Puberty installation and adrenergic response of seminal vesicle from rats exposed prenatally to hydrocortisone

We investigated the effects of hydrocortisone during the prenatal period and its repercussion on puberty installation and adrenergic response of seminal vesicle in adult rats. The efficacy of the hydrocortisone treatment in reducing adrenal wet weight immediately after delivery in both the treated mothers and respective pups at birth may indicate impairment of the hypothalamus-pituitary-adrenal axis. This parameter was unchanged in the adult phase of these descendants, suggesting recuperation of this axis. In addition, the treatment with hydrocortisone delayed the age of puberty installation, probably by absence of both physiologic production and liberation of luteinizing hormone and testosterone. Despite the significant reduction in testosterone level as well as of wet weights of both vas deferens and testis in the adult phase, no difference was observed in the sensitivity of the seminal vesicle to the studied sympathetic agonist. However, the observed reduction in contractile response of the seminal vesicle may be a consequence of contractile-system damage in this organ. It is possible that this alteration may cause a reduction in the amount of vesicular secretion so important in the process of ejaculation. In conclusion, these results suggest that administration of hydrocortisone in late prenatal life did not influence the hypothalamus-pituitary-adrenal axis in adult life, although it altered the hypothalamus-pituitary-gonadal axis, and reduced testosterone production starting at puberty, as a consequence of an incomplete masculinization of the hypothalamus plus a reduction in the contractile response of the seminal vesicle. (c) 2005 Elsevier B.V. All rights reserved.

Adrenergic response patterns in vas deferens isolated from rats under diurnal rhythms - Influence of stress

The aim of this study was to verify, by means of functional methods, whether the circadian rhythm changes adrenergic response patterns in the epididymal half of the vas deferens isolated from control rats as well as from rats submitted to acute stress. The experiments were performed at 9:00 a.m., 3:00 p.m., 9:00 p.m., and 3:00 a.m. The results showed a light-dark dependent variation of the adrenergic response pattern on organs isolated from control as well as from stressed rats. In the control group, only the phenylephrine sensitivity was changed throughout the circadian rhythm. Under the stress condition, both norepinephrine and phenylephrine response patterns were changed, mainly during darkness. The maximal contractile response to both alpha- and beta-agonist and alpha(1)-agonist was increased in the dark phase, corresponding to high plasmatic concentrations of endogenous melatonin. The vas deferens isolated from stressed rats during the light phase simultaneously incubated with exogenous melatonin showed the same pattern of response obtained in the dark phase, thus indicating a peripheric action of melatonin on this organ. Therefore, the circadian rhythms are important to the adrenergic response pattern in rat vas deferens from both control and stressed rats. In conclusion, we suggest a melatonin modulation on alpha(1)-postsynaptic adrenergic response in the rat vas deferens. (c) 2005 Elsevier B.V. All rights reserved.

ROLE OF CHOLINERGIC AND ADRENERGIC PATHWAYS OF THE MEDIAL SEPTAL AREA IN THE WATER-INTAKE AND PRESSOR-RESPONSE TO CENTRAL ANGIOTENSIN-II AND CARBACHOL IN RATS

In the present study, we investigated the effect of previous injection of either prazosin (alpha 1-adrenergic antagonist) or atropine (muscarinic cholinergic antagonist) into the medial septal area (MSA) on the presser and dipsogenic responses induced by intracerebroventricular (ICV) injection of carbachol (cholinergic agonist) and angiotensin II (ANGII) in rats. The presser and dipsogenic responses to ICV carbachol (7 nmol) were reduced after previous treatment of the MSA with atropine (0.5 to 5 nmol), but not prazosin (20 and 40 nmol). The dipsogenic response to ICV ANGII (25 ng) was reduced after prazosin (40 nmol) into the MSA. The presser response to ICV ANGII was not changed either by previous treatment of the MSA with prazosin or atropine. The present results suggest a dissociation among the pathways subserving the control of dipsogenic and presser responses to central cholinergic or angiotensinergic activation.

