Evidence for the presence of β2-inhibitory adrenoceptors in the rat vas deferens

Vohra, M. M.

doi:10.1016/0306-3623(79)90093-4

Cited by 19 publications

(10 citation statements)

References 4 publications

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“…This agrees with previous findings using this prep-aration (Ganguly & Bhattacharya, 1969;Vohra, 1979). The concentration-response curve of the inhibitory effects of isoprenaline on phenylephrine-induced contractions was parabolic.…”

Section: Discussionsupporting

confidence: 93%

“…Low concentrations of isoprenaline inhibited contractile responses to field stimulation and to phenylephrine by an action on f3-adrenoceptors. This agrees with previous findings using this preparation (Ganguly & Bhattacharya, 1969;Vohra, 1979). The concentration-response curve of the inhibitory effects of isoprenaline on phenylephrine-induced contractions was parabolic.…”

Section: Discussionsupporting

confidence: 93%

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Effects of Metoclopramide and Isoprenaline in the Rat Vas Deferens; Interactions With Α‐adrenoceptors

Spedding

1980

British J Pharmacology

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3 From these results it is concluded that metoclopramide (2.8 to 280 pM) is a presynaptic a-adrenoceptor antagonist in the rat vas deferens.4 Following,-adrenoceptor blockade with (±)-propranolol (3.3 gM), (--isoprenaline (0.47 to 14 gM) inhibited responses to field stimulation but not to phenylephrine. These propranolol-resistant effects of isoprenaline were antagonized by metoclopramide (2.8 to 280 pM) and by phentolamine (0

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Section: Discussionsupporting

confidence: 93%

Section: Discussionsupporting

confidence: 93%

Effects of Metoclopramide and Isoprenaline in the Rat Vas Deferens; Interactions With Α‐adrenoceptors

Spedding

1980

British J Pharmacology

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“…The results obtained either in field-stimulated vas deferens or in organs contracted by barium chloride, support previous findings that the relaxation induced by f-adrenoceptor agonists are mediated by 12-adrenoceptors (Ganguly & Bhattacharya, 1969;Vohra, 1979;Lotti et al, 1980;Diaz-Toledo & Jurkiewicz, 1980;1990). This was indicated, according to Lands et al (1967), by the rank order of potencies for the agonists (Iso > Ad > NA), when the organ was electrically stimulated (Table 1) increase for isoprenaline and adrenaline potencies but the overall hierarchy was not substantially modified.…”

Section: Discussionsupporting

confidence: 89%

“…Almost all the results are based on functional antagonism against electrically-induced twitches (Ganguly & Bhattacharya, 1969;Vohra, 1979;Lotti et al, 1980;Diaz-Toledo & Jurkiewicz, 1980;1990).…”

Section: Introductionmentioning

confidence: 99%

“…As a consequence, our knowledge about the rank order of potency for Ad, NA and isoprenaline (Iso), which is one of the main tools for adrenoceptor classification, is still fragmentary. Although Vohra (1979) studied both agonists in the presence and absence of selective and non-selective fl-blockers, concentration-response curves and determinations of drug-receptor parameters were not performed, precluding a quantitative analysis and receptor characterization. (b) Data obtained by the use of the competitive antagonist propranolol vs. isoprenaline suggested that the fl-agents could be interacting with two receptors (Lotti et al, 1982).…”

Section: Introductionmentioning

confidence: 99%

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Different mechanisms of action of agents acting on β‐adrenoceptors in barium‐stimulated and electrically‐stimulated rat vas deferens

