A renin-like activity in pineal gland and hypophysis.

The presence and distribution of renin-like activity in hypophysis, pineal gland and some neural tissues were studies in both normal and salt-loaded rats. The Boucher micromethod was used to detect enzymatic activity. In normal rats both the pituitary and pineal glands contained significantly higher values of renin-like activity than did the other tissues examined. In salt-loaded animals there was a significant decrease of the renin-like activity of the glandular tissue while in the other brain areas the activity increased. The results are discussed in terms of the possible physiological role of the central renin-angiotensin system in the regulation of fluid and electrolyte balance.

Expression of the vasopressin and oxytocin genes in human hypothalami.

Poly(A)+ RNA isolated from post-mortem human hypothalami has been used to characterize the poly-protein precursors to vasopressin and oxytocin. Translation in a cell-free system and subsequent immuno-precipitation with antibodies raised against either vasopressin or neurophysin identified a product of Mr 19000 (prepro-vasopressin). A second less intense product of Mr 16500 was tentatively identified as prepro-oxytocin. A cDNA library derived from the human hypothalamic poly(A)+ RNA was screened for vasopressin and oxytocin-encoding cDNA using heterologous probes; clones encoding the two precursors were identified and found to be organized as their rat and bovine counterparts. Northern blot analysis shows that the mRNAs for the two prepro-hormones consist of approximately 840 (AVP) and approximately 700 (OT) nucleotides.

Evidence for the involvement of cerebral renin-angiotensin system (RAS) in stress analgesia.

Studies concerning variations of the central renin-angiotensin system (RAS) during immobilization stress in rats have shown a significant increase in renin-like activity in the hypothalamus and fronto-parietal cortex, together with a definite decrease in the hypophysis and pineal gland. The resultant stress analgesia is blocked by the previous administration of naloxone and saralasin (angiotensin II antagonist). The intracerebral administration of renin and angiotensin II produces an increase in latencies to thermoalgesic stimuli; this is reduced, as is immobilization stress, by naloxone and saralasin. Both chemical hypophysectomy obtained by dexamethasone pretreatment as well as surgical epiphysectomy block the stress-induced analgesia. The experimental data obtained argue in favour of the participation of the cerebral RAS in stress analgesia through the indirect mechanism of release of opioid peptides.

Cyclic GMP and protein kinase G inhibit the quantal transmitter release induced by protein kinase C.

Protein kinase G inhibits the spontaneous release of acetylcholine quanta at the frog neuromuscular junction as shown by the effects of H-8, a G kinase blocking agent. Moreover, the permeant dibutyryl cGMP blocked the frequency increase obtained in the presence of protein kinase C activators (diacylglycerol and phorbol ester) while the cAMP activated protein kinase A did show only an additive effect.

High levels of human chymase expression in the pineal and pituitary glands.

The brain renin-angiotensin system plays a role in both cardiovascular homeostasis and neurosecretory functions. Since the mechanisms of angiotensin (Ang) II formation in the human brain have not been clarified, the aims of the present study were to determine the presence of human chymase and angiotensin I-converting enzyme (ACE) in human and non-human brains. In the human brain, the total Ang II-forming activity was significantly higher in the pineal and pituitary glands than those in other regions. In other species (rat, bovine and porcine), the level of chymase as well as total Ang II-forming activities in pineal glands were significantly lower than those in human glands. High levels of chymase-like immunoreactivity (ir) were found in the arteriolar endothelial cells, adventitial mesenchymal cells and in parenchymal cells of the human pineal and pituitary glands while ACE-ir was mostly observed in the endothelial cells and occasionally found in parenchymal cells. Our study provides the first evidence that human chymase exists in the pineal and pituitary glands. The remarkable regional and species differences in mechanisms of Ang II formation suggest a specific role of chymase or ACE in the human brain.

Influence of angiotensin II on dog pineal serotonin content.

Intravenous infusion of angiotensin II in different concentrations for 2 h induced an increase in the serotonin contents of pineal gland, hypothalamus and brain stem in dogs. The maximal stimulatory effect was obtained with a concentration of 50 ng angiotensin II/kg body wt./min. Results are interpreted with regard to the concept of an intrinsic isorenin-angiotensin system and its implications at the level of brain nervous tissue and accessory glands. Experimental data indicating the possible existence of positive and negative feedback relationships between the brain isorenin-angiotensin system and serotonin metabolism in the pineal gland, are presented.

