Biomedical subjects

P Marrama

Publications and source records attributed to P Marrama.

At least 19 recordsLinked to original sources

PubMed1998

Acute estradiol and progesterone administration reduced cardiovascular and catecholamine responses to mental stress in menopausal women.

Steroid hormones are involved in the regulation of sympathoadrenal activity. Since the effect of sex steroids on the cardiovascular system and catecholamine secretion could also be exerted through an acute, nongenomic mechanism, we have studied the response to mental stress (color word test, CWT) in a group of 15 menopausal women during estrogen (100 microg of estradiol by patch), progesterone (100 mg i.m.) or placebo administration. Systolic blood pressure (SBP) increased during CWT in the three sessions (F = 11.0, p < 0.001) but the area under the curve of SBP was higher during placebo (2,855 +/- 131 mm Hg x min) than during estradiol (2,585 +/- 139 mm Hg x min) and progesterone (2,553 +/- 179 mm Hg x min, p < 0.05 for both). Plasma epinephrine increased during CWT in the three sessions (F = 31.1, p < 0.001) and the plasma epinephrine response to mental stress was higher during placebo than during estradiol administration (F = 4.3, p < 0.01). The area under the curve of epinephrine was 10,342 +/- 1,348 pmol/min x 1 during placebo and 7,280 +/- 818 pmol/min x 1 during estradiol (p < 0.03). The plasma glycerol levels at the end of CWT were higher during placebo (0.26 +/- 0.04 nmol/l) than during estradiol (0.19 +/- 0.03 mmol/l) and progesterone (0.17 +/- 0.04 mmol/l) administration (p < 0.05 for both). No significant differences were found in the responses of diastolic blood pressure, heart rate, norepinephrine and cortisol to mental stress during placebo and estradiol or progesterone administration. This study demonstrates that acute steroid administration is able to modify the cardiovascular and catecholamine response to mental stress in menopausal women.

Adrenal Glands↗

PubMed1997

Alpha-2 adrenergic activity in perimenopausal women.

Lipid alterations and increased blood pressure may occur during perimenopause. No data are available in perimenopausal women on the alpha-2 adrenergic activity which affects norepinephrine secretion. We studied cardiovascular and catecholamine responses to clonidine (300 mg per os) in a group of 15 perimenopausal women (PeriMW) and in a control group of 13 premenopausal women (PreMW). Nine of the perimenopausal women were also studied after 4-month percutaneous estrogen replacement therapy (PeriMWE). Systolic and diastolic blood pressure (SBP, DBP), heart rate (HR), plasma norepinephrine (NE) and epinephrine (E) were evaluated before and at 120 min, 130 min, 140 min after clonidine administration. Basal values of SBP, DBP and HR were not different (F = 0.7, p = NS; F = 0.2, p = NS and F = 0.1, p = NS respectively) between PeriMW both before and after therapy and PreMW. Resting levels of E were similar in PreMW and in PeriMW before and during estrogen therapy (F = 0.8, p = NS); PeriMW showed higher basal NE levels both before and during estrogen therapy than PreMW (F = 12; p < 0.001). Clonidine administration decreased SBP, DBP and NE levels in PreMW, in PeriMW and in PeriMWE without any difference between the groups (F = 1.2, p = NS; F = 0.5, p = NS and F = 1.3, P = NS respectively). HR decreased significantly after clonidine in PreMW (F = 5.4, p < 0.03) but not in PeriMW before (F = 1.0, p = NS) and during estrogen therapy (F = 0.5, p = NS). Clonidine did not affect plasma E in the three groups studied (F = 2.8, p = NS; F = 2.2, P = NS and F = 0.1, p = NS). The present study demonstrates that increased basal plasma NE levels are present in PeriMW. The cardiovascular and catecholamine response to clonidine in PeriMW both before and during estrogen therapy are similar to those observed in PreMW, suggesting a normal inhibitory alpha-2 receptor pathway.