Chronotropic response of beta-adrenergic-, muscarinic-, and calcitonin gene-related peptide-receptor agonists in right atria from neonatal capsaicin-treated rats

We evaluated the potency of isoproterenol, carbachol, pilocarpine and calcitonin gene-related peptide (CGRP) in the rat right atria at 30, 60 and 90 days after neonatal capsaicin treatment. Neonatal rats were pretreated on the second day of life with capsaicin (50 mg/kg). The capsaicin pretreatment caused a five-fold rightward shift at the pEC(50) level on the concentration-response curves to isoproterenol in 30-day-old rats. Propranolol (10 mg/kg, given 15 min prior to capsaicin treatment) prevented this subsensitivity. No changes in the potency of isoproterenol were observed at 60 and 90 days after capsaicin pretreatment. The potency and maximal responses of CGRP in the right atria in 30-day-old rats were significantly higher than in 60- and 90-day-old rats; however, no differences were found between control and capsaicin groups. The potency and maximal responses to carbachol and pilocarpine were not changed in all groups. The neonatal capsaicin treatment reduced by about 74% the CGRP content in the heart in all groups. In summary, capsaicin treatment in newborn rats produces a desensitization of chronotropic response mediated by beta-adrenoceptors in isolated right atria from 30-day-old rats possibly due to a massive release of catecholamines. (C) 2002 Elsevier B.V. Ireland Ltd. All rights reserved.

Central serotonergic and adrenergic/imidazoline inhibitory mechanisms on sodium and water intake

Recent studies have shown the existence of two important inhibitory mechanisms for the control of NaCl and water intake: one mechanism involves serotonin in the lateral parabrachial nucleus (LPBN) and the other depends on alpha(2)-adrenergic/imidazoline receptors probably in the forebrain areas. In the present study we investigated if alpha(2)-adrenergic/imidazoline and serotonergic inhibitory mechanisms interact to control NaCl and water intake. Male Holtzman rats with cannulas implanted simultaneously into the lateral ventricle (LV) and bilaterally into the LPBN were used. The ingestion of 0.3 M NaCl and water was induced by treatment with the diuretic furosemide (10 mg/kg of body weight)+the angiotensin converting enzyme inhibitor captopril (5 mg/kg) injected subcutaneously 1 h before the access of rats to water and 0.3 M NaCl. Intracerebroventricular (i.c.v.) injection of the alpha(1)-adrenergic/imidazoline agonist clonidine (20 nmol/l RI) almost abolished water (1.6 +/- 1.2, vs. vehicle: 7.5 +/- 2.2 ml/2 h) and 0.3 M NaCl intake (0.5 +/- 0.3, vs. vehicle: 2.2 0.8 ml/2 h). Similar effects were produced by bilateral injections of the 5HT(2a/2b) serotonergic agonist 2,5-dimetoxy-4-iodoamphetamine (DOI, 5 mug/0.2 mul each site) into the LPBN on water (3.6 +/- 0.9 ml/2 h) and 0.3 M NaCl intake (0.4 +/- 0.2 m1/2 h). Injection of the (alpha(2)-adrenergic/imidazoline antagonist idazoxan (320 nmol) i.c.v. completely blocked the effects of clonidine on water (8.4 +/- 1.5 ml/2 h) and NaCl intake (4.0 +/- 1.2 ml/2 h), but did not change the effects of LPBN injections of DOI on water (4.2 +/- 1.0 ml/2 h) and NaCl intake (0.7 +/- 0.2 ml/2 h). Bilateral injections of methysergide (4 mug/0.2 mul each site) into the LPBN increased 0.3 M NaCl intake (6.4 +/- 1.9 ml/2 h), not water intake. The inhibitory effect of i.c.v. clonidine on water and 0.3 M NaCl was still present after injections of methysergide into the LPBN (1.5 +/- 0.8 and 1.7 +/- 1.4 ml/2 h, respectively). The results show that the inhibitory effects of the activation of a,-adrenergic/imidazoline receptors in the forebrain are still present after blockade of the LPBN serotonergic mechanisms and vice versa for the activation of serotonergic mechanisms of the LPBN. Therefore, each system may act independently to inhibit NaCl and water intake. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Effects of central alpha-adrenergic agonists on hormone-induced 3% NaCl and water intake

