Alpha1-adrenergic antagonists act as 6-nitrodopamine receptor antagonists in the human vas deferens

doi:10.21203/rs.3.rs-3381934/v1

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Alpha1-adrenergic antagonists act as 6-nitrodopamine receptor antagonists in the human vas deferens

https://doi.org/10.21203/rs.3.rs-3381934/v1

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published 01 Nov, 2023

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Background: 6-Nitrodopamine (6-ND) is released from human vas deferens and plays a modulatory role in the male ejaculation. Therapeutical use of α₁-adrenoceptor antagonists is associated with ejaculatory abnormalities.

Objectives: To evaluate the effect of α₁-adrenoceptor antagonists on the contractions induced by 6-ND, dopamine, noradrenaline, and adrenaline in the human epididymal vas deferens (HEVD).

Methods: HEVD strips were suspended in glass chambers containing heated and oxygenated Krebs-Henseleit’s solution. Cumulative concentration-response curves to catecholamines (10 nM-300 mM) were constructed in HEVD strips pre-incubated (30 min) with doxazosin (0.1-1nM), tamsulosin (1-10 nM), prazosin (10-100 nM) and/or silodosin (0.1-10 nM). The effects of these α₁-adrenoceptor antagonists were also evaluated in the electric-field stimulation (EFS, 2-32 Hz)-induced contractions.

Results: Doxazosin (0.1 nM) caused significant reductions in 6-ND-induced HEVD contractions without affecting the contractions induced by dopamine, noradrenaline, and adrenaline. Similar results were observed with tamsulosin (1 nM) and prazosin (10 nM). At these concentrations, these α₁-adrenoceptor antagonists largely reduced the EFS-induced contractions. Silodosin (1 nM) caused concentration-dependent rightward shifts of the concentration-response curves to 6-ND but had no effect on the contractions induced by dopamine and adrenaline. Silodosin (0.1 nM) only inhibited the contractions induced by noradrenaline. Silodosin at 1 nM, but not at 0.1 nM, caused significant reductions in the EFS-induced contractions.

Discussion and conclusion: The results indicate that 6-ND plays a major role in the human vas deferens contractility and doxazosin, tamsulosin, prazosin and silodosin cause ejaculation disorders in man by blocking the 6-ND receptor rather than α₁-adrenoceptors.

Ejaculation

Delayed ejaculation

α-blockers

6-nitrodopamine (6-ND) is a novel catecholamine that is released from human umbilical cord vessels (Britto-Júnior et al., 2021a), human popliteal artery and vein (Oliveira et al., 2023) and human vas deferens (Britto-Júnior et al., 2022a), as detected by liquid chromatography coupled to tandem mass spectrometry. Although in human vascular tissues 6-ND acts mainly as a potent vasorelaxant, in human vas deferens 6-ND causes smooth muscle contraction, which is blocked by tricyclic antidepressants such as amitriptyline and desipramine, at concentrations that do not affect the spasmogenic actions of dopamine, noradrenaline, and adrenaline (Britto-Júnior et al., 2022a). Similar results have been observed in the rat epididymal vas deferens (Britto-Júnior et al., 2021b).

The α₁-adrenoceptor family is composed of three receptor subtypes, namely a_1A, α_1B and α_1D (Andersson et al., 2000). All three receptor subtypes are expressed in the human prostate, although in different locations (Walden et al., 1999). Blockade of α₁-adrenoceptors play an important role in the clinical management of patients with lower urinary tract symptoms (LUTS) caused by prostate hyperplasia (Roehrborn and Schwinn, 2004), and the α₁-adrenoceptor antagonists doxazosin, tamsulosin and silodosin are often used for LUTS relief (Debruyne, 2000). Although the treatment with α₁-adrenoceptor antagonists is generally well tolerated, one of the most frequent adverse reactions is abnormal ejaculation, as characterized by delayed ejaculation or absence of ejaculation during orgasm (Cho and Yoo, 2014). These adverse reactions could be due to inhibition of the emission phase of the ejaculation, in which the contraction of prostate, vas deferens, seminal vesicles and cauda epididymis occurs (Alwaal et al., 2015). Interestingly, α₁-adrenoceptor antagonists are now clinically used for the treatment of premature ejaculation (Gul et al., 2022).

