Angiotensin II antagonists versus drinking induced by bombesin or eledoisin in pigeons

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.

Atypical angiotensin receptors may mediate water intake induced by central injections of angiotensin II and of serotonin in pigeons

Intracerebroventricular (i.c.v.) injection of serotonin (5-HT) in pigeons dose-dependently evokes a prompt and intense drinking behavior, which resembles that evoked by i.c.v. injections of angiotensin II (ANGII) in the same species. In the present study, we have examined the possible participation of central ANGII receptors in both ANGII- and 5-HT-evoked drinking behavior. The effects of i.c.v. injections of 5-HT (155 nmol), avian ANGII ([Asp(1),Val(5)]-ANGII, 0.1 nmol) or vehicle were studied in pigeons pretreated 20 min before with i.c.v. injections of the nonspecific ANGII receptor antagonist [Sar(1),Ile(8)]-ANGII (SAR; 1, 0.1 or 0.01 nmol), the AT(1) receptor antagonist losartan (2 or 4 nmol), the AT(2) receptor antagonist PD 123,319 (2 or 4 nmol) or vehicle (NaCl 0.15 M, 1 microl, n = 8/group). Immediately after treatment, they were given free access to water and drinking behavior was recorded during the next 60 min. At the doses presently used both 5-HT and ANGII treatments evoked comparable water intake amounts with similar behavioral profiles. While pretreatment with SAR dose-dependently reduced the water intake evoked by both 5-HT and ANGII, neither losartan nor PD 123,319 pretreatment affected the drinking induced by these treatments. The present results indicate that ANGII- and 5-HT-induced drinking in pigeons may be mediated by AT receptors possibly different from mammalian AT(1) and AT(2) receptors and suggest that activation of ANGII central circuits is a necessary step for the intense drinking induced by i.c.v. injections of 5-HT in this species.

Effects of angiotensin II and its blockers Sar1-Ile8-angiotensin II and DuP 753 on drinking in ducks in relation to properties of subfornical organ neurons

Properties of systemically applied angiotensin II in stimulating water intake of normally hydrated ducks were studied and the results compared with properties of angiotensin II-responsive neurons of the subfornical organ which are considered as targets for circulating angiotensin II acting as a dipsogen. Following intravenous infusion of hypertonic saline (2000 mosmol.kg-1 at 0.3 ml.min-1 for 1 h), intravenous infusion of 0.3 ml.min-1 isotonic saline with angiotensin II (200 ng.min-1), starting 1 h later, stimulated drinking in each case at an angiotensin II plasma level of about 1400 pg.ml-1. Without hypertonic priming, the same angiotensin II infusion did not stimulate drinking in each experiment; however, if effective, repeated infusions of ANGII induced stable dipsogenic responses. Angiotensin II infusions did not alter plasma levels of antidiuretic hormone. Sar1-Ile8-angiotensin II, a non-selective angiotensin II antagonist, acted weakly as a partial agonist when infused at a dose 200-fold higher than angiotensin II and effectively blocked the dipsogenic action of angiotensin II; this corresponds to the inhibition of angiotensin II-induced excitation by Sar1-Ile8-angiotensin II observed in duck subfornical organ neurons. DuP 753 (losartan), an angiotensin II antagonist specifically blocking AT1 receptors in mammals, had equivocal effects on angiotensin II-induced drinking in ducks at rates 50- and 200-fold higher than angiotensin II, which corresponds to the weak inhibitory action of this compound on angiotensin II-induced neuronal excitation in the duck SFO. Blood pressure was only marginally elevated by the applied angiotensin II dose and Sar1-Ile8-angiotensin II had no effect.

Effect of central tachykinins, alone and with angiotensin II, on drinking in pigs and goats

Central administration of the tachykinins, eledoisin or physalaemin has been reported to produce significant water intake in pigeons but inhibition of stimulated drinking in rats. In this paper it is shown that high and low doses of these two tachykinins injected centrally in two much larger species, goats and pigs, did not produce any significant drinking. Furthermore, in pigs, physalaemin, but not eledoisin, attenuated AII stimulated drinking (576 +/- 64 ml AII alone, versus 456 +/- 131 ml AII + eledoisin, not significant, and 124 +/- 89 ml AII plus physalaemin, p less than 0.01, in the same 5 pigs) and also, especially at the higher doses, induced general locomotor activation. However, in goats neither tachykinin interfered with drinking induced by central injection of 300 ng AII. These results show that in pigs and goats the tachykinins, eledoisin and physalaemin, are not effective dipsogens and that one of the possible reasons for the inhibitory action of physalaemin on AII-induced drinking may be through the general locomotor activation and not through a direct effect on the central AII system.