Adrenergic alpha-Agonists↗

PubMed1997

Cholinergic enhancement by pyridostigmine increases the insulin response to glucose load in obese patients but not in normal subjects.

OBJECTIVE: To further investigate the role, if any, of acetylcholine and the parasympathetic nervous system in modulating beta-cell secretion in man. DESIGN: Oral glucose load (OGTT, 100 g p.o. at 0 min) alone and preceded by pyridostigmine (PD, 120 mg p.o., 60 min before OGTT), a cholinesterase inhibitor, were administered on two different occasions, in random order, two or three days apart. SUBJECTS: Ten women with central obesity (OB, body mass index (BMI): 34.2 +/- 2.1 kg/m2, waist to hip ratio (WHR): 0.83 +/- 0.01, aged 39.0 +/- 5.3y) and six normal women (NS, BMI: 22.7 +/- 1.9 kg/m2, WHR: 0.74 +/- 0.01, aged 37.1 +/- 4.8y) were studied. MEASUREMENTS: Serum insulin, plasma glucose and plasma noradrenaline (NA) were measured at -60, -15 and 0 min, and then every 15 min up to +120 min. Insulin concentrations were measured in duplicate by immunoradiometric assay, glucose by glucose oxidase colorimetric method and NA was assayed after extraction with alumina using high performance liquid chromatography with electrochemical detection. Pulse rate (PR), systolic (SBP) and diastolic blood pressure (DBP) were also measured every 15 min during the tests by an automated cuff device. RESULTS: OGTT raised glucose concentrations in OB and NS (incremental area: 420 +/- 44 vs 288 +/- 70 mmol/l. 2 h, respectively) without significant differences between groups (F = 0.6, P = ns). On the other hand, OB showed an insulin response to OGTT higher than NS (10,120 +/- 1074 vs 6692 +/- 1962 microU ml-1 2 h, respectively P < 0.01). After OGTT alone NA concentrations increased to the same extent in NS (peak vs basal: 1.40 +/- 0.16 vs 1.07 +/- 0.10 nmol/l, P < 0.05) and in OB (peak vs basal: 1.50 +/- 0.14 vs 1.04 +/- 0.18 nmol/l P < 0.05). Both in NS and in OB, PD administration failed to modify basal glucose and insulin (P = ns for both) as well as basal NA concentrations. In NS, the combined administration of PD and OGTT did not modify glucose and insulin responses compared to OGTT alone 335 +/- 65.4 mmol/l. 2h and 6348 +/- 1348 microU ml-1 2h, respectively) while in OB, PD significantly increased the insulin response to OGTT (14640 +/- 3030 microU ml-1 2h, P < 0.03), while the glucose response was not significantly different from OGTT alone (478 +/- 45 mmol/l. 2h). PD administration did not modify the NA response to OGTT, in NS or OB (P = ns). In both groups, pyridostigmine administration did not affect systolic or diastolic blood pressures, but decreased pulse rate to the same extent in NS (74 +/- 2 vs 66 +/- 2 beats/min, P < 0.05) and in OB (72 +/- 1 vs 67 +/- 2 beats/min, P < 0.05). CONCLUSIONS: Our present data indicate that in man, as in animals, acetylcholine has a stimulatory influence on insulin secretion.

Abdomen↗

PubMed1996

The effects of clonidine on blood pressure, catecholamine and growth hormone release in hypogonadal men is preserved and not influenced by testosterone replacement therapy.