In the rat isolated epididymal vas deferens, the contractions induced by 6-ND and by electric-field stimulation (EFS) are antagonized by pre-treatment of the vas deferens with doxazosin, tamsulosin, alfuzosin, terazosin and prazosin, at concentrations that do not block the contractions induced by dopamine, noradrenaline and adrenaline (Britto-Júnior et al., 2022c), indicating that these drugs could be acting as selective antagonists of 6-ND receptor rather than as α₁-adrenoceptor antagonists. Fluorescence histochemistry and biochemical detection of catecholamines revealed significant differences between rat and human vas deferens (Kaleczyc, 1998), i.e., the former receives numerous adrenergic nerve fibres (Owman & Sjöstrand, 1965), whereas the latter presents less dense adrenergic innervation (Alm, 1982; Baumgarten et al., 1968). Thus, we have investigated whether α₁-adrenoceptor antagonists would have inhibitory action on the contractions induced by 6-ND in human vas deferens.

Study participants

Participants who underwent vasectomy surgery in Centro Clínico NotreDame Intermedicas (Jundiaí, Sao Paulo) signed an informed consent approved by the Institute of Biomedical Sciences (ICB-USP) Institutional Review Board (Protocol number 4.468.508). The human epididymal vas deferens (HEVD) were obtained from 125 participants aged 28–59 years. The surgical procedure (Rogers & Kolettis, 2013) was performed under local anaesthesia and the excised segment (1.5 cm lenght) was taken at approximately 9 cm from the cauda epididymis.

HEVD functional assays

The HEVD strips (1.5 cm length) were suspended in a 10-mL glass chamber containing heated (37°C) and oxygenated (95%O₂: 5%CO₂) KHS. The isometric tension was kept at 10 mN and registered by a PowerLab system (ADInstruments, Dunedin, New Zealand‎). After a 45-min stabilization period, the HEVD strips were initially contracted with potassium chloride (KCl, 80 mM) to evaluate the tissue viability. After KCl removal and return to the baseline (15 min approximately), cumulative concentration-response curves to 6-ND (0.00001-1 mM) were constructed in control HEVD strips and in tissues pre-incubated with doxazosin (0.1, 0.3 and 1 nM, 30 min), tamsulosin (0.1, 1 and 10 nM, 30 min), prazosin (10, 30 and 100 nM, 30 min) and/or silodosin (0.1, 1, 3 and 10 nM, 30 min). Cumulative concentration-response curves to noradrenaline were constructed in HEVD pre-incubated or not with doxazosin (0.1 nM, 30 min), tamsulosin (1 nM, 30 min), prazosin (10 nM, 30 min) and/or silodosin (0.1 and 10 nM, 30 min). Cumulative concentration-response dopamine and adrenaline were constructed in HEVD pre-incubated or not with doxazosin (0.1 nM, 30 min), tamsulosin (1 nM, 30 min), prazosin (10 nM, 30 min) and/or silodosin (1 nM, 30 min).

Electric-field stimulation (EFS) in HEVD preparations

The HEVD strips were submitted to EFS (60 V for 20 sec, at 2–32 Hz in square-wave pulses, 0.3 ms pulse width, and 0.1 ms delay), using a Grass S88 stimulator (Astro-Medical, Industrial Park, RI, USA). The EFS-induced HEVD contractions were conducted in control and tissues pre-incubated with doxazosin (0.1 nM, 30 min), tamsulosin (1 nM, 30 min), prazosin (10 nM, 30 min) and/or silodosin (0.1 and 1 nM, 30 min).