Dipsogenic-like and behavioural effects of bombesin administered intracerebroventricularly to sheep

Bombesin administered intracerebroventricularly both by bolus injection (3.0, 6.0, 12.5, 25.0 and 50.0 ng kg-1) and slow infusion (0.4, 0.8 and 1.6 ng kg-1 min-1 for 30 min) potently and promptly stimulated water intake in sheep. This effect was dose dependent and bombesin was slightly more potent than angiotensin II (on a molar basis); both caused behavioural alterations (scratching and licking) in treated animals. Intravenous bolus injections of bombesin at doses up to 2500 ng kg-1 did not elicit either dipsogenic-like or behavioural effects, unlike angiotensin II. The receptor antagonist of angiotensin II, saralasin, provoked drinking in sheep at doses of 18.7, 37.5 and 75.0 ng kg-1 by intracerebroventricular bolus injection. These results surprisingly revealed that bombesin, a potent inhibitor of water intake in other mammals (rats and pigs), exerted in sheep dipsogenic-like effects similar to those in pigeons and ducks.

Effect of kassinin, neurokinin A and neurokinin B on drinking behaviour in the pigeon

Intracerebroventricular (i.c.v.) injection of kassinin produced a prompt and copious drinking response at doses of 10-1000 ng/pigeon, in the absence of other behavioural alterations or of changes in core temperature. Neurokinin A and B evoked drinking, but they were respectively 10 and 100 times less potent than kassinin. Intraperitoneal injection of kassinin elicited drinking, but at doses about 1000 X larger than the i.c.v. ones. The angiotensin antagonist [Sar1, Leu8]angiotensin II did not reduce drinking induced by i.c.v. kassinin, suggesting that its effect is not due to interaction with the central renin-angiotensin system. Moreover, the effect is apparently independent of the mechanisms controlling hypovolaemic and hyperosmotic thirst since exact additivity was found in the dipsogenic response when i.c.v. kassinin was administered in the presence of a hypovolaemic (subcutaneous (s.c.), polyethylene glycol) or hyperosmotic (s.c. hypertonic NaCl) dipsogenic stimulus. The present findings show that kassinin, neurokinin A and B share with the tachykinins already tested (eledoisin, physalaemin, substance P) a common dipsogenic action in pigeons. However, marked differences exist in their dipsogenic potency. This order of potency, eledoisin = kassinin = physalaemin greater than neurokinin A = substance P greater than neurokinin B, is not consistent with the tachykinin receptor subtypes so far proposed.

The apparent dependence of salt appetite in the pigeon on endogenous angiotensin II

Blockade of endogenous angiotensin II (ANG II) biosynthesis by intramuscular administration of the angiotensin converting enzyme inhibitor captopril (1 or 10 mg/kg b.w.t.) completely suppressed salt appetite induced by sodium depletion in the pigeon. The effect was selective since captopril did not reduce deoxycorticosterone (DOCA)-induced salt appetite nor water drinking to ANG II and eledoisin. Blockade of brain ANG II receptors by pulse intracerebroventricular (pICV) injection of the ANG II receptor antagonist [Sarcosine1, isoleucine8] ANG II produced a marked, although partial, inhibition of salt appetite. The inhibition was quantitatively similar to the effectiveness of the ANG II receptor blockade, as measured by the suppression of drinking to pICV ANG II. Blockade of brain aldosterone (ALDO) receptors by pICV injections of the mineralocorticoid receptor antagonist RU-28318 did not significantly suppress depletion-induced appetite at doses that markedly reduced DOCA-induced salt appetite. These findings suggest that the pigeon might be completely dependent on ANG II for the expression of depletion-induced salt appetite. This is in contrast with what has been found in the rat, in which blockade of both ANG II and ALDO are necessary to suppress the appetite.