Diaz-Toledo

Jurkiewicz

1991

British J Pharmacology

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1 The relaxation induced by fl-adrenoceptor agonists in rat vas deferens was examined under two different experimental conditions: on electrically-induced twitch responses (35 V, 3 ms, 0.07 Hz), and on contractions induced by single doses of barium chloride (300pM). The experiments were performed in vasa of reserpine-treated rats, after blockade of a-adrenoceptors and extraneuronal uptake with dibenamine (10OpM, 30min), and neuronal uptake with cocaine (10,pM). 4 When twitch responses were used, and Ad or NA employed instead of Iso, the antagonists produced shifts of concentration-response curves which were smaller than expected from theory, precluding the determination of pKB values. This indicates that other mechanisms are involved besides an interaction with a single population of postsynaptic fl2-adrenoceptors.5 When barium chloride was used instead of twitch responses, although the potencies of Iso and Ad were increased respectively by about 30 fold and 5 fold, the rank order of potency was still consistent with an interaction with fl2-adrenoceptors. In addition, the antagonists produced parallel and concentrationdependent shifts of the curves of all the agonists, as expected from receptor theory. The values of pKB for a given antagonist were not modified by interchanging the agonists used, indicating a typical interaction with a single population of f2-adrenoceptors. When compared to the field-stimulated vas, the values of pKB for propranolol and IMA against isoprenaline were respectively 1.3 and 0.6 log units larger. These results suggest the fl-adrenoceptor agents act by different mechanisms of action in barium-stimulated and electrically-stimulated vas.6 It is suggested that when barium is used, the effects of agents acting on fl-adrenoceptors are mediated only by postsynaptic fl2-receptors, while other complicating factors, probably nerve-dependent presynaptic mechanisms, may be involved with electrical stimulation.

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Binding of agonists and antagonists to ?-adrenoceptors in rat vas deferens: relationship to functional response

May

Abel

Minneman

1985

Naunyn-Schmiedeberg's Arch. Pharmacol.

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The properties of beta-adrenoceptors in rat vas deferens were examined using radioligand binding assays of 125I-pindolol(125IPIN) and inhibition of electrically-evoked contractions of vas deferens in vitro. 125IPIN labelled a single class of high affinity binding sites with apparently mass action kinetics in membrane preparations of vas deferens with properties consistent with an essentially homogeneous population of beta 2-adrenoceptors. Isoprenaline inhibited electrically evoked (60 V, 1.0 ms, 0.1 Hz) contractions of vas deferens with an EC50 of 18.0 +/- 2.1 nM. KB values for antagonists in competitively antagonizing this response correlated well (r2 = 0.99) with the KD values for inhibition of 125IPIN binding. Inhibition of 125IPIN binding by isoprenaline, adrenaline, noradrenaline and salbutamol was determined under conditions designed to produce high and low affinity agonist binding. In the presence of 10 mM MgCl2, agonists inhibited specific 125IPIN binding with a relatively high potency and low Hill slope, while in the presence of 154 mM NaCl and 300 microM guanosine-5'-triphosphate, agonists inhibited specific 125IPIN binding with a lower potency and an apparent Hill slope closer to 1. To determine which affinity state was relevant to functional receptor stimulation, receptor density was decreased with bromoacetylalprenololmenthane (BAAM). Treatment of membrane preparations with 0.3 microM BAAM produced a 45% decrease in the Bmax for 125IPIN with no change in the apparent KD. Treatment of intact vasa deferentia with increasing concentrations of BAAM resulted in a progressive rightward shift in the dose-response curve to isoprenaline or salbutamol followed by a decreased maximum response. KA values for isoprenaline and salbutamol in activating the functional beta-adrenoceptors were compared with KI values for agonist inhibition of specific 125IPIN binding. The KA values for both agonists were not significantly different from the low affinity KI values, but were significantly different from the high affinity KI values. These data suggest that 1) a homogeneous population of beta 2-adrenoceptors inhibiting contraction of rat vas deferens can be labelled with 125IPIN, 2) there is a substantial beta-adrenoceptor reserve in rat vas deferens; and 3) the initial event in signal transduction by beta-adrenoceptors in rat vas deferens is the binding of agonists to the low affinity form of the receptor which is not complexed with the guanine nucleotide binding protein.

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Evidence for the presence of β2-inhibitory adrenoceptors in the rat vas deferens

Cited by 19 publications

References 4 publications

Effects of Metoclopramide and Isoprenaline in the Rat Vas Deferens; Interactions With Α‐adrenoceptors

Effects of Metoclopramide and Isoprenaline in the Rat Vas Deferens; Interactions With Α‐adrenoceptors

Different mechanisms of action of agents acting on β‐adrenoceptors in barium‐stimulated and electrically‐stimulated rat vas deferens

Binding of agonists and antagonists to ?-adrenoceptors in rat vas deferens: relationship to functional response

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