Adenosine effects upon the spontaneous quantal transmitter release at the frog neuromuscular junction in the presence of protein kinase C-blocking and -activating agents.

This paper gives experimental evidence involving protein kinase C (PKC) in the inhibitory effects of adenosine (ADO) upon the spontaneous transmitter release at the frog neuromuscular junction. In the presence of two PKC inhibitors--polymyxin B (5 x 10(-6) mol/l) and H-7 (10(-5) mol/l), both adenosine (5 x 10(-5) mol/l) and its stable analogue 1-PIA (5 x 10(-8) mol/l), significantly increased the rate of the spontaneous release of acetylcholine quanta. Even when PKC was activated with OAG (5 x 10(-6) mol/l) or TPA (162 x 10(-9) mol/l) and quantal release was increased greatly, ADO still inhibited release. ADO deaminase increased the PKC-induced activation of the transmitter release significantly.

Adenosine effects upon transmitter release parameters in the Mg2+-paralyzed neuro-muscular junction of frog.

The influence of adenosine upon the process of transmitter release was investigated in Mg2+-paralyzed frog neuromuscular junction by using conventional microelectrophysiological techniques and binomial statistical analysis. The statistical parameters used were: m (mean number of quanta released per impulse), p (the probability of quantal release) and n (store of quanta available for release). Adenosine decreased the mean quantal content (m) by reducing n. This effect appeared to be dependent upon the free intracellular Ca2+. The nucleoside competed with the transmitter releasing effects of ouabain and increased the amount of effective Ca2+ necessary for quantal release. It did not change the slope of release parameters modification during low-frequency facilitation. The data are discussed in terms of a physical model of release.

Trifluoperazine-sensitive activation of the spontaneous transmitter release at the frog motor endplates by low doses of procaine.

Low concentrations of procaine (10(-6)-5 X 10(-5) mol/l) induced a significant increase of the spontaneous quantal transmitter release in the neuromuscular junctions of the frog cutaneous pectoris nerve-muscle preparation. The frequency of miniature endplate potentials (mepps) was increased although their size slightly decreased probably on the account of a partial block of Na+-channels at the postsynaptic membrane. The activatory effect of pre-caine was not altered under experimental conditions known to change the Ca2+ fluxes across the nerve terminal membrane such as using a Ca2+-free Ringer, or a Ca2+-channel blocker (D600), a high K+ Ringer or, finally, a low Na+ Ringer. In the presence of caffeine no change of procaine-induced activation appeared. Trifluoperazine (TFP), in a concentration known to specifically block calmodulin, completely blocked the procaine-induced increase of mepp frequency. These data suggest that procaine presumably by way of a calmodulin-dependent mechanism is related to the free cytosolic Ca2+ equilibrium. It is possible that procaine increases the free cytosolic Ca2+ concentration by blocking an active calmodulin-dependent Ca2+ extrusion mechanism.

Possible involvement of the L-arginine-nitric oxide pathway in the modulation of stress-induced analgesia.

The possible participation of nitric oxide (NO) in pain modulation and stress analgesia was studied in adult Wistar rats. Cerebral citruline as a coproduct of NO from L-arginine increased from the mean value 5.6 +/- 0.4 nM/mg.Pt. to 8.9 +/- 0.5 nM/mg.Pt. in acute restraint stress. In high doses (50 mg/kg body weight), intraperitoneal administration of L-arginine caused a small and transient decrease of the tail-flick latencies to the thermal stimulus, without significant changes of the stress analgesia induced by restraint stress. In animals pretreated with N-nitro-L-arginine methyl ester (NAME) a progressive increase of the latency time was obtained and the increased latencies induced by acute immobilization appeared significantly potentiated. These results offer new indirect evidence in favour of the modulatory role of NO in thermoalgesic sensitivity and stress-induced analgesia.

Actual data concerning the brain--immune system interface.

