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Biomedical subjects

A Argiolas

Publications and source records attributed to A Argiolas.

At least 73 records · Page 4Linked to original sources
PubMed1992

Prevention by morphine of apomorphine- and oxytocin-induced penile erection and yawning: site of action in the brain.

The effect of morphine administered systemically or into the paraventricular nucleus of the hypothalamus (PVN) on penile erection and yawning induced either by oxytocin or by the dopaminergic agonist apomorphine was studied in male rats. Systemic morphine (0.5 to 5 mg/kg intraperitoneally [IP]) prevented in a dose-dependent manner penile erection and yawning induced by the intracerebroventricular injection (ICV) of oxytocin (30 ng) or by the subcutaneous (SC) administration of apomorphine (80 micrograms/kg). Morphine (0.1 to 5 micrograms), but not U-69,593 (5 micrograms), injected into the PVN 10 minutes before oxytocin or apomorphine, was found to be able to prevent penile erection and yawning induced by the unilateral PVN microinjection of oxytocin (10 ng) or apomorphine (50 ng). The morphine-induced prevention of these behavioral responses was abolished by pretreatment with naloxone (3 mg/kg IP) 15 minutes before morphine. The present results suggest that morphine prevents apomorphine- and oxytocin-induced penile erection and yawning by inhibiting the activity of oxytocinergic neurons through mu-type receptors in this hypothalamic nucleus.

Analgesics↗
PubMed1991

Central functions of oxytocin.

Oxytocin, the peptide well-known for its hormonal role in parturition and lactation, is present in several extrahypothalamic brain areas besides the neurohypophyseal system. The peptide is found in neurons which send their projections to brain areas containing specific oxytocin-binding sites. Oxytocin is also released from its synapses in a calcium-dependent fashion and may be the precursor of potent behaviorally active neuropeptides. These findings suggest that this ancient neuropeptide acts as a neurotransmitter in the central nervous system. We have attempted to review the most recent behavioral, morphological, electrophysiological and neurochemical studies providing evidence that oxytocin plays an important role in the expression of central functions, such as maternal behavior, sexual behavior (penile erection, lordosis and copulatory behavior), yawning, memory and learning, tolerance and dependence mechanisms, feeding, grooming, cardiovascular regulation and thermoregulation.

Animals↗
PubMed1990

Effect of apomorphine on oxytocin concentrations in different brain areas and plasma of male rats.

The effect of the dopamine (DA) agonist, apomorphine, on oxytocin concentrations in the hypothalamus, hippocampus, septum and plasma was studied in male rats. Apomorphine dose dependently increased the concentration of oxytocin in the plasma and hippocampus, the minimal effective dose being 80 micrograms/kg s.c., which induced a 65% increase in plasma and a 45% increase in the hippocampus. The maximal effect (210 and 125% above controls) was induced with 240 micrograms/kg s.c. In contrast, there was a significant decrease (32%) in the oxytocin concentration in the hypothalamus, but only after the highest doses of apomorphine, while no change was found in the septum. The apomorphine effect in the hippocampus and hypothalamus was prevented by the mixed DA D-1/D-2 receptor blocker, haloperidol (0.3 mg/kg i.p.), and by the DA D-2 receptor blocker, (-)-sulpiride (20 mg/kg i.p.), but not by the DA D-1 receptor blocker, SCH 23390 (0.2 mg/kg s.c.). Similar effects were found in plasma, although SCH 23390 inhibited the apomorphine effect by 45%. Our results suggest that apomorphine stimulates oxytocinergic transmission in male rats and provide biochemical support for the hypothesis that a DA-oxytocin link exists in the central nervous system.

Animals↗
PubMed1990

Oxytocin-induced penile erection and yawning: role of calcium and prostaglandins.