It has been demonstrated that castration impairs the hypotensive effect of clonidine in rat as well as its GH-releasing activity while testosterone replacement restores to normal the effects of alpha-2 adrenoceptor activation. Thus, these data point to main role of the gonadal steroid testosterone in modulating the effects of alpha-2 adrenergic activation on blood pressure, catecholamine and GH release in animal. Aim of the present study was to verify the activity of clonidine on blood pressure, catecholamine and GH release in human male hypogonadism before and after testosterone replacement. To this goal, 14 hypogonadal men (HP, age 33.8 +/- 2.9 yr; BMI < 25 kg/m2; 8 with hypergonadotropic and 6 with hypogonadotropic hypogonadism) received clonidine administration (CLON, 300 micrograms po at 0 min) before and after 3 months of testosterone replacement (testosterone propionate depot, 250 mg i.m. every 21 days). Ten normal adult volunteers (NS, age 31.5 +/- 1.9 yr; BMI < 25 kg/m2) were studied as control group. In all subjects, before and after clonidine administration, systolic and diastolic blood pressure (SBP and DBP), pulse rate (PR), norepinephrine (NE), epinephrine (E) and GH levels were recorded. In HP basal testosterone levels were lower than those in NS (1.25 +/- 0.3 vs 7.34 +/- 1.5 ng/ml, p < 0.05) and were restored to normal by hormonal replacement (6.91 +/- 1.3 ng/mL) in HP, both SBP and DBP as well as PR were normal in basal conditions and were not modified by testosterone replacement. Both before and during testosterone CLON lowered SBP, DBP and PR in HP to the same extent observed in NS. In HP, basal NE levels were lower than those in NS (0.85 +/- 0.15 vs 1.28 +/- 0.19 nmol/l, p < 0.05) and were restored to normal during testosterone replacement (1.25 +/- 0.13 nmol/l). On the other hand, basal E levels in HP were similar to those in NS (179 +/- 42 vs 197 +/- 38 pmol/l) and were not modified by testosterone therapy (167 +/- 28 pmol/l). In HP, both before and during testosterone replacement, CLON reduced NE (0.44 +/- 0.10 and 0.58 +/- 0.07 nmol/l) levels to the same levels recorded in NS (0.68 +/- 0.08 nmol/l). Basal GH and IGF-I levels in HP (1.15 +/- 0.5 and 234 +/- 42 micrograms/l, respectively) were similar to those in NS (1.18 +/- 0.4 and 221 +/- 38 micrograms/l, respectively) and were not modified by testosterone (1.35 +/- 0.6 and 256 +/- 32 micrograms/l, respectively). CLON administration induced a clear GH response in HP (F = 37; p < 0.001) which overlapped with that recorded in NS and was not modified by testosterone (F = 1.7; P = NS). Our present findings demonstrate that, differently from in animal, in man testosterone has no role in modulating the effects of alpha-2 adrenergic activation by clonidine on blood pressure, catecholamine and GH release. On the other hand, our data suggest the existence in male hypogonadism of a reduced basal noradrenergic activity which is restored by testosterone replacement.

Adult↗

PubMed1996

Prolactin and testosterone: their role in male sexual function.

The role of androgens in the sexuality of men is still not completely clear. Men with severe hyperprolactinaemia frequently show mild hypogonadism, and many complain of loss of libido and penile erectile dysfunction (ED). We studied the night-sleep related erections and the penile response to visual erotic stimuli (VES) in 44 men: 13 with severe hypogonadism (Group 1; serum testosterone < 1.4 ng/ml), 10 with mild hypogonadism (Group 2; serum testosterone 2-3.5 ng/ml), nine with severe hyperprolactinaemia and mild hypogonadism (Group 3) and 12 control men (Group 4). All of the patients complained of loss of libido and ED. Group 1 showed significantly impaired night erections when compared with any of the other three groups, but no differences were detected between Groups 2, 3 and 4. The penile response to VES did not show any significant difference between the four groups, but was lower in Group 1 than in Group 4. These data confirm that night erections are androgen-dependent, but also suggest that there are two thresholds for serum testosterone: one below which sexual behaviour is impaired with normal night erections, and a lower threshold below which night erections are also impaired. The penile response to VES was confirmed as being only partially androgen-independent. Furthermore, hyperprolactinaemia does not affect night erections or the penile response to VES, suggesting that its effect on libido and sexual behaviour is due mainly to modulation of the psychological pattern of the patient.

Adult↗

PubMed1996

Increased cardiovascular response to caffeine in perimenopausal women before and during estrogen therapy.