The role of the subfornical organ in the drinking behavior of the pigeon

Pigeons with radiofrequency lesions that damaged the subfornical organ (SFO) (n = 4) or that isolated it from adjacent structures (n = 5), but not sham-lesioned pigeons, were unresponsive to blood-borne (i.p.) ANG II (100 micrograms/pigeon) in the immediate postoperative period and for 60 days thereafter. These animals were less sensitive to hypovolemic challenge (20% PEG), but they responded normally to 24 h of water deprivation and to cellular dehydration. Despite their unresponsiveness to bloodborne ANG II, the lesioned pigeons drank normally to 10 ng of i.c.v. ANG II given as early as 10 days after surgery, and they drank reliably and vigorously but less in total volume to 100 ng i.c.v. They also drank quickly, vigorously, and in normal total volume to i.c.v. tachykinins and bombesins, and to the peripheral (i.p.) bombesins. Peripheral (i.m.) tachykinins produced only low volume and variable drinking in all birds tested regardless of brain damage. The SFO of the pigeon, like that of the mammal, is essential for drinking evoked by blood-borne ANG II and is not necessary for thirst aroused by ANG II acting from within the cerebral ventricles. Lastly, it does not mediate the dipsogenic effects of the tachykinins or the bombesins.

Central nervous system effects of peptides, 1980-1985: a cross-listing of peptides and their central actions from the first six years of the journal Peptides

A tabular synopsis is presented for articles concerned with the effects of peptides on the central nervous system that appeared in the journal Peptides from 1980-1985. A table arranged alphabetically by peptide and one arranged by effects, both listing routes of injection, species, direction of change, and qualifying notes, provides easy cross-referencing of peptides and their effects. Over 80 peptides and over 135 effects are listed. The list of peptides includes, but is not limited to: ACTH, angiotensin, bombesin, bradykinin, calcitonin, casomorphin, CCK, ceruletide, CGRP, CRF, dermorphin, DSIP, dynorphin, endorphins, enkephalins, GRF, gastrin, LHRH, litorin, metkephamid, MIF-l, motilin, MSH, NPY, NT, oxytocin, ranatensin, sauvagine, substances P and K, somatostatin, TRH, VIP, vasopressin, and vasotocin. The list of effects includes, but is not limited to: aggression, alcohol, analgesia, attention, avoidance, behavior, cardiovascular regulation, catalepsy, conditioned behavior, convulsions, dopamine binding and metabolism, discrimination, drinking, EEG, exploration, feeding, fever, gastric secretion, GI motility, grooming, learning, locomotor behavior, mating, memory, neuronal activity, open field, operant behavior, rearing, respiration, satiety, scratching, seizure, sleep, stereotypy, temperature, thermoregulation and tolerance.

Water intake modifications induced by tachykinins, bombesins and opioid peptides

Nonmammalian peptides of the tachykinin, bombesin and opioid families, injected into the brain ventricles, potently and specifically affect drinking behaviour of rats and pigeons. These peptides, or at least their counterparts, have been found in the brain of mammals and birds. It has been hypothesized that these endogenous brain peptides belong to a "brain peptidergic system" which participates in the control of water intake and body fluid homeostasis.

Neuropeptides and thirst

A number of neuropeptides have been found to affect fluid intake when injected directly into the brain of various vertebrate species. These include: angiotensin II and its peptide precursors; the tachykinins Substance P, eledoisin and physalaemin; the opioid peptides met- and leu-enkephalin and beta-endorphin; bombesin; neurotensin; and vasopressin. Some of these stimulate drinking, some inhibit water intake, and the tachykinins have opposite effects on thirst depending on the species tested. Very little is known about the site or mechamism of action of most of these peptides or if their effects on thirst are physiological. The exception is angiotensin II, a peptide hormone that is synthesized in the blood in response to hypovalaemia or hypotension and is involved in many aspects of the regulation of blood volume and pressure. Angiotensin II injected intravenously or intracranially stimulates drinking in all reptiles, birds and mammals tested. In addition to its role as a hormone, angiotensin II may also function as a neurotransmitter or neuromodulator, since all of the enzymes and precursors necessary for its synthesis have been found in the central nervous system.