The effect of verapamil, flunarizine, nimodipine, nicardipine, and nifedipine, calcium channel inhibitors, and of indomethacin and aspirin, inhibitors of prostaglandin synthesis, on penile erection and yawning induced by oxytocin was studied in male rats. All calcium channel inhibitors given intraperitoneally (IP) 60 min before the intracerebroventricular (ICV) injection of oxytocin (30 ng) prevented in a dose-dependent manner oxytocin effect. Nimodipine and nicardipine were the most effective being active at doses between 5 and 20 mg/kg, while the others were active at doses higher than 15 mg/kg. Prevention of oxytocin effect was also seen after ICV injection of the above compounds. Unlike calcium channel inhibitors, indomethacin given either IP (10 and 50 mg/kg) or ICV (50 micrograms), or aspirin (100 mg/kg IP) were ineffective. Microinjection of calcium, but not of prostaglandin E2 and prostaglandin F2 alpha in the paraventricular nucleus of the hypothalamus, the brain area most sensitive for the induction of the above behavioral responses by oxytocin, induced a symptomatology similar to that induced by oxytocin. The present results suggest that calcium might be the second messenger which mediates the expression of penile erection and yawning induced by oxytocin.

Animals↗
PubMed1990

Omega-conotoxin prevents apomorphine- and oxytocin-induced penile erection and yawning in male rats.

The effect of the intracerebroventricular (ICV) administration of omega-conotoxin GVIA on penile erection and yawning induced by oxytocin or by the dopaminergic agonist apomorphine was studied in male rats. The peptide toxin, 1-10 ng given ICV 5 min before oxytocin (30 ng ICV) or apomorphine (80 micrograms/kg SC), but not its carboxymethylated (CM) derivative, prevented the above behavioral responses in a dose-dependent manner. Similarly, omega-conotoxin (5 ng) unilaterally injected in the paraventricular nucleus of the hypothalamus (PVN) prevented penile erection and yawning induced by the microinjection of oxytocin (10 ng) or apomorphine (50 ng) in the PVN. omega-Conotoxin injected in the PVN, but not in the preoptic area, prevented also penile erection and yawning induced by systemic apomorphine (80 micrograms/kg SC). ICV omega-conotoxin was unable to prevent stereotypy induced by apomorphine (500 micrograms/kg SC). The present results provide further evidence that calcium plays a major role in the expression of penile erection and yawning and that apomorphine and oxytocin induce these behavioral responses by mobilizing calcium through omega-conotoxin-sensitive (N-type) calcium channels.

Animals↗
PubMed1990

Role of calcium in the expression of ACTH-induced stretching, yawning and penile erection.

The effect of omega-conotoxin GVIA, a potent and selective inhibitor of N-type calcium channels and of the organic calcium channel inhibitors nimodipine, verapamil and flunarizine, on stretching, yawning and penile erection induced by ACTH 1-24 was studied in male rats. omega-Conotoxin (1-10 ng ICV 15 min before ACTH, 10 micrograms ICV), but not carboxymethylated omega-conotoxin, induced a dose-dependent prevention of all ACTH effects. In contrast, organic calcium channel inhibitors (20 mg/kg IP 30-60 min before ACTH) failed to modify ACTH-induced stretching and yawning but induced a 25% decrease in the number of penile erection episodes induced by the peptide, and prevented, like ICV omega-conotoxin, oxytocin- and apomorphine-induced yawning and penile erection. When injected in the paraventricular nucleus of the hypothalamus, omega-conotoxin prevented the above behavioral responses induced by apomorphine and oxytocin but not by ACTH 1-24. The present results suggest that ACTH induces stretching, yawning and penile erection by mobilizing calcium through central omega-conotoxin-sensitive calcium channels in brain sites different from those sensitive to oxytocin and apomorphine.

Animals↗
PubMed1990

Effects of neonatal and adult thyroid dysfunction on thymic oxytocin.

Prenatal plus neonatal administration of methimazole (MMI), a procedure provoking marked hypothyroidism in rats, increased by about 100% the thymic content of oxytocin and severely (by approximately 80%) decreased the thymus weight, compared to euthyroid counterparts. Adult-onset, propylthiouracyl (PTU)-induced hypothyroidism, while provoking thymic involution, or thyroxine (T4) hyperthyroidism, did not affect oxytocin concentrations. Thymic involution and increases in thymus oxytoxin could also be obtained with repeated administration of the potent glucocorticoid dexamethasone. However, since corticosterone, unless subchronically injected at largely supraphysiological doses, was previously shown to have no influence on thymic parameters of young adult rats, a major involvement of the neonatal adrenal axis in oxytocin alterations could be excluded. It is suggested that the ontogenesis of thymic oxytocin production is under thyroid control.

