Atriopeptin prevents angiotensin II-stimulated glucose utilization in the subfornical organ

Effects of peptides on animal and human behavior: a review of studies published in the first twenty years of the journal Peptides

This review catalogs effects of peptides on various aspects of animal and human behavior as published in the journal Peptides in its first twenty years. Topics covered include: activity levels, addiction behavior, ingestive behaviors, learning and memory-based behaviors, nociceptive behaviors, social and sexual behavior, and stereotyped and other behaviors. There are separate tables for these behaviors and a short introduction for each section.

Intraperitoneal atrial natriuretic peptide increases peritoneal fluid and solute removal

BACKGROUND

Atrial natriuretic peptide (ANP) is a hormone with well-known diuretic and vasodilating properties. Recently it was reported that ANP could increase the peritoneal fluid formation and increase peritoneal solute clearance. This study investigated the effect of ANP on peritoneal fluid and solute transport characteristics.

METHODS

Eighteen male Sprague-Dawley rats were divided into three groups. A four-hour dwell study using 25 mL 2.27% glucose dialysis solution with 50 microg/kg ANP (N = 6, H-ANP) or 5 microg/kg ANP (N = 6, L-ANP) or without ANP (N = 8, control) and frequent dialysate and blood sampling was done in each rat. Radiolabeled human albumin (RISA) was added to the solution as an intraperitoneal volume marker.

RESULTS

The intraperitoneal volume was significantly higher in the H-ANP group as compared with the control group and the L-ANP group. The drainage volume was 26.2 +/- 1.1, 25.5 +/- 0.7, and 29.8 +/- 0.8 mL for the control, L-ANP, and H-ANP groups, respectively (P < 0.01). This was related to significant differences in the peritoneal fluid absorption rates (K(E); estimated as the RISA elimination coefficient): 39 +/- 3, 38 +/- 3, and 19 +/- 4 microL/min, and in the direct lymphatic absorption rate (K(EB); estimated as the clearance of RISA from dialysate to blood): 7 +/- 1, 6 +/- 1, and 4 +/- 1 microL/min for the control, L-ANP, and H-ANP groups, respectively (all P < 0.01). No differences were found in the intraperitoneal volume, K(E), and K(EB) between the control group and the L-ANP group. The diffusive mass transport coefficient (K(BD)) for urea, sodium, potassium, and total protein did not differ among the three groups. However, the glucose D/D(0) was significantly higher, and the K(BD) for glucose was significantly lower in the H-ANP group as compared with the other two groups. Solute clearances (+175% for sodium and +26% for potassium) were significantly increased in the H-ANP group, mainly as a result of the increased fluid removal in this group.

CONCLUSIONS

Our results suggest that ANP may decrease peritoneal fluid absorption (by 51%, partially because of decreasing the direct lymphatic absorption), resulting in a significant increase in peritoneal fluid removal and small solute clearances. While the basic diffusive permeability of the peritoneal membrane was not changed, the peritoneal glucose absorption was retarded by adding ANP to peritoneal dialysate, perhaps through interaction of ANP with glucose metabolism.

Nitric oxide synthase in the subfornical organ of Mongolian gerbil (Meriones unguiculatus), mouse and rat

The present paper aims to contribute to the knowledge of the histophysiologic role of the subfornical organ. Using nicotinamide adenine dinucleotide phosphate diaphorase histochemistry (NADPH-diaporase) and nitric oxide synthase immunocytochemistry, we detected a high concentration of the neuronal isoform of nitric oxide synthase in neurons of the subfornical organ of the adult Mongolian gerbil (Meriones unguiculatus), mouse and rat. Our results suggest that neurons of the subfornical organ produce a considerable amount of nitric oxide which acts, not only as a neurotransmitter, but could also diffuse into cerebral blood vessels and cerebrospinal fluid.

CNS effects of peptides: a cross-listing of peptides and their central actions published in the journal Peptides, 1986-1993

The centrally mediated effects of peptides as published in the journal Peptides from 1986 to 1993 are tabulated in two ways. In one table, the peptides are listed alphabetically. In another table, the effects are arranged alphabetically. Most of the effects observed after administration of peptides are grouped, wherever possible, into categories such as cardiovascular and gastrointestinal. The species used in most cases has been rats; where other animals were used, the species is noted. The route of administration of peptides and source of information also are included in the tables, with a complete listing provided at the end. Many peptides have been shown to exert a large number of centrally mediated effects.

Regulatory role of brain angiotensins in the control of physiological and behavioral responses

Considerable evidence now indicates that a separate and distinct renin-angiotensin system (RAS) is present within the brain. The necessary precursors and enzymes required for the formation and degradation of the biologically active forms of angiotensins have been identified in brain tissues as have angiotensin binding sites. Although this brain RAS appears to be regulated independently from the peripheral RAS, circulating angiotensins do exert a portion of their actions via stimulation of brain angiotensin receptors located in circumventricular organs. These circumventricular organs are located in the proximity of brain ventricles, are richly vascularized and possess a reduced blood-brain barrier thus permitting accessibility by peptides. In this way the brain RAS interacts with other neurotransmitter and neuromodulator systems and contributes to the regulation of blood pressure, body fluid homeostasis, cyclicity of reproductive hormones and sexual behavior, and perhaps plays a role in other functions such as memory acquisition and recall, sensory acuity including pain perception and exploratory behavior. An overactive brain RAS has been identified as one of the factors contributing to the pathogenesis and maintenance of hypertension in the spontaneously hypertensive rat (SHR) model of human essential hypertension. Oral treatment with angiotensin-converting enzyme inhibitors, which interfere with the formation of angiotensin II, prevents the development of hypertension in young SHR by acting, at least in part, upon the brain RAS. Delivery of converting enzyme inhibitors or specific angiotensin receptor antagonists into the brain significantly reduces blood pressure in adult SHR. Thus, if the SHR is an appropriate model of human essential hypertension (there is controversy concerning its usefulness), the potential contribution of the brain RAS to this dysfunction must be considered during the development of future antihypertensive compounds.

Early development of the human area postrema and subfornical organ

The first appearance and early development of two circumventricular organs, the area postrema (AP) and the subfornical organ (SFO), were investigated in human embryos and fetuses from the 4th to the 40th gestational weeks (GW). The AP appears very early in development, during the GW 10; its high vascularization can be seen from GW14, and differentiated neurons are observed from GW 16. The SFO is characterized by a late onset of development. It can first be distinguished at GW 17, but it does not attain cytological differentiation until the last weeks of gestation. It is suggested that the AP has important functions during fetal life, which are related to normal fetal weight and growth; in contrast the SFO, which is connected with drinking behavior and salt/water balance, seems to play a less essential role in early fetal life.