Materials and drugs

Dopamine and prazosin were obtained from Sigma-Aldrich Chemicals Co. (St Louis, Missouri, USA). Adrenaline, noradrenaline and silodosin were purchased from Cayman Chemical Co (Michigan, USA). 6-Nitrodopamine was acquired from Toronto Research Chemicals (Ontario, CA). Tamsulosin was obtained from Swati Spentose Pvt Ltd (Vapi, Gujarat, India). Doxazosin was obtained from Nifty Labs Pvt Ltd (Hyderabad, Telangana, India). Sodium chloride (NaCl), potassium chloride (KCl), calcium chloride (CaCl₂), magnesium sulfate (MgSO₄), sodium bicarbonate (NaHCO₃), potassium phosphate monobasic (KH₂PO₄) and glucose were acquired from Merck KGaA (Darmstadt, Germany).

Data Analysis

The values of pEC₅₀ and Emax data represent the mean ± standard error of the mean (S.E.M.) of n experiments. Values of E_max were expressed in mN. One was used as the control response and the other HEVD was incubated with an antagonist / inhibitor.

The pA₂ values of the antagonists were calculated from application of the equation; pA₂ = log (antagonist concentration) − log (CR-1) -log (antagonist concentration). The methods for determining both pEC50 and Emax, and the statistical tests employed, were described elsewhere (Britto-Júnior et al., 2022a).

Effect of doxazosin

Cumulative addition of 6-ND (10^− 8 to 10^− 3 M; Fig. 1A), dopamine (10^− 8 to 10^− 3 M; Fig. 1B), noradrenaline (10^− 8 to 3×10^− 4 M; Fig. 1C) and adrenaline (10^− 8 to 3×10^− 4 M; Fig. 1D) produced concentration-dependent contractions in the HEVD strips (Fig. 1A). The in vitro pre-treatment (30 min) of the HEVD with doxazosin (0.1-1 nM) significantly reduced the Emax values to 6-ND with a pA₂ value of 10.38 ± 0.20 (n = 6). However, doxazosin (0.1 nM) did not affect Emax and pEC₅₀ the HEVD contractions induced by dopamine (Fig. 1B), noradrenaline (Fig. 1C) and adrenaline (Fig. 1D). The pEC₅₀ and Emax data for 6-ND, dopamine, noradrenaline and adrenaline in control and doxazosin-treated preparations are shown in Table 1.

Table 1

The effect of doxazosin on the potency (pEC₅₀) and maximal responses (E_max) of the contractions induced by 6-nitrodopamine (6-ND), noradrenaline (NA), adrenaline (ADR), and dopamine (DA) in the human isolated epididymal vas deferens.
Catecholamine	pEC₅₀ (log[M])	E_max (mN)	n
6-ND	4.10 ± 0.15	57.08 ± 8.49	6
+ doxazosin 0.1 nM	3.71 ± 0.19*	44.66 ± 10.98	6
+ doxazosin 0.3 nM	3.54 ± 0.22*	35.66 ± 7.87*	6
+ doxazosin 1 nM	4.20 ± 0.31	20.01 ± 8.10*	4
DA	3.99 ± 0.30	33.53 ± 12.01	6
+ doxazosin 1 nM	4.01 ± 0.30	41.77 ± 13.98	6
NA	4.19 ± 0.14	31.9 ± 11.8	4
+ doxazosin 1 nM	4.04 ± 0.31	26.7 ± 5.1	4
ADR	4.85 ± 0.19	35.4 ± 17.1	4
+ doxazosin 1 nM	5.06 ± 0.52	33.6 ± 25.8	4
pEC50 is defined as the negative logarithm of the EC₅₀. Emax is the maximal effect at the highest drug concentration. The pEC₅₀and Emax were expressed as mean ± SEM (n means the number of vas deferens strips). P < 0.05 compared with respective control values.*

Electrical-field stimulation (EFS; 2–32 Hz) evoked frequency-dependent contractile responses in the HEVD strips (Fig. 1E), which were significantly reduced by doxazosin (0.1 nM) in all frequencies tested (p = 0.0001; n = 6; Fig. 1E).