Perimenopause and menopause may be associated with an increased risk of cardiovascular disease, so we have investigated the cardiovascular and catecholamine response to caffeine in perimenopausal women compared to young cycling premenopausal subjects. Caffeine (250 mg per os) was administered to nine perimenopausal women and nine premenopausal women. The perimenopausal women repeated the test after 4 months of percutaneous estrogen replacement therapy. Systolic and diastolic blood pressure, pulse rate, plasma norepinephrine, epinephrine, glucose, insulin and free fatty acids were determined at 0, 15, 30, 45, 60, 90 and 120 min after caffeine administration. No differences were found in the basal values of systolic blood pressure, diastolic blood pressure, pulse rate, norepinephrine, epinephrine, insulin, glucose and free fatty acids between perimenopausal women, both before and after therapy, and premenopausal women. Caffeine induced a higher increase of systolic (F = 4.9; p < 0.05) and diastolic blood pressure (F = 4.7; p < 0.05) in perimenopausal women before and during estrogen therapy as compared with premenopausal women. Pulse rate increased significantly only in perimenopausal women before therapy (F = 6.5; p < 0.03). These data show that perimenopause either before or during short-term estrogen therapy is associated with enhanced cardiovascular reactivity to caffeine. This phenomenon is not due to increased adrenergic and metabolic responses.

Adult↗

PubMed1995

Changes in glucocorticoid receptor immunoreactivity after adrenalectomy and corticosterone treatment in the rat testis.

The distribution of glucocorticoid receptor (GR) in the rat testis was investigated by means of immunocytochemistry (IR) and computer-assisted image analysis. A monoclonal antibody against rat liver GR showed the presence of GR IR selectively in the nuclei of interstitial and tubular cells. The semiquantitative microdensitometry of GR IR revealed that 77% of the specific staining was localized in the tubular compartment of rat testis. After adrenalectomy, GR IR was greatly reduced both in interstitial and tubular cells, roughly at the same degree. Corticosterone treatment (50 mg/kg, for 5 d) of adrenalectomized animals yielded a recovery of nuclear immunopositivity without changing the cellular distribution of GR, as observed in control rats. Nevertheless, the high dose of corticosterone administered produced a significant (p < 0.01) decrease of GR IR with respect to control rats. These results provide evidence for a prevalent nuclear binding of GR in the tubular compartment in basal conditions. On the other hand, adrenalectomy or repeated corticosterone treatment seem to affect GR similarly in all positive cells without changing significantly the proportion of GR IR in the different testicular compartments. This uneven distribution of GR IR suggests that tubular cells can be a major target of corticosterone when affecting directly testicular functions in the rat.

Adrenalectomy↗

PubMed1995

Effect of testosterone replacement therapy on the somatotrope responsiveness to GHRH alone or combined with pyridostigmine and on sympathoadrenal activity in patients with hypogonadism.

There is evidence suggesting that androgens influence GH secretion in man. Our aim was to verify whether the GH releasable pool is preserved and influenced by testosterone replacement in male hypogonadism. To this goal, in eight male hypogonadal patients (HP, age 32.2 +/- 5.0 yr; Body Mass Index 23.9 +/- 1.1 kg/m2) before and after 3 months testosterone therapy, we studied the GH response to GHRH (1 microgram/kg iv) alone and combined with pyridostigmine (PD, 120 mg po), a cholinesterase inhibitor which likely inhibits hypothalamic somatostatin release allowing exploration of the maximal somatotrope secretory pool. Sixteen normal subjects (NS, age 30.1 +/- 3.5 yr; Body Mass Index 22.5 +/- 1.8 kg/m2) were studied as controls. The GH response to GHRH in HP was similar to that in NS (AUC, mean +/- SE: 1238 +/- 362 vs 1018 +/- 182 micrograms/L/h). PD potentiated to the same extent the GH response to GHRH in both groups (2092 +/- 807 and 2840 +/- 356 micrograms/L/h). After three month testosterone therapy, in HP the GH responses to GHRH alone (1352 +/- 612 micrograms/L/h) and combined with PD (1948 +/- 616 microgram/L/h) were unchanged. Also IGF-I levels in HP were similar to those in NS (222 +/- 42 vs 210.6 +/- 55.8 micrograms/L) and were unchanged during testosterone replacement (280 +/- 31 micrograms/L). As androgens have been reported to modulate sympathoadrenal activity in the rat, both before and during testosterone replacement, we also measured plasma catecholamine levels. Basal NE (p < 0.05) but not E levels were lower in HP than in NS; testosterone restored basal NE levels to normal without affecting basal E. delta absolute increase of NE and E (p < 0.05 and 0.01 vs baseline, respectively) after PD in HP were similar to those in NS and were unchanged during testosterone replacement. In conclusion, these results demonstrate that the GH releasable pool is preserved in male hypogonadism. As in this condition a reduction of spontaneous GH secretion has been reported, it could be due to neurosecretory dysfunction but not to pituitary impairment. Subtle alterations of sympathoadrenal activity seem to be present in male hypogonadism and reversed by testosterone replacement.