Male rats received intracerebroventricular (ICV) renin (600 ng) or daily subcutaneous injections of deoxycorticosterone (5 mg) to induce 3% NaCl and water intake. Noradrenaline (NOR; 40-160 nmol) and clonidine (CLO; 5-20 nmol) injected ICV. induced 70 to 100% inhibition of the intakes. Phenylephrine (PHE; 40-160 nmol) injected ICV induced 60 to 95% inhibition of the intakes. NOR and PHE induced a stronger inhibition on the 3% NaCl intake induced by renin than on the intake induced by deoxycorticosterone (DOC), and CLO did the opposite. CLO was always more effective than PHE to induce inhibition of the intakes. The results suggest that NOR inhibits hormone (angiotensin II, aldosterone)-induced NaCl intake by acting mainly on alpha(2)-adrenergic receptors.

Differential distribution of functional alpha(1)-adrenergic receptor subtypes along the rat tail artery

The rat tail artery has been used for the study of vasoconstriction mediated by alpha(1A)-adrenoceptors (ARs). However, rings from proximal segments of the tail artery (within the initial 4 cm, PRTA) were at least 3- fold more sensitive to methoxamine and phenylephrine (n = 6 - 12; p < 0.05) than rings from distal parts (between the sixth and 10th cm, DRTA). Interestingly, the imidazolines N-[ 5-( 4,5- dihydro- 1H- imidazol-2-yl)-2-hydroxy-5,6,7,8- tetrahydronaphthalen- 1- yl] methanesulfonamide hydrobromide (A-61603) and oxymetazoline, which activate selectively alpha(1A)- ARs, were equipotent in PRTA and DRTA (n = 4 - 12), whereas buspirone, which activates selectively alpha(1D)-AR, was approximate to 70-fold more potent in PRTA than in DRTA (n = 8; p < 0.05). The selective alpha(1D)-AR antagonist 8-[2-[4-(methoxyphenyl)-1-piperazinyl] ethyl]-8-azaspiro[4.5] decane-7,9-dione dihydrochloride (BMY- 7378) was approximate to 70- fold more potent against the contractions induced by phenylephrine in PRTA (pK(B) of approximate to 8.45; n = 6) than in DRTA (pK B of approximate to 6.58; n = 6), although the antagonism was complex in PRTA. 5-Methylurapidil, a selective alpha(1A)-antagonist, was equipotent in PRTA and DRTA (pK(B) of approximate to 8.4), but the Schild slope in DRTA was 0.73 +/- 0.05 ( n = 5). The noncompetitive alpha(1B)-antagonist conotoxin rho-TIA reduced the maximal contraction induced by phenylephrine in DRTA, but not in PRTA. These results indicate a predominant role for alpha(1A)-ARs in the contractions of both PRTA and DRTA but with significant coparticipations of alpha(1D)-ARs in PRTA and alpha(1B)-ARs in DRTA. Semiquantitative reverse transcription-polymerase chain reaction revealed that mRNA encoding alpha(1A)- and alpha(1B)-ARs are similarly distributed in PRTA and DRTA, whereas mRNA for alpha(1D)-ARs is twice more abundant in PRTA. Therefore, alpha(1)-ARs subtypes are differentially distributed along the tail artery. It is important to consider the segment from which the tissue preparation is taken to avoid misinterpretations on receptor mechanisms and drug selectivities. antagonism was complex in PRTA. 5- Methylurapidil, a selective alpha(1A)-antagonist, was equipotent in PRTA and DRTA (pK(B) of approximate to 8.4), but the Schild slope in DRTA was 0.73 +/- 0.05 ( n = 5). The noncompetitive alpha(1B)-antagonist conotoxin rho-TIA reduced the maximal contraction induced by phenylephrine in DRTA, but not in PRTA. These results indicate a predominant role for alpha(1A)-ARs in the contractions of both PRTA and DRTA but with significant coparticipations of alpha(1D)-ARs in PRTA and alpha(1B)-ARs in DRTA. Semiquantitative reverse transcription-polymerase chain reaction revealed that mRNA encoding alpha(1A)- and alpha(1B)- ARs are similarly distributed in PRTA and DRTA, whereas mRNA for alpha(1D)-ARs is twice more abundant in PRTA. Therefore, alpha(1)-ARs subtypes are differentially distributed along the tail artery. It is important to consider the segment from which the tissue preparation is taken to avoid misinterpretations on receptor mechanisms and drug selectivities.