Effect of tamsulosin

Pre-treatment (30 min) of the HEVD with tamsulosin (1 and 10 nM) caused significant rightward shifts on the concentration-response curves to 6-ND (Fig. 2A) with a pA₂ value of 9.63 ± 0.06 (n = 5). At 10 nM, tamsulosin nearly abolished the 6-ND-induced contractions (Fig. 2A). Tamsulosin (1 nM) did not affect the HEVD contractions induced by dopamine (Fig. 2B), noradrenaline (Fig. 2C) and adrenaline (Fig. 2D). The pEC₅₀ and Emax data for 6-ND, dopamine, noradrenaline and adrenaline in control and tamsulosin-treated preparations are shown in Table 2.

Table 2

The effect of tamsulosin on the potency (pEC₅₀) and maximal responses (E_max) of the contractions induced by 6-nitrodopamine (6-ND), noradrenaline (NA), adrenaline (ADR), and dopamine (DA) in the human isolated epididymal vas deferens.
Catecholamine	pEC₅₀ (log[M])	E_max (mN)	n
6-ND	4.01 ± 0.12	41.93 ± 4.52	8
+ tamsulosin 0.1 nM	4.00 ± 0.10	45.75 ± 6.63	4
+ tamsulosin 1 nM	3.45 ± 0.07*	37.36 ± 11.47	5
+ tamsulosin 10 nM		11.58 ± 7.01*	4
DA	4.59 ± 0.22	30.23 ± 0.91	3
+ tamsulosin 1 nM	4.03 ± 0.10	37.54 ± 5.06	3
NA	4.37 ± 0.11	40.32 ± 9.45	6
+ tamsulosin 1 nM	4.38 ± 0.08	42.01 ± 5.21	6
ADR	5.03 ± 0.18	37.15 ± 19.33	3
+ tamsulosin 1 nM	4.86 ± 0.24	35.93 ± 16.99	3
pEC50 is defined as the negative logarithm of the EC₅₀. Emax is the maximal effect at the highest drug concentration. The pEC50 and Emax were expressed as mean ± SEM (n means the number of vas deferens strips). P < 0.05 compared with respective control values.*

Tamsulosin (1 nM) caused marked reductions (p = 0.0002) in the HEVD contractions induced by EFS (2–32 Hz; Fig. 2E).

Effect of prazosin

Pre-treatment (30 min) of the HEVD with prazosin (10–100 nM) caused significant rightward shifts on the concentration-response curves to 6-ND (Fig. 3A) with a pA₂ value of 8.23 ± 0.52 (n = 6). At 100 nM, prazosin markedly reduced the maximal responses to 6-ND (Fig. 3A). Prazosin (10 nM) did not affect the HEVD contractions induced by dopamine (Fig. 3B), noradrenaline (Fig. 3C) and adrenaline (Fig. 3D). The pEC₅₀ and Emax data for 6-ND, dopamine, noradrenaline and adrenaline in control and prazosin-treated preparations are shown in Table 3.

Table 3

The effect of prazosin on the potency (pEC₅₀) and maximal responses (E_max) of the contractions induced by of 6-nitrodopamine (6-ND), noradrenaline (NA), adrenaline (ADR), and dopamine (DA) in the human isolated epididymal vas deferens.
Catecholamine	pEC₅₀ (log[M])	E_max (mN)	n
6-ND	4.62 ± 0.11	62.55 ± 8.31	6
+ prazosin 10 nM	4.08 ± 0.25*	49.64 ± 6.67	6
+ prazosin 30 nM	3.47 ± 0.30*	58.42 ± 13.26	4
+ prazosin 100 nM	3.12 ± 1.24*	27.89 ± 11.66*	4
DA	4.62 ± 0.05	33.42 ± 9.26	4
+ prazosin 10 nM	4.55 ± 0.10	31.39 ± 9.44	4
NA	4.73 ± 0.34	32.25 ± 4.9	4
+ prazosin 10 nM	4.68 ± 0.22	34.79 ± 7.55	4
ADR	5.14 ± 0.29	57.76 ± 11.25	3
+ prazosin 10 nM	5.19 ± 0.33	54.14±14.53	3
pEC50 is defined as the negative logarithm of the EC₅₀. Emax is the maximal effect at the highest drug concentration. The pEC₅₀and Emax were expressed as mean ± SEM. n means the number of vas deferens strips. P < 0.05 compared with respective control values.*

Prazosin (10 nM) caused significant reductions (p = 0.0042) in the HEVD contractions induced by EFS (2–32 Hz; Fig. 3E).

