An investigation of the actions of the calcium entry facilitator bay K 864 on the rat vas deferens

Hyland, Lisa; Warnock, Paula; Docherty, James R.

doi:10.1016/0014-2999(84)90414-x

Cited by 21 publications

(7 citation statements)

References 12 publications

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“…Verapamil was reported to increase the NE release in the rat vas deferens at concen trations around 10-5 M, probably by blocking the presynaptic a2-receptors (9). Bay k 8644 at 10-6-10-5 M, higher than that of the present study, was also shown to increase the NE release in the rat vas deferens (8,10); how ever, the increment was considered to be due to the activation of presynaptic calcium channels by Bay k 8644. Therefore, it is plausible to suppose in the present study that nifedipine and Bay k 8644 selectively affect the voltage-dependent calcium channels in the circular smooth muscle; on the other hand, verapamil may exert nonspecific actions in addition to blocking the calcium channels.…”

Section: Discussioncontrasting

confidence: 60%

“…In the present study, three calcium-entry modulators were used at concentrations be tween 10-8 M and 3x10-5 M. It has been reported that nifedipine at 10-5 or 5 X 10-4 M did not affect the nerve-stimulated release of [3H]-NE in the guinea pig and rat vas deferens (7,8). Verapamil was reported to increase the NE release in the rat vas deferens at concen trations around 10-5 M, probably by blocking the presynaptic a2-receptors (9).…”

Section: Discussionmentioning

confidence: 91%

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Effects of calcium-entry modulators on the biphasic neurogenic contractions in the circular muscle of guinea pig vas deferens.

Suzuki

Gomi

1989

Jpn.J.Pharmacol

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Abstract-Effects of nifedipine (10-8-10-6 M), verapamil (10-6-3X10-5 M) and Bay k 8644 (10-7 M) on the contractions induced by transmural nerve stimulation or agonists were investigated in the circular smooth muscle of guinea pig vas deferens using a ring preparation.Transmural Bay k 8644 slowed the relaxation of the tonic component, thereby prolonging the tonic component.Bay k 8644 also prolonged the duration of NE-induced contractions. These results, except for the con tradictory effects of verapamil between the phasic component and mATP-induced contractions, are consistent with the claim that ATP and NE are responsible for the generation of phasic and tonic component, respectively, in the circular muscle of guinea pig vas deferens.Recently, we have reported that the con tractions of the circular smooth muscle of the guinea pig vas deferens in response to trans mural stimulation and agonist drugs can be correctly recorded using the ring preparations (1 ). A train of stimulation with relatively high frequency (more than 20 Hz) produced biphasic contractions composed of initial phasic and secondary tonic components. Our results showed that the neurogenic con tractions of the circular muscle were not only due to norepinephrine but also clue to another transmitter, possibly ATP, although the con tractions were