Aging↗
PubMed1990

Correlation between amniotic levels of alpha-MSH, ACTH and beta-endorphin in late gestation and labour in normal and complicated pregnancies.

alpha-MSH, ACTH and beta-endorphin were measured by radioimmunoassay in samples of amniotic fluid collected from the 32nd to the 38th gestational week and at labour from normal pregnancies and pregnancies complicated by gestosis. In normal pregnancies, the concentration of alpha-MSH, ACTH and beta-endorphin remained relatively constant during the last 7 gestational weeks, but increased at labour above the values of the 38th week by 88, 143 and 96%, respectively. A positive correlation between beta-endorphin and alpha-MSH (r = 0.92) or ACTH (r = 0.76) levels was found when labour values were considered in the regression analysis. In contrast, when labour values were excluded, only a poor positive correlation between beta-endorphin and alpha-MSH (r = 0.52) was found. In complicated pregnancies, alpha-MSH and ACTH concentrations were similar to those found in normal pregnancies: on the other hand, the level of beta-endorphin, was found to be 130% higher than normal. As in normal pregnancies, alpha-MSH, ACTH and beta-endorphin levels increased at labour, but only by 46, 44 and 23%, respectively. In contrast to in normal pregnancies, the correlation between beta-endorphin and alpha-MSH or ACTH was not significantly modified by labour values. The present results confirm and extend previous studies showing that beta-endorphin may be considered a marker of fetal distress and that the fetal pituitary is capable of reacting to stressful stimuli in normal and suffering fetuses.

Adolescent↗
PubMed1989

Calcium channel inhibitors prevent apomorphine- and oxytocin-induced penile erection and yawning in male rats.

The effect of i.p. injection of the calcium channel inhibitors, verapamil, flunarizine, nifedipine, nimodipine and nicardipine, on penile erection and yawning induced by the dopamine agonist, apomorphine, or by oxytocin was studied in male rats. The five compounds antagonized in a dose-dependent manner the behavioral responses induced either by apomorphine or oxytocin. Nimodipine and nicardipine were found to be the most potent, being active in doses between 5 and 20 mg/kg, while nifedipine, verapamil and flunarizine were active in doses higher than 15 mg/kg. The results suggest that calcium is involved in the expression of the above-mentioned behavioural responses.

Animals↗
PubMed1989

Evidence that apomorphine induces penile erection and yawning by releasing oxytocin in the central nervous system.

Oxytocin (10 and 30 ng) injected into a lateral ventricle (i.c.v.) or the dopamine agonist apomorphine (40 and 80 micrograms/kg) injected subcutaneously induced repeated episodes of penile erection and yawning in male rats. The concomitant administration of the two substances did not produce any further increase in the number of penile erection and yawning episodes. Penile erection and yawning induced by either oxytocin or apomorphine were antagonized in a dose-dependent manner by i.c.v. pretreatment with the oxytocin antagonists [d(CH2)5Tyr(Me)-Orn8]vasotocin, [Pen1,Phe(Me)2,Thr4,Orn8]oxytocin and [d(CH2)5Tyr(Me)-Arg8]vasopressin, with a rank order of potency that follows their antioxytocic activity. (i.e. [d(CH2)5Tyr(Me)-Orn8]vasotocin congruent to [Pen1,Phe(Me)2,Thr4,Orn8]-oxytocin greater than [d(CH2)5Tyr(Me)-Arg8]vasopressin). The results suggest that apomorphine induces penile erection and yawning by releasing oxytocin in the central nervous system.

Animals↗
PubMed1989

Apomorphine increases plasma oxytocin concentration in male rats.

The effect of systemic administration of the dopamine agonist apomorphine on plasma oxytocin concentration was studied in male rats by a specific radioimmunoassay. Apomorphine given subcutaneously in doses ranging from 80 to 480 micrograms/kg increased oxytocin levels in a dose-dependent manner. The minimal effective dose was found to be 80 micrograms/kg, which induced a 66% increase above basal values, while the maximal effect (210%) was seen with a dose of 240 micrograms/kg. The apomorphine effect was prevented by pretreatment with the DA D2-receptor blockers haloperidol (0.2 mg/kg i.p.) or (-) sulpiride (10 mg/kg i.p.) and, but only partially, with the DA D1-receptor blocker SCH 23390 (0.2 mg/kg s.c.). The present results suggest that hypothalamic dopamine has a facilitatory role on the release of oxytocin in male rats.

Animals↗
PubMed1989

Oxytocin-induced penile erection and yawning in male rats: effect of neonatal monosodium glutamate and hypophysectomy.

Penile erection and yawning induced by the intracerebroventricular (ICV) injection of oxytocin (10-1000 ng) was studied in hypophysectomized rats and in rats neonatally treated with monosodium glutamate (MSG), a treatment that depletes hypothalamic opiomelanocorticotropin-derived peptides without altering their pituitary and circulating concentration. Oxytocin effect was strongly reduced by hypophysectomy, but not by neonatal MSG. Testosterone replacement (50 micrograms/kg/day for 23 days) partially reversed the effect of hypophysectomy on penile erection, but not on yawning. The present results suggest that oxytocin does not induce penile erection and yawning by releasing an ACTH-derived peptide from hypothalamic opiomelanotropinergic neurons, and that the pituitary gland exerts a permissive role on the expression of the above behavioural responses induced by oxytocin.

Animals↗
PubMed1989

Apomorphine stimulation of male copulatory behavior is prevented by the oxytocin antagonist d(CH2)5 Tyr(Me)-Orn8-vasotocin in rats.

The effect of the intracerebroventricular (ICV) injection of the oxytocin antagonist d(CH2)5Tyr(Me)-Orn8-vasotocin on the stimulation of copulatory behavior induced by the dopamine (DA) agonist apomorphine was studied in male rats. Apomorphine (80 micrograms/kg SC) given 5 min before mating tests decreased intromission frequency and ejaculation latency in experienced male rats. Such effects were abolished and reversed by pretreatment with 50 and 1000 ng of the oxytocin antagonist given ICV 5 min before apomorphine. The peptide per se markedly increased intromission and ejaculation latency and abolished ejaculation in control rats. The results suggest that brain oxytocin is implicated in the expression of sexual behavior, and apomorphine might improve male copulatory behavior by releasing oxytocin in brain.

Animals↗
PubMed1989

Oxytocin-induced motor disturbances: relationship with penile erection and yawning.

The intracerebroventricular (ICV) injection of oxytocin at doses between 5 and 100 ng induced repeated episodes of penile erection and yawning, while at doses between 100 ng and 10 micrograms it induced motor disturbances often culminating in barrel rotation in rats. The intensity of motor disturbances was inversely correlated to the number of yawning and penile erection episodes. Pretreatment with the dopaminergic agonist apomorphine (80 and 240 micrograms/kg SC) failed to modify the incidence of motor disturbance induced by high doses of oxytocin, but markedly reduced the intensity of the symptomatology in a dose-dependent manner. The present results suggest that high doses of oxytocin induce motor disturbances which mask penile erection and yawning, and that brain dopaminergic systems have a protective role against this symptomatology.

Animals↗
PubMed1988

The oxytocin antagonist d(CH2)5Tyr(Me)-Orn8-vasotocin inhibits male copulatory behaviour in rats.

The effect of an intracerebroventricular (i.c.v.) injection of the oxytocin antagonist, d(CH2)5Tyr(Me)-Orn8-vasotocin, on the copulatory behaviour of vigorous male rats in the presence of females in estrus was studied. The peptide (2.5, 25 and 50 ng, 15 min before mating tests) decreased the number of mounts and intromissions, and abolished ejaculation almost completely at all doses tested. The peptide failed to significantly influence motor activity at the doses used. The results support the hypothesis that central oxytocin plays a physiological role in the expression of copulatory behaviour.

Animals↗