human genomic clones encoding a fifth melanocortin receptor subtype, MC5. Melanocortin peptide stimulation of human MC5, transiently expressed in COS1 cells, results in activation of adenylate cyclase with the following rank order of potency: [Nle4, D-Phe7]-alpha-MSH (melanocyte stimulating hormone) > ACTH (1-24) (adrenocorticotropic hormone) > alpha-MSH > beta-MSH > gamma-MSH. Northern blot hybridization, ribonuclease protection, and reverse transcription/polymerase chain reaction assays indicate that mouse MC5 mRNA is most abundant in skeletal muscle and brain. Lower but detectable levels of MC5 mRNA are also found in RT2-2 retinal neuronal cells, lung, testis, spleen, heart, kidney, and liver.

Melanocortins as factors in somatic neuromuscular growth and regrowth

Melanocortins, non-corticotropic fragments of adrenocorticotropic hormone, accelerate growth of the developing neuromuscular system and regrowth of damaged neurons, both in the adult and neonatal rat. Morphological, electrophysiological and behavioral characteristics are all improved by melanocortins, which, however, vary in potency, with alpha-MSH being the most effective. Tissue substrate, dosage, critical time periods and pattern of neuropeptide administration are all important variables. Melanocortins protect central neurons affecting motor behavior during development or following neuronal damage in the adult brain. Possible mechanisms of melanocortin action are discussed.

Neuroactive peptides: unique phases in research on mammalian brain over three decades

Because of the enormous growth over the last three decades of research on the role of peptides in the brain, the need became apparent to determine the status of these compounds in terms of their current research interest. Since 1965, over a quarter of a million research papers have been published on peptides that have since been classified as neuroactive. The present study was undertaken to analyze systematically the yearly trends of research emphasis in neuroactive peptides as reflected by their individual frequency of publication by year, beginning in 1966. A computer analysis of the publication characteristics was carried out using the Medline data base in which the citation search was limited to the topic brain crossed with the topic mammal. One criterion for the inclusion of a given peptide in the analysis was a frequency of 25 or more citations following its discovery, as related to the mammalian brain. The 42 peptides that met this criterion were: adrenocorticotropic hormone, angiotensin II, atrial natriuretic factor, bombesin, bradykinin, calcitonin, calcitonin gene-related peptide, carnosine, beta-casomorphin, cholecystokinin, corticotropin-releasing factor, delta sleep-inducing peptide, dynorphin, beta-endorphin, Leu-enkephalin, Met-enkephalin, galanin, gastrin, glucagon, growth hormone, growth hormone-releasing factor, insulin, kyotorphin, beta-lipotropin, luteinizing hormone-releasing factor, melanocyte-stimulating hormone release inhibitory factor-1, alpha-melanocyte-stimulating hormone, motilin, neurokinin A, neurokinin B, neuropeptide Y, neurotensin, oxytocin, pituitary adenylate cyclase activating polypeptide, peptide HI, prolactin, secretin, somatostatin, substance P, thyroid-releasing hormone, vasopressin, and vasoactive intestinal peptide. An overall analysis of the 298,105 papers published on these 42 peptides since 1965 revealed that the research activity of 24,742, or 8.30%, of the studies, focused on their neuroactive properties. Taken as a whole, the research on neuroactive peptides reached a peak in 1986, as reflected by the total of 1793 papers published during that year. Although the level of publication has fluctuated between 1548 and 1774 research papers over the last 6 years, it is now clear that the trend in research on neuroactive peptides has reached an asymptote today that shows no sign of deviation. A temporal analysis year by year of individual publication profiles revealed three distinct trends: 1) peptides showed a slow development in research interest and did not exceed more than 15-30 publications per year; 2) peptides exhibited a steady increase in research activity over the years that continues today; and 3) peptides displayed an initial, often intense, research emphasis that inexplicably declined, in some cases precipitously, in the mid 1980s.(ABSTRACT TRUNCATED AT 400 WORDS)