Effect of silodosin

Pre-treatment of the HVED with silodosin (1–10 nM) caused significant rightward shifts on the concentration-response curves to 6-ND (Fig. 4A) with a pA₂ value of 9.84 ± 0.06 (n = 3). At 10 nM, silodosin almost abolished the contractions induced by 6-ND (Fig. 4A). Silodosin (1 nM) did not affect the HEVD contractions induced by dopamine (Fig. 4B) and adrenaline (Fig. 4D). Silodosin (0.1 and 1 nM) caused significant rightward shifts on the concentration-response curves to noradrenaline (Fig. 4C) with a pA₂ value of 10.71 ± 0.12 (n = 6). The pEC₅₀ and Emax data for 6-ND, dopamine, noradrenaline and adrenaline in control and silodosin-treated preparations are shown in Table 4.

Table 4

The effect of silodosin on the potency (pEC₅₀) and the maximum response (E_max) of the contractions induced by of 6-nitrodopamine (6-ND), noradrenaline (NA), adrenaline (ADR), and dopamine (DA), in the human isolated epididymal vas deferens.
Catecholamine	pEC₅₀ (log[M])	E_max (mN)	n
6-ND	3.93 ± 0.16	45.43 ± 7.38	7
+ silodosin 0.1 nM	4.15 ± 0.12	40.81 ± 17.69	3
+ silodosin 1 nM	3.19 ± 0.13*	21.57 ± 5.94*	3
+ silodosin 3 nM	-	27.53 ± 7.26*	4
+ silodosin 10 nM	-	6.02 ± 1.18*	4
DA	4.35 ± 0.23	28.71 ± 8.33	4
+ silodosin 1 nM	4.09 ± 0.32	25.50 ± 6.44	4
NA	5.04 ± 0.17	49.37 ± 8.6	10
+ silodosin 0.1 nM	4.51 ± 0.22*	38.82 ± 12.96	4
+ silodosin 1 nM	3.56 ± 0.35*	36.56 ± 6.33	6
ADR	4.92 ± 0.15	38.68 ± 8.83	6
+ silodosin 1 nM	4.63 ± 0.25	46.98 ± 14.90	6
pEC50 is defined as the negative logarithm of the EC₅₀. Emax is the maximal effect at the highest drug concentration. The pEC50, Emax and the mean shifts were expressed as mean ± SEM (n means the number of vas deferens strips). P < 0.05 compared with respective control values.*

Silodosin (0.1 nM) did not affect the EFS-induced HEVD contractions (Fig. 4E). However, at 1 nM, silodosin caused significant reductions in the HEVD contractions induced by EFS (Fig. 4F).

Incidence of abnormal ejaculation is a typical adverse reaction of α₁-adrenoceptor antagonists (Michel, 2007). This class of drugs induces relaxations of prostate, urethra and bladder neck smooth muscle (Andersson, 2000), reducing the resistance of the prostatic urethra and bladder neck to the ejaculate coming from the vas deferens, thus allowing retrograde ejaculation to occur (van Dijk et al., 2006). However, in healthy volunteers treated for 5 days with either tamsulosin or alfuzosin, few individuals (95%) had increased post-ejaculate in the urine, indicating that α₁-adrenoceptor antagonists may cause anejaculation rather than retrograde ejaculation (Hellstrom et al., 2005); Thus, evaluation of the effect of these compounds in human vas deferens and seminal vesicles may provide useful information on the mechanism(s) involved.