The N terminus of the human alpha(1D)-adrenergic receptor prevents cell surface expression

We previously reported that truncation of the N-terminal 79 amino acids of alpha(1D)-adrenoceptors (Delta(1-79)alpha(1D)-ARs) greatly increases binding site density. In this study, we determined whether this effect was associated with changes in alpha(1D)-AR subcellular localization. Confocal imaging of green fluorescent protein (GFP)-tagged receptors and sucrose density gradient fractionation suggested that full-length alpha(1D)-ARs were found primarily in intracellular compartments, whereas Delta(1-79)alpha(1D)-ARs were translocated to the plasma membrane. This resulted in a 3- to 4-fold increase in intrinsic activity for stimulation of inositol phosphate formation by norepinephrine. We determined whether this effect was transplantable by creating N-terminal chimeras of alpha(1)-ARs containing the body of one subtype and the N terminus of another (alpha(1A) NT-D, alpha(1B) NT-D, alpha(1D) NT-A, and alpha(1D)NT-B). When expressed in human embryonic kidney 293 cells, radioligand binding revealed that binding densities of alpha(1A)- or alpha(1B)-ARs containing the alpha(1D)-N terminus decreased by 86 to 93%, whereas substitution of alpha(1A)- or alpha(1B)-N termini increased alpha(1D)-AR binding site density by 2- to 3-fold. Confocal microscopy showed that GFP-tagged alpha(1D)NT-B-ARs were found only on the cell surface, whereas GFP-tagged alpha(1B)NT-D-ARs were completely intracellular. Radioligand binding and confocal imaging of GFP-tagged alpha(1D)- and Delta(1-79)alpha(1D)-ARs expressed in rat aortic smooth muscle cells produced similar results, suggesting these effects are generalizable to cell types that endogenously express alpha(1D)-ARs. These findings demonstrate that the N-terminal region of alpha(1D)-ARs contain a transplantable signal that is critical for regulating formation of functional bindings, through regulating cellular localization.

Central alpha-adrenergic agonists and need-induced 3% NaCl and water intake

In the present study, noradrenaline (NOR, alpha-non-specific adrenergic agonist), clonidine (CLO, alpha(2)), phenylephrine (PHE, alpha(1)) or isoproterenol (ISO, beta-agonist) was injected in the medial septal area (MSA) of water-deprived, sodium-deplete or food-deprived rats. NOR (80, 160 nmol) inhibited the intake of 3% NaCl, water deprivation-induced and meal-associated water intake. Food deprivation-induced food intake and 10% sucrose intake were not altered by NOR. CLO (10, 20, 30, 40 nmol) inhibited (80-100% inhibition compared to control during 60 min) the intake of 3% NaCl, water deprivation-induced and meal-associated water intake. CLO had a weaker inhibition on food and 10% sucrose intake (30-50% less than the control during 60 and 15 min, respectively). PHE (160 nmol) inhibited 3% NaCl intake and 10% sucrose intake (30% less than the control for 15-30 min). ISO (160 nmol) did not after water or 3% NaCl intake. NOR induced an increase, CLO and ISO induced a decrease, and PHE no alteration in mean arterial pressure. NOR did not alter water or 3% NaCl intake when injected unilaterally into the caudate nucleus. The results suggest that NOR injected in the MSA acts on alpha(2)-adrenergic receptors inducing a specific inhibition of 3% NaCl and water intake. (C) 1997 Elsevier B.V.