Melanotropins as growth factors

Peptides that regulate the growth of tissues, whether in a positive or negative manner, are termed growth factors. The melanocortins, neurotrophic sequences that correspond to peptide fragments contained within ACTH-(1-13), beneficially affect neural growth during development and regeneration. Analogues of ACTH-(4-9) (Org 2766) and ACTH-(4-10) (BIM 22015) are capable of sustaining neurite outgrowth from cultured dorsal root ganglion and spinal cord cells in the absence of nerve growth factor. The development of sexually dimorphic behavior in both male and female rats is influenced by perinatal administration of ACTH. This change appears to be correlated with changes in the growth and metabolism of developing serotonergic and dopaminergic systems in the hypothalamic nuclei associated with male and female sexual behavior. Similar melanotropic influences are found in the developing neuromuscular system. Neuromuscular development is accelerated by perinatal administration of melanocortins, provoking both nerve and muscle to attain early maturation. However, the responding tissue varies pivotally with age: early in gestation, embryonic muscle is acutely sensitive to peptide exposure; but once innervation has occurred, only the developing nerve reacts to melanocortin treatment. Melanocortins have little if any effect on the normal, adult neuromuscular system. Following peripheral nerve injury or pathology, melanotropins once again become effective growth factors, accelerating and enhancing nerve regeneration and muscle reinnervation. Electrophysiological, morphological, biochemical, and functional tests all indicate that ACTH-(4-10), Org 2766, BIM 22015, and alpha-MSH improve various facets of nerve regeneration, the degree to which the specific parameter is improved being dependent on the peptide fragment, its dosage, and pattern of administration. BIM 22015, while less effective as a neurotrophic factor, has potent myotrophic effects that the other peptides lack. Org 2766 may provide some protective action to the injured CNS as demonstrated by tests of cognitive function following brain lesions, although evaluation of recovery is sometimes enigmatic. Recovery from destruction of the nigrostriatal system is more easily measured through tests of motor function and open field behavior, both of which support a protective role for Org 2766. Compensatory mechanisms, including the presence of increased tyrosine hydroxylase and greater density of dopaminergic fibers, may be involved. Melanocortins are effective growth factors in sciatic nerve regeneration in neonatal rats. Both alpha-MSH and ACTH-(4-10) favor the formation of morphologically normal end plates despite the trauma following nerve crush at postnatal day 2.(ABSTRACT TRUNCATED AT 400 WORDS)

Cardiovascular haemodynamics of oriental hornet venom sac extract

The effects of hornet venom sac extract on the functioning of the cardiovascular system was assessed in dogs by concomitant examination of the following parameters: Systemic blood pressure, blood pressure and the dp/dt derivative of the left ventricle of the heart, heart rate, direct measurement of the left ventricular wall thickness, cardiac output, and body temperature. The effect of adult hornet venom sac extract on the canine cardiovascular system was rapid and led to a sharp drop in the systemic blood pressure, a similar drop in the pressure and dp/dt derivative in the left ventricle, to bradycardia, immediate thickening of the left ventricular wall and to an immediate rise in the cardiac output. As for the canine temperature, this dropped immediately following the administration of venom sac extract and remained at the new low level for at least 30 min. The smaller molecular weight components (less than 10 kilodalton) in venom sac extract have been found to be responsible for the immediate effects of venom sac extract on the cardiovascular system. On the other hand the high-molecular weight components exert more delayed effects which lead to a cumulative disturbance of cardiac function.

Mastoparan induces hypothermia in mice

The polypeptide mastoparan, isolated from the venom of the Oriental Hornet, Vespa orientalis, induces hypothermia in white mice 15 minutes after its intraperitoneal injection. The hypothermic effect is induced by mastoparan obtained from different hornet and wasp venoms. The normal murine core temperature is lowered by mastoparan from 38 degrees C to as far as 33 degrees C. This lowering lasts for one hour and is reversible.