Silodosin (KMD-3213; Shibata et al., 1995) has an increased affinity to adrenoceptor α_1A (0.039 nM) compared to α_1B (6.5 nM) and α_1D (2.2 nM; Tatemichi et al., 2006) in the lower urinary tract. In comparison to the α₁-adrenoceptor antagonists alfuzosin (Ramsay et al., 1988), doxazosin (Elliott et al., 1982; Wilt and MacDonald, 2006), tamsulosin (Lepor et al., 1988; Dunn et al., 2002), terazosin (Frishman et al., 1988; O'Leary 2001), and prazosin (U'Prichard et al., 1978), silodosin was the most potent antagonist on the contractions induced by noradrenaline in the rat epididymal vas deferens (Britto-Júnior et al., 2022c). As shown here, silodosin was also more potent than tamsulosin, doxazosin and prazosin to inhibit noradrenaline-induced HEVD contractions. Interestingly, silodosin was the only α₁-adrenoceptor antagonist that was more potent to inhibit HEVD contractions induced by noradrenaline, as compared to those induced by 6-ND. Since tamsulosin and silodosin are the α₁-adrenoceptor antagonists more associated with abnormal ejaculation (Cui et al., 2012), selectivity for the α_1A-adrenoceptor subtype could be the mechanism involved in this adverse reaction. Indeed, incidence of abnormal ejaculation in patients treated with prazosin is rare, and in the rat isolated vas deferens, prazosin presents low potency on α_1A- and high potency at α_1D-adrenoceptor (Docherty, 2013).

6-Nitrodopamine concentration-dependently contract both rat (Britto-Júnior et al., 2021b) and human (Britto-Júnior et al., 2022a) vas deferens, but more importantly, potentiates the contractile action of the dopamine, noradrenaline, and adrenaline in rat epididymal vas deferens at a very low concentration such as 10 pM (Britto-Júnior et al., 2023a). Although this mechanism is not clear, the potentiation is abolished when the vas deferens is pre-treated with the voltage-gated sodium channel blocker tetrodotoxin, suggesting that may be due to activation of adrenergic terminals (Britto-Júnior et al., 2023a). A similar potentiation of 6-ND on the increased atrial frequency induced by dopamine, noradrenaline and adrenaline was observed in the rat isolated atria (Britto-Júnior et al., 2023b). The blockade of α_1A adrenoceptors in the rat vas deferens could lead to infertility (Michel et al., 2007); however, in α₁-adrenoceptor subtype-selective knockout mice (α_1A-, α_1B- and α_1D-adrenoceptor knockout), the contractions of the vas deferens induced by electric-field stimulation was reduced by 60–70%, but not abolished (Sanbe et al., 2007), indicating the presence of another receptor responsible for the observed contractions. This receptor could be the 6-ND receptor. Our finding that silodosin, at a concentration (100 pM) that caused marked reductions in noradrenaline-induced contractions, did not affect the contractions induced by EFS, reinforces the concept that 6-ND is a major modulator of human vas deferens contractility (Britto-Júnior et al., 2022a). Indeed, inhibition of the EFS-induced HEVD contractions was only observed when the α₁-adrenoceptor antagonists were used at concentrations that inhibited those induced by 6-ND.

Inconsistencies in the interactions of α₁-adrenoceptor antagonists and ejaculatory function have been observed in mouse, rat and human data (Michel, 2007), and as summarized in Table 5, they are also present in the pharmacology of 6-ND in rat and human vas deferens. The remarkable synergism between 6-ND and the classical catecholamines (dopamine, noradrenaline, and adrenaline) has been described so far only on the rat epididymal vas deferens (Britto-Júnior et al., 2023a) and rat isolated right atrium (Britto-Júnior et al., 2023b). Thus, it would be important to confirm the synergism in HEVD. Furthermore, purification and sequence of the 6-ND receptor from human vas deferens should help to deep our understanding on the physiological processes involved in the ejaculation.