After a brief presentation of the immune system as sensorial and effector organ, which recognizes and defends against cellular aggressions, the main psycho-neuro-endocrine components of immune reaction regulation and modulation will be shown. Both central nervous structures that control the hormonal emissions, the vegetative innervation of the lymphoid organs as well as the afferent neurohumoral pathways involved in the making of the self-regulating and neuromodulating circuits of the humoral and cellular immune responses will be mentioned. An important position will be held by the interrelations between the hypothalamus-pituitary-corticoadrenal gland, the sympathetic-parasympathetic efferent pathways and the chemical messengers (hormones, neurotransmitters, interleukins, neurotrophins) which make possible the bi-directional neuroimmune communication for maintaining the homeostatic balances on this third effector pathway, too. Also will be presented experimental proof concerning the ability of central neurons to secrete neuromodulator cytokines and the presence of specific receptors for the various neuroactive molecules within lymphoid organs and circulating lymphocytes. To close, the psychoemotional components of the neuro-immunomodulator circuits will be mentioned, using as examples the changes induced by stress generally and oxidative stress in particular.

[The ocular hypotonic effect induced by an angiotensin-converting enzyme inhibitor (captopril)]. / Efectul hipotonizant ocular indus de un inhibitor al enzimei de conversie a angiotensinei (Captopril).

UNLABELLED: The investigation aims at analysing in healthy and glaucoma subjects the effects of an angiotensin conversion enzyme inhibitor (Captopril) on intraocular pressure, local tolerance, influence on systemic circulation and to ascertain (or suggest) the mechanisms inducing this pressure lowering. The study is prospective, masked, in acute test (10 days) and includes a series of 14 healthy subjects and 18 patients with open angle primitive glaucoma. Following numerous experimental and clinical tests, Captopril isotonic solution 2.5% administered in ocular instillation 4 times/day proved to be the most appropriate. RESULTS: Captopril solution 2.5% lowers intraocular pressure both in the normal subjects (average relief of 6.5 mm Hg) and in the glaucoma patients (8.9 mm Hg); hypotonic effects lasts for 6-8 hours; local tolerance is good; has no influence on systemic arterial pressure; tonography with constant Pt shows a 12% increase of C (insufficient to explain such a relief in intraocular pressure). The hypotesis that pressure lowering occurs (partially) by the stimulation of prostaglandin activity and consequently by improved uveoscleral drainage is suggested. CONCLUSIONS: Captopril solution 2.5% administered topically lowers intraocular pressure without adversely influencing systemic and local circulation; local tolerance is good; the mechanisms of ocular hypotonizing effect are unknown.

Antioxidant activity in rat models of nociceptive stress.

UNLABELLED: Pain is an important problem and has been the subject of many studies in recent years. MATERIAL AND METHOD: The present study has investigated the response of the antioxidant defense systems in contention stress, which mimics nociceptive stress. Contention stress was made by immobilizing the rat, Wistar rats, on an operating table in a specific position with paws tied, for thirty minutes. The determinations evaluate the levels of oxidative stress markers like reduced glutathione (GSH) and malondialdehyde (MDA) and the levels of the protecting enzymes against of free radicals in brain. RESULTS: After the application of contention stress, GSH level increased insignificantly, while MDA level increased significantly compared with the normal animals. These have demonstrated that in our model of nociceptive stress actioned the mechanisms of membrane lipid peroxidation. The activity of the antioxidant enzymes GSH, GPX and SOD decreased in the stressed animals compared with the normal group. This experiment has revealed that in our model of nociception stress, many reactive oxygen species (ROS) were generated, which reduced the enzymatic defense mechanisms and activated lipid peroxidation mechanisms.

Relaxing effects of adrenomedullin in rat mesenteric resistance arteries.

UNLABELLED: Exogenous adrenomedullin (ADM) is hypotensive in very small doses, through direct vasodilation of resistance arteries. In different region this is variably mediated by ADM and CGRP receptors. Mechanisms involve ADM effects upon smooth muscle to increase cAMP and to activate K+ channels, plus stimulation of endothelial NO release and inhibition of sympathetic noradrenaline release. AIM: We studied the mechanism of the vasodilator effect of ADM in vitro. METHOD: Rat mesenteric resistance arteries (RMRA) in isometric conditions, were stimulated using four contracting agents: K+ 40 microM, phenylephrine 10 mM, PGF2alpha 10 microM, angiotensin II 1 microM. We used methylene blue 10 microM to examine the involvement of soluble guanylate cyclase (GC) in the relaxation induced by ADM. RESULTS: We found that relaxation induced by ADM is endothelium-independent, similar regardless of the contracting agent (including high K+), and partially sensitive to methylene blue. CONCLUSIONS: K+ channel activation by ADM is not essential for relaxation. Opposite to other authors, we suggest that ADM-induced vasodilation may involve endothelium-independent activation of soluble GC.

Biosynthesis and physio-pharmacological actions of angiotensin peptides: 1. Synthetic enzymes.

The present work introduces a brief review of the actual knowledge concerning the enzymes involved in the biosynthesis of the active angiotensins, followed by a presentation of their main physio-pharmacological actions. The enzymatic pathways that generate active ang. II (1-8) are complemented with data concerning its transformation into angiotensin III (2-8), ang. IV (3-8), ang. V (1-5) and ang. 1-7. Besides the classic renin of renal origin, the tissue isorenins, represented by tonin and cathepsins D and G, inactive angiotensin-I-forming are also reviewed. Furthermore, chymase and the new angiotensin-converting enzyme 2 (ACE2), which generates angiotensin 1-7, having opposite properties from the mother-substance (Ang. II) are discussed at length. The presentation of properties of angiotensin-generating enzymes is followed by the presentation of the action of angiotensinases (aminopetidases, carboxypeptidase and endopeptidases), which are involved both in the generation of biologically active angiotensin peptides and in their inactivation.

Biosynthesis and physio-pharmacological actions of angiotensin peptides: 2. Physio-pharmacological properties.

The classic concept of the renin-angiotensin system being substantially accomplished by the new cognitive and applicative acquisitions, a natural reconsideration and completion is imposed. In consequence, ample referrals are made to the main central and peripheral actions of Angiotensins through specific receptors. Emphasis is given to the effects of Angiotensin IV and Angiotensin 1-7 which are different of those of Angiotensin II, underlining their possible role as counteracting factors to its actions, in order to remove the imbalances created by the predominating stimulation of vasoconstricting AT, receptors. There are also taken into account the mainly central neural actions of Angiotensin IV, while Angiotensin 1-7 seems to be active only in the periphery. At the end are mentioned the results of our own research on the vasodilating effects of Angiotensin 1-7 and its interrelations with Angiotensin II. New experimental proofs are brought both in favor of the endocrine, paracrine and autocrine role of the circulating and tissue renin-Angiotensin system and of the counteracting of the effects of Angiotensin II by a part of its metabolism products.

Experimental evidence on pineal renin-angiotensin system as activator of serotonin and melatonin synthesis.

Intravenous infusion of angiotensin II in quasi-physiological concentrations for two hours induced an increase in serotonin and N-acetyltransferase content of pineal gland in dogs and rats. Results are interpreted with regard to the concept of the activating role of the pineal renin-angiotensin system on the serotonin and melatonin biosynthesis.

[New data about neuroimmunomodulation and its functional implications]. / Date noi privind neuroimunomodularea si implicatiile ei functionale.

After a brief presentation of the immune system as sensorial and effector organ, which recognizes and defends against cellular aggressions, the main psychoneuroendocrine components of immune reaction regulation and modulation are shown. Both central nervous structures that control the hormonal emissions, the vegetative innervation of the lymphoid organs as wells as the afferent neurohumoral pathways involved in the making of the self-regulating and neuromodulating circuits of the humoral and cellular immune responses are mentioned. An important position is held by the interrelations between the hypothalamus-pituitary-corticoadrenal gland, the sympathetic-parasympathetic efferent pathways and the chemical messengers (hormones, neurotransmitters, interleukins, neurotrophins) which make possible the bi-directional neuroimmune communication for maintaining the homeostatic balances on this third effector pathway, too. Also experimental proof concerning the ability of central neurons to secrete neuromodulator cytokines and the presence of specific receptors for the various neuroactive molecules within lymphoid organs and circulating lymphocytes are presented. To close, the psychoemotional components of the neuroimmunomodulator circuits are mentioned, using as examples the changes induced by stress generally and oxidative stress in particular.