Adrenal Glands↗

PubMed1995

The effects of testosterone replacement on nocturnal penile tumescence and rigidity and erectile response to visual erotic stimuli in hypogonadal men.

Nocturnal penile tumescence (NPT) and erectile response to visual erotic stimuli (VES) were measured, by means of a Rigiscan device, in nine hypogonadal men, and repeated after 3 months of androgen replacement. The same assessments were carried out once in 12 eugonadal controls. The number of satisfactory NPT responses, in terms of both circumference increase and rigidity, were less in the hypogonadal men than the controls and were significantly increased by androgen replacement, confirming the results of earlier studies. In terms of circumference increase, erectile response to VES did not differ between the hypogonadal men and the controls, and did not increase with androgen replacement. In terms of rigidity, the erectile response to VES did not differ between hypogonadal men and controls. However, in terms of both duration and maximum level of rigidity, there was a significant increase following androgen replacement in the hypogonadal men. These new findings, in relation to rigidity, require a modification of the earlier formulation, which saw NPT as androgen dependent and erectile response to VES as androgen independent. NPT, and possibly spontaneous erections at other times, clearly involve an androgen sensitive system. Erectile response to VES predominantly involves an androgen independent system but may also be influenced by androgen sensitive mechanisms.

Adult↗

PubMed1995

Temporal changes in sulphated glycoprotein-2 (clusterin) and ornithine decarboxylase mRNA levels in the rat testis after ethane-dimethane sulphonate-induced degeneration of Leydig cells.

Short- (3-24 h) and long-term (4-50 days) changes in sulphated glycoprotein-2 (SGP-2) and ornithine decarboxylase (ODC) mRNA levels in the adult rat testis were studied following a single dose of ethane-dimethane sulphonate (EDS), to destroy the Leydig cells. Distribution patterns of SGP-2 and ODC labelling were consistent with prevailing expression of the two transcripts in Sertoli cells and germ cells, respectively. This pattern did not show appreciable changes following EDS administration. No labelling of SGP-2 mRNA was noted in the interstitium of control and EDS-treated rats. This finding indicates that Leydig cell death induced by EDS is not associated with increased SGP-2 mRNA levels, a phenomenon related to apoptotic cell death in many tissues. Semi-quantitative densitometric analysis of the preparations demonstrated differential changes in SGP-2 and ODC mRNA levels in the tubular compartment following EDS treatment. At 6, but not at 3 and 12, h following EDS administration, SGP-2 mRNA levels showed a significant increase, possibly secondary to a direct effect of the alkylating agent on Sertoli cells. A significant decrease in ODC mRNA levels was observed from day 7 to day 28, matching degenerative changes in the seminiferous epithelium. In contrast, a decrease in SGP-2 transcript levels was observed from days 21-35 after treatment. In conclusion, our findings demonstrate that SGP-2 mRNA, a putative marker of apoptosis, is not altered in the testicular interstitium during EDS-induced degeneration of Leydig cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Apoptosis and spermatogenesis: evidence from an in vivo model of testosterone withdrawal in the adult rat.