Table 5

6-ND pharmacology in rat and human vas deferens
	Rat	Ref	Human	Ref
6-ND release (ng/mL)	1.4±0.4	Britto-Júnior et al., 2021b	1.9±0.8	Britto-Júnior et al., 2022a
Noradrenaline (ng/mL)	0.4±0.2	Britto-Júnior et al., 2021b	0.5±0.2	Britto-Júnior et al., 2022a
Dopamine release (ng/mL)	-	Britto-Júnior et al., 2021b	0.3±0.1	Britto-Júnior et al., 2022a
Adrenaline release (ng/mL)	-	Britto-Júnior et al., 2021b	0.2±0.1	Britto-Júnior et al., 2022a
6-ND contractile (pEC₅₀)	5.2±0.2	Britto-Júnior et al., 2023a	4.6±0.1	this manuscript
Abolished by TTX	+	Lima et al., 2022	?
L-NAME on 6-ND release	↓	Britto-Júnior et al., 2021b	↓	Britto-Júnior et al., 2022a
L-NAME on EFS contraction	-	Britto-Júnior et al., 2021b	↓	Britto-Júnior et al., 2022a
b₁ and b_1/b₂ antagonists	+	Lima et al., 2022	?
Potentiates DA, NA and ADR	+	Britto-Júnior et al., 2023a	?
Tricyclic compounds (pA₂):
Amitriptyline	7.7±0.5	Britto-Júnior et al., 2021b	8.9±0.1	Britto-Júnior et al., 2022a
Desipramine	8.2±0.1	Britto-Júnior et al., 2021b	9.5±0.1	Britto-Júnior et al., 2022a
Carbamazepine	7.7±0.4	Britto-Júnior et al., 2021b	8.8±0.1	Britto-Júnior et al., 2022a
α₁ antagonists (pA₂):
Doxazosin	9.1±0.1	Britto-Júnior et al., 2021c	10.3±0.2	this manuscript
Tamsulosin	9.7±0.1	Britto-Júnior et al., 2021c	9.3±0.1	this manuscript
Silodosin	8.8±0.1	Britto-Júnior et al., 2021c	9.8±0.1	this manuscript
Prazosin	7.7±0.2	Britto-Júnior et al., 2021c	8.2±0.5	this manuscript

The α₁-adrenoceptor antagonists doxazosin, tamsulosin, prazosin and silodosin only block the contractions of human isolated vas deferens at concentrations that inhibit 6-ND induced contractions reinforcing the concept that this novel catecholamine acts as a major modulator of human vas deferens contractility.

Ethical Approval

The investigation followed the principles outlined in the Declaration of Helsinki and the protocol was approved by the Ethics Committee of the Institute of Biomedical Sciences of the University of São Paulo – ICB/USP (protocol number 4.468.508), and the patients were asked to sign an informed consent.

Consent to Participate

Not applicable.

Consent to Publish

The authors authorize the submission and publication of this article in Naunyn-Schmiedeberg's Archives of Pharmacology

Author Contributions Statement

Conceptualization: JBJ, GDN.

Data curation: JBJ, GDN.

Formal analysis: GDN

Funding acquisition: EA, GDN.

Investigation: RABG, JBJ, ATL, DLO, GQJ, GAOS.

Methodology: RABG, ATL.

Project administration: GDN.

Supervision: EA and GDN.

Visualization: AF, EA, GDN.

Writing – original draft: JBJ, GDN

The authors declare that all data were generated in-house and that no paper mill was used.

Funding:

Sao Paulo Research Foundation (FAPESP) grants 2021/14414-8 (JBJ), 2017/15175-1 (EA); 2019/16805-4 (GDN).

National Council for Scientific and Technological Development (CNPq) grant 303839/2019-8 (GDN)

Competing interests: Authors declare that they have no competing interests.

Availability of data and materials

The authors authorize the availability of any data used in this study.

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Alpha1-adrenergic antagonists act as 6-nitrodopamine receptor antagonists in the human vas deferens

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Abstract

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INTRODUCTION

MATERIALS AND METHODS

Study participants

HEVD functional assays

Electric-field stimulation (EFS) in HEVD preparations

Materials and drugs

Data Analysis

RESULTS

Effect of doxazosin

Effect of tamsulosin

Effect of prazosin

Effect of silodosin

DISCUSSION

CONCLUSION

Declarations

References

Additional Declarations

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Journal Publication

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