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Biomedical subjects

J Antunes-Rodrigues

Publications and source records attributed to J Antunes-Rodrigues.

At least 127 records · Page 7Linked to original sources
PubMed1985

Atrial natriuretic factor inhibits dehydration- and angiotensin II-induced water intake in the conscious, unrestrained rat.

Peptides isolated from atrial extracts possess potent natriuretic and diuretic activities. In general, these peptides, called atrial natriuretic factors (ANFs), oppose the actions of the water-conservatory peptides angiotensin II and vasopressin and are released from the heart in response to atrial stretch as a consequence of increased venous return. The recent description of ANF-like immunoreactivity in brain regions associated with the control of water intake suggested a role for these peptides in the neurogenic mechanisms of thirst. Intracerebroventricular (third ventricle) infusion of 1.0 or 2.0 nmol of ANF in conscious, overnight-dehydrated rats significantly inhibited subsequent water intake over a 2-hr test period. Intravenous infusion of 2.0 nmol, but not 1.0 nmol, of ANF resulted in a similar inhibitory action, suggesting that ANF released from the heart might act centrally to inhibit water intake by an action at one or more of the circumventricular organs. Water intake induced by central infusion of angiotensin II (9.6 and 25 pmol) in normally hydrated rats was significantly inhibited by prior infusion of 2.0 nmol of ANF. Water intake induced by higher doses of angiotensin II was not altered significantly by prior infusion of ANF. These results indicate a possible physiologic role for ANF in the hypothalamic control of water intake and reveal that the cardiac peptides can act centrally, as well as peripherally, to assist in the normalization of extracellular fluid volume.

Angiotensin II↗
PubMed1985

Effect of locus ceruleus lesion on luteinizing hormone secretion under different experimental conditions.

The objective of the present study was to determine the participation of the locus ceruleus (LC) in the regulation of the estrous cycle and of luteinizing hormone (LH) release on the afternoon of proestrus and in ovariectomized rats. Lesions of the LC on the morning of proestrus blocked the preovulatory surge of LH in the afternoon of the same day. The estrous cycle became irregular and erratic after LC lesions and displayed a prolonged period of diestrus and estrus which persisted during the entire experimental period (50 days). After this period the level of LH in the afternoon of proestrus was lower in plasma and higher in the adenohypophysis. A decrease in ovarian, uterine, and adenohypophyseal weight was also observed. LC lesions in 7-day castrated rats induced a decrease in plasma LH levels 48 und 72 h later. When these lesions were made before bilateral ovariectomy, they delayed the normal increase in plasma LH levels. From the data obtained we can conclude that lesion of the LC interferes with the cyclic as well as tonic liberation of LH. A functional rearrangement of the central noradrenergic system may occur a long time after the lesion. These effects may be mediated by connections of the LC with: (1) areas whose neurons produce gonadotropin-releasing hormone; (2) areas which in some form are involved in the liberation of gonadotropins, and (3) the median eminence.

Animals↗
PubMed1985

Regulation of gonadotrophin function in hemidecorticate rats.

The present review focuses on some aspects of the regulation of gonadotrophin (LH and FSH) and prolactin secretion in rats submitted to hemidecortication (HD). The removal of rhinencephalic and cortical structures induces the following changes: Irregular and erratic estrous cycle; Increase in LH and FSH secretion in the afternoon of proestrus and after uni- or bilateral castration; When hormonal replacement therapy was administered to castrated female rats, the controls needed larger doses of estradiol benzoate (E2) to reduce LH levels than the HD animals, which suggests an increase in the sensitivity of the hypothalamus-hypophysis axis to gonadal steroid negative feedback. When HD was performed during the neonatal period (1-3 days old), an earlier onset of puberty and sexual maturation was observed in both female and male HD rats than in controls. During the puberal evolution the HD male rats showed elevation in plasma testosterone levels, an increase in the testicular response to hCG and also in the number of testicular binding sites to LH and FSH at 38-43 days (before the onset of puberty) and to prolactin (after 60 days). The results suggest that after removal of cortical and subcortical structures (HD), with predominant inhibitory influences, the hypothalamus-hypophysis becomes more sensitive to the LH and FSH releasing mechanisms.

Age Factors↗
PubMed1984

Interaction between cholinergic and osmolar stimulation of the lateral hypothalamic area (LHA) on sodium and potassium excretion.

Hypotonic and isotonic solutions into the LHA of unrestrained rats caused no alteration in renal water and electrolyte excretion. Similar results were obtained after injecting hypo, iso and hypertonic glucose solutions. On the other hand, a hypertonic NaCl solution produced an increase in natriuresis and kaliuresis immediately after being injected into the LHA. The carbachol elicited an increase in natriuresis and kaliuresis as well as a decrease in urine output in the first urine samples collected after the injection being injected into the LHA. This response was not modified when the same dose of carbachol was injected associated with NaCl or glucose solutions. The observation of a lack of summation between the effects of carbachol and hypertonic NaCl, as well as the maintenance of the natriuretic and kaliuretic effects in response of the injection of the hypertonic solution even in the presence of blocked cholinergic pathways (atropine), suggests a dissociation between the mechanisms activated by the hypertonic solution and the cholinergic stimulation of the LHA.

Animals↗
PubMed1984

Effect of cholinergic and adrenergic stimulation of the subfornical organ on water intake.

Cholinergic and adrenergic agonists and antagonists were injected directly into the subfornical organ (SFO), via implanted cannulae, and the volume of water ingested was recorded over a period of 1 hour after injection. Application of 2 nmol carbachol caused intense water intake in 100% of the animals (8.78 +/- 0.61 ml), with a very short intake latency. When the 2 nmol carbachol dose was preceded by increased doses of atropine, a progressive reduction in water intake was observed, with complete blockage of the thirst-inducing response to carbachol at the 20 nmol dose level with atropine. Followed by several doses of hexamethonium, the water intake caused by application of 2 nmol carbachol was reduced, although the response was not totally blocked. Injection of 80 nmol of nicotine had a significant thirst-inducing effect in 50% of the animals studied (1.06 +/- 0.18 ml) and increase in water intake was further reduced by application of increased doses of hexamethonium. Raising the dose levels of noradrenaline into the SFO caused an increase in water intake although to a lesser degree than was observed after carbachol injection. When the 40 nmol dose of noradrenaline was preceded by increased doses of propranolol (5 to 40 nmol), there was a gradual reduction in water intake, with total blockage at the 40 nmol dose. Application of phentolamine in doses of 10 to 80 nmol caused no reduction in water intake after 40 nmol of noradrenaline.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Histophysiological study of vasectomized rats.

An histophysiological evaluation was performed of adult rat testes 30 days after vasectomy. A higher frequency of stage VII-VIII of the tubular cycle was observed, indicating sperm accumulation. Seminiferous tubules and tubular lumen having increased diameters were also observed, but these results cannot be explained only in terms of increase in retrograde intratubular pressure. The rise in basal gonadotrophin levels as well as in testosterone levels observed under basal conditions and 30 and 60 min after stimulation with human chorionic gonadotrophin (hCG) suggested hyperactivity of the Leydig cells. The observed increased frequency of Leydig cells with smaller nuclear volumes may be correlated with higher luteinizing hormone levels. The results are discussed in terms of the possible role of neuromotor components resected during vasectomy, which may alter the spermatogenic and the secretory functions of the testis.

Animals↗
PubMed1983

Identification of pathways involved in the natriuretic, kaliuretic and diuretic responses induced by cholinergic stimulation of the medial septal area (MSA).

Natriuresis, kaliuresis and diuresis have been studied in rats following water loading and cholinergic stimulation in the MSA before and after bilateral electrolitic lesion of the habenula, or medullary stria, or supraoptic nucleus or paraventricular nucleus, or fornix. Carbachol injection in MSA elicited an increase of natriuresis and kaliuresis. These responses were blocked by bilateral electrolytic lesion of the habenula, medullary stria, or supraoptic nucleus but not of the paraventricular nucleus or the fornix. Urinary output plotted as a function of time showed antidiuresis in periods of 20 and 40 minutes after carbachol injection into the MSA. The lesion of the supraoptic nucleus inhibited this antidiuresis and natriuresis. The lesion of the habenula or medullary stria blocked natriuresis but not antidiuresis suggesting an independence between the mechanisms of antidiuretic hormone release and natriuresis regulation. The integrity of the habenula, medullary stria and supraoptic nucleus seems to be important in the mediation of the natriuretic response induced by carbachol injection into the MSA.

Animals↗
PubMed1982

Puberty and sexual maturation in hemidecorticate female rats.

The onset of puberty and sexual maturation were studied in female rats that had been hemidecorticated (HD) during the neonatal period (1-3 days old). Hemidecorticate and control rats submitted to photostimulation (14 h light: 10 h dark) had earlier and better synchronized vaginal opening (VO) than rats raised under natural light (12 h light: 12 h dark). HD rats maintained under 14 h light: 10 h dark had vaginal opening 4-5 days earlier than their controls under the same light conditions. Peaks of plasma gonadotrophin (LH) were observed in hemidecorticate animals 10 days (30th day of life) earlier than in the controls (40th day). These LH peaks were preceded by higher adenohypophyseal and uterine weights at 25 and 30 days of age. The estrous cycles observed in adult rats that were hemidecorticated during the neonatal period were similar to that of intact rats. These results suggest that hemidecortication induces early puberty. This effect could be due to accelerated maturation of the ovaries probably due to the unrestricted activity of the medial basal hypothalamus, which in turn might activate the hypothalamic mechanisms that trigger puberty.

Animals↗
PubMed1981

The control of sodium chloride intake: functional relationship between hypothalamic inhibitory areas and amygdaloid complex stimulating areas.

Sodium chloride intake was studied in rats submitted to different neurosurgical procedures. Intake decreased in animals submitted to bilateral destruction of the basolateral amygdaloid complex, and increased after the same animals were submitted to destruction of the anterior lateral hypothalamus, a procedure which is known to cause increased intake in intact rats. In the reverse experiment, where the anterior lateral hypothalamus was destroyed before the basolateral amygdaloid complex, the effect of increased sodium chloride intake induced by destruction of the hypothalamus overcame the decreased expected upon destruction of the amygdaloid complex. These results permit us to conclude that the hypothalamic areas which inhibit sodium chloride intake predominate over the stimulating areas of the amygdaloid complex in the control of sodium chloride intake.

Amygdala↗
PubMed1981

Effects of hemidecortication on the regulation of rat thyroid function.

1. Thyroid function in hemidecorticate and control rats was studied by the measurement of oxygen consumption (under basal conditions and after cold exposure) and radioiodine (131 I) uptake by the thyroid after a low-iodine diet for 30 days. 2. The oxygen uptake of male and female hemidecorticate rats under basal conditions (29 degrees C) did not differ significantly from that of the controls. The values observed for both experimental groups were relatively constant, ranging from 40 to 75 kcal h-1 m-2 for 2 to 50-day-old animals. 3. When hemidecorticate and control rats, age 60-65 days, were exposed to 7-8 degrees C for 5-6 h, the oxygen consumption of the hemidecorticate rats increased (83-84 kcal h-1 m-2) but to a lower extent than that of the controls (105-106 kcal h-1 m-2). 4. The rate of radioiodine (131 I) uptake by the thyroid gland of hemidecorticate rats was also lower than that of controls when the animals were maintained on a low-iodine diet. 5. These results show that, under basal conditions, the hypothalamic-pituitary-thyroid axis of hemidecorticate rats does not differ from that of control rats. However, when exposed to cold the hemidecorticate animals were not able to increase their oxygen consumption to the extent achieved by the control groups.

Animals↗
PubMed1980

Screening for rabbit brain neuropeptide-metabolizing peptidases. Inhibition of endopeptidase B by bradykinin potentiating peptide 9a (SQ 20881).

Neutral thiol-activated peptidases present in the pH 5-soluble fraction of rabbit brain (separated by step-elution chromatography on diethylaminoethyl cellulose) were screened for the hydrolysis of bradykinin. Lys-bradykinin, Met-Lys-bradykinin, angiotensin I, angiotensin II, substance P, luteinizing hormone-releasing hormone (LH-RH), and neurotensin by bioassay. The column effluent was monitored for bradykinin inactivation and arylamidase activity and combined in six pools on the basis of bradykinin inactivation. The pools were characterized by determining the peptide fragments and amino acids released from bradykinin with an amino acid analyzer. Pools 1 through 3 contained 80% of the kininase activity and essentially all of the endopeptidase A and B activity, whereas pools 4 through 6 accounted for 98% of the recovered arylamidase activity. Bradykinin, angiotensin I, angiotensin II, and substance P were inactivated by all the pools, whereas LH-RH and neurotensin were inactivated by pools 3 and 4, and pools 3, 4, and 5, respectively. These data show that rabbit brain contains peptidases having some selectivity for the inactivation of neuropeptides. Endopeptidase B purified from pool 3 is inhibited by bradykinin-potentiating peptide 9a (BPP9a, SQ 20881) (< Glu-Trp-Pro-Arg-Pro-Gln-Ile-Pro-Pro), a competitive inhibitor of the hydrolysis of bradykinin (Km = 3.5 X 10(-5) M, Ki = 3 X 10(-6) M) which also completely inhibits the inactivation of LH-RH.