The seminiferous epithelium is a highly proliferating tissue in which germ cell "degeneration" is a constant feature. Recent data based on morphological analysis have shown that spontaneously dying germ cells display some characteristics of apoptosis. In order to evaluate the molecular signals controlling the phenomenon, adult male rats were studied after in vivo treatment with ethane dimethane sulphonate, an agent which leads to testosterone withdrawal by a selective destruction of Leydig cells. DNA fragmentation by agarose gel electrophoresis and cell DNA content by flow cytometry after propidium iodide staining were used to evaluate and quantify apoptosis in the testis. Despite the simultaneous presence of cells with different ploidies, the present data suggest that testosterone withdrawal induces death by apoptosis and that this phenomenon is particularly evident in haploid germ cells. Thus, this study support the involvement of testosterone in regulating programmed cell death, beside cell proliferation and differentiation, during spermatogenesis.

Animals↗

PubMed1994

Alpha 2-adrenergic activity is normal in patients with thyroid disease.

OBJECTIVE: Several studies indicate an inverse relationship between the sympathetic nervous system activity and thyroid function. Altered adrenoceptor sensitivity, particularly alpha 1 and beta, have been described in hypothyroid and hyperthyroid patients. No information in patients with thyroid disease is available on the main mechanism regulating sympathetic nervous system outflow, i.e. the alpha 2-adrenoceptor pathway. In our study we evaluated alpha 2-adrenergic activity in patients with thyroid disease by the assessment of cardiovascular and catecholamine response to clonidine, a central alpha 2 adrenergic agonist. PATIENTS: Ten patients with hypothyroidism, six patients with hyperthyroidism before and during adequate therapy, and ten healthy subjects. MEASUREMENTS: After three blood samples for the basal determination of noradrenaline and adrenaline, the subjects swallowed 4 micrograms/kg body weight of clonidine. Blood pressure and pulse rate were measured 30, 60, 90, 120, 130 and 140 minutes after clonidine administration; blood samples for determination of catecholamines were drawn at 120, 130 and 140 minutes. RESULTS: At presentation the decrease in plasma noradrenaline after clonidine in the patients was similar to that of the control group (hypothyroids: 1.07 +/- 0.23 nmol/l mean +/- SEM; hyperthyroids: 0.54 +/- 0.06 nmol/l; controls; 0.36 +/- 0.10 nmol/l; F = 1.2, P = NS). No differences were detected in the fall in adrenaline and mean arterial pressure (MAP) after clonidine. The adequate therapy induced in hypothyroid patients a decrease in the basal levels of noradrenaline (1.88 +/- 0.28 vs 0.67 +/- 0.10 nmol/l; P < 0.05) and a lesser fall in mean arterial pressure after clonidine (delta MAP 20.4 +/- 2.0 vs 9.7 +/- 2.8 mmHg; P < 0.05). No variations were detected in hyperthyroid patients after therapy either in basal hormones levels or in the magnitude of decrement in MAP and noradrenaline induced by clonidine. CONCLUSIONS: We conclude that in spite of the previously reported abnormalities in alpha 1 and beta-adrenergic receptor activity, the inhibitory alpha 2-receptor pathway is normal in patients with altered thyroid function.

Adult↗

PubMed1994

Effect of estradiol on the sympathoadrenal response to mental stress in normal men.

It has been shown that steroid hormones are able to influence the sympathoadrenal system activity. Therefore, we have investigated in a double blind cross-over study the effect of percutaneous estradiol administration (100 micrograms) on the sympathoadrenal and cardiovascular responses to mental arithmetic stress in 20 normal young males. The plasma estradiol level was 154 +/- 14 pmol/L during the estrogen session (ES) and 44 +/- 7 pmol/L during the placebo session (PL; P < 0.001). The mental stress induced a significant increase in systolic blood pressure during both the PL (F = 7.2; P < 0.001) and the ES (F = 4.8; P < 0.01); the peak obtained during PL was, however, higher than that during ES (128 +/- 2 vs. 122 +/- 3 mm Hg; P < 0.02). A significant increase in pulse rate was observed during PL (F = 4.2; P < 0.002), but not during ES (F = 2.6; P = 0.47), with the peak pulse rate being higher during mental stress in the PL than the ES (78 +/- 2 vs. 74 +/- 2 beats/min; P < 0.03). In response to the mental stress, plasma epinephrine increased significantly during PL (F = 3.2; P < 0.03), but not during ES (F = 1.1; P = 0.3). The stress-induced peak in plasma epinephrine during PL was higher than that during ES when expressed as the absolute value or the incremental peak (513 +/- 103 vs. 125 +/- 32 pmol/L; P < 0.005). The incremental peak in plasma norepinephrine obtained during PL was higher than that during ES (0.78 +/- 0.1 vs. 0.27 +/- 0.07 nmol/L; P < 0.02). Plasma free fatty acid, acetoacetate, and 3-hydroxybutyrate increased significantly from basal values during PL, but not during ES. These data show that mildly elevated levels of estradiol are able to influence the response of the adrenal medulla to mental stress in men.

3-Hydroxybutyric Acid↗

PubMed1994

Plasma catecholamines after thyrotropin-releasing hormone administration in hypothyroid patients before and during therapy.

In order to investigate sympathoadrenal activity in hypothyroidism we studied the cardiovascular and catecholamine responses to thyrotropin-releasing hormone (TRH) infusion in nine hypothyroid patients before and during adequate therapy and in seven healthy subjects. We evaluated mean arterial pressure, heart rate, plasma epinephrine and norepinephrine levels after TRH administration (200 micrograms iv) in the three groups. Mean arterial pressure, heart rate and plasma epinephrine levels were not different in the three groups and did not change after TRH administration. Hypothyroid subjects showed increased plasma norepinephrine levels (1.48 +/- 0.15 nmol/l), which were reduced after euthyroidism was reached (0.84 +/- 0.11 nmol/l) (p < 0.01). An exaggerated response of norepinephrine to TRH was observed in hypothyroid patients before therapy (incremental peak (IP) = 0.59 +/- 0.13 nmol/l) but not in hypothyroid patients during therapy (IP = 0.19 +/- 0.02 nmol/l p < 0.02) or in the control group (IP = 0.15 +/- 0.04 nmol/l; p < 0.05). This study indicated that TRH administration is able to influence the sympathetic activity during hypothyroidism in humans.

Adult↗

PubMed1994

[Hyperprolactinemia in hypothyroidism: effects of L-thyroxine therapy].

It is well known that the pituitary PRL secretion is modified in patients with primary hypothyroidism. The serum PRL is elevated in approximately one third of patients, the others presenting with enhanced PRL release after TRH intravenous (i.v.) administration. The objective of this study was to verify how treatment with L-thyroxine modifies the enhanced PRL response to TRH administration in a group of patients with primary hypothyroidism. Eight female patients aged 28 to 64 (mean age +/- SD = 17.2 +/- 6.0) with primary hypothyroidism were studied. Diagnosis was based on clinical features and plasma FT4 (mean +/- SD = 5.2 +/- 0.9 pmol/l; n.r. 7.7-19.3 pmol/l) and TSH (mean +/- SD = 87.3 +/- 20 mUI/l; n.r. 0.2-5 mUI/l) levels. As controls eleven normal age-matched female subjects were also studied. After an overnight fasting an indwelling catheter was inserted into an antecubital vein of the forearm and kept patient by slow infusion of normal saline solution. After 60' the basal blood sample was collected and 200 mcg of TRH was injected intravenously (0'), further blood samples were taken at 30', 60', 90', 120' and 180'. PRL determinations (n.r. 3-19 ng/ml) of the blood samples obtained were made using fluoroimmunometric assay. Hypothyroid patients underwent a second TRH test after L-thyroxine replacement therapy (100 mcg/day) had led to euthyroidism for at least three months.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Indole-pyruvic acid, a tryptophan ketoanalogue, antagonizes the endocrine but not the behavioral effects of repeated stress in a model of depression.

Increased glucocorticoid secretion is frequent in mood disorders and is normalized by long-term antidepressant therapy. Many antidepressants act by increasing central serotonin transmission. We investigated the effects of a serotonin precursor, indole-pyruvic acid (IPA), in an animal model of depression based on repeated exposure to unpredictable stress. Rats were divided in groups, and IPA (20 mg/kg), the tricyclic antidepressant imipramine (IMI) (5 mg/kg), or vehicle was administered daily during 3 weeks of repeated exposure to various stressors according to the procedure described by Katz et al [Katz RJ, Roth KA, Carroll BJ (1981): Neurosci Biobehav Rev 5:247-251]. After treatment, rats were evaluated for stress-induced exploratory behavior and killed 24 hr later. Serum corticosterone levels and glucocorticoid receptor (GR) immunoreactivity (IR) in the nuclei of neurons located in the hippocampal subregion CA1 were also measured. Rats exposed to repeated stress showed a lower exploratory behavior score (p < 0.01), higher basal corticosterone levels (p < 0.01), and stronger GR IR in the hippocampus (p < 0.05) than control rats. All of these effects were antagonized by IMI treatment. IPA administration did not affect the behavioral response induced by repeated stress (p < 0.01) but normalized serum corticosterone levels. In addition, IPA treatment produced a decrease in GR IR (p < 0.05 versus control group) that was not modified by exposure to repeated stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗

PubMed1993

Centrally administered neuropeptide Y fails to increase food intake but enhances hypoalgesia in spontaneously hypertensive rats.

The effects of intracerebroventricular (i.c.v.) administration of neuropeptide Y (NPY1-36) on food intake and pain sensitivity in hot plate test were studied in spontaneously hypertensive rats (SHRs) and in normotensive Wistar-Kyoto (WKy) rats. In satiated SHRs NPY1-36 failed to significantly increase intake at doses that produced a strong effect in satiated WKy rats (0.25-1.25 nmol). Conversely, both NPY1-36 and the C-terminal fragment NPY13-36, a putative selective agonist for the Y2-receptor for NPY, enhanced the spontaneously occurring hypoalgesia of SHRs, having no effect in WKy rats. The present results indicate that the NPY central systems involved in the control of regulatory functions are differently tuned in SHRs and WKy rats, suggesting possible involvement of these systems in the genesis of hypertension.

Animals↗

PubMed1993

Involvement of alpha 2-receptors in the analgesia induced by transient forebrain ischemia in rats.

Transient forebrain ischemia induced in rats by the four-vessel occlusion method produced analgesic effects in the hotplate test that persisted for 2 weeks. Ischemia-induced analgesia was attenuated by low doses of alpha 2-agonist clonidine (0.01-0.10 mg/kg, IP) and enhanced by low doses of alpha 2-antagonists yohimbine (1-2 mg/kg, IP) and idazoxan (0.25-1.00 mg/kg, IP) administration 7 days after ischemia. Ischemia-induced analgesia was not affected by methysergide, naloxone, propranolol, or phenoxybenzamine administered 7 days after ischemia, when motor control and arousal level of rats recovered to normal conditions. The enhanced response to yohimbine was antagonized by pretreatment with clonidine (0.75 mg/kg, IP) and naloxone (10 mg/kg, IP), suggesting the involvement of endogenous opioid peptides. The enhanced response to yohimbine was still present 2 months after ischemia, when preischemic hotplate threshold was restored. As alpha 2-agonists reduce and alpha 2-antagonists increase the outflow of central noradrenaline, it is suggested that activation of central noradrenergic systems is involved in the mediation of ischemia-induced analgesia.

Adrenergic alpha-Antagonists↗