Angiotensin I↗
PubMed1979

Influence of the subfornical organ on water intake induced by septal lesion.

Rats bearing lesions in the septal area (SA), or in the subfornical organ (SFO) or simultaneously in both regions were submitted to various thirst-eliciting procedures. The rats with hyperdipsia induced by lesion of the SA drank more water than either normal rats or SFO-lesioned animals under the same thirst-eliciting or angiotensin-liberating stimuli (polyethyleneglycol, isoproterenol, water deprivation and ligation of the inferior vena cava). The overdrinking elicited by SA lesions was blocked after SFO lesions. Neither hypovolemia, nor hypotension or water deprivation could elicit increased water intake in SFO-lesioned animals even after destruction of the SA. Animals with SFO lesions did not show increase of the water intake after cellular dehydration. The results obtained suggest that the SFO acts as the main structure in the regulation of water intake elicited by angiotensin with two opposite effects: one direct, facilitating water intake and the other indirect inhibiting the SA. The SA has an inhibitory effect on the SFO and on water intake.

Animals↗
PubMed1978

Luteinizing hormone secretion in hemidecorticate female rats under several experimental conditions.

Luteinizing hormone (LH) secretion by the anterior pituitary gland was investigated in hemidecorticate (HD) rats under several conditions. Higher plasma and lower pituitary LH levels were observed in HD rats in the afternoon of proestrus, after unilateral ovariectomy, and at the 7th and 14th days after bilateral castration. The ovarian hypertrophy observed in HD rats did not differ from control. When hormonal substitutive therapy was started 3 days after bilateral ovariectomy, larger doses of estradiol benzoate (EB) were required to reduce plasma LH levels in control than in HD animals. The increase in pituitary weight was, however, significantly higher in the HD castrated group. When substitutive therapy started at the 7th and 14th days after castration no significant differences between the 2 experimental groups were observed. The results of substitutive therapy suggest that hemidecortication induces an increase in the sensitivity of hypothalamic-pituitary axis to estrogen negative feedback. This change in sensitivity is clearly seen in HD rats during the first few days after castration. These results suggest that hemidecortication may release the hypothalamus from inhibitory influences coming from rhinencephalic or cortical structures, thus rendering the preoptic-suprachiasmatic complex (POA-SCH) more sensitive to LH-releasing mechanisms.

Animals↗
PubMed1977

Adrenergic stimulation of the lateral hypothalamic area on sodium and potassium excretion.

The effects of adrenergic stimulation of the lateral hypothalamic area on sodium and potassium excretion were studied in rats bearing implanted cannulae. When noradrenaline was injected into several points of the lateral hypothalamic area, a dose-related increase in natriuresis and kaliuresis was observed. Rats previously injected through the same cannulae with alpha (Regitine) or beta (Propranolol) blocking agents showed different natriuretic responses when injected with noradrenaline. It was observed that the normal noradrenaline-induced natriuresis was abolished by the alpha-adrenergic blockers, while beta-adrenergic blockers increased the response. Intrahypothalamic injection of Isoproterenol, and activator of the beta-adrenergic receptor, induced a decrease in natriuresis, kaliuresis and urinary volume. In contrast, injection of Metaraminol, an alpha-adrenergic agonist, caused an increase in sodium and potassium excretion and a reduction of urinary volume. Drugs blocking the destruction of noradrenaline or its reuptake by the presynaptic nerve endings potentiated 2-fold the action of 20 nmol of noradrenaline. These experiments provide good evidence for the existence of an adrenergic mechanism consisting of alpha and beta receptors which works antagonistically on the regulation of sodium and potassium excretion. The excretion on the two electrolytes is stimulated by the alpha-adrenergic system, and inhibited by the beta-adrenergic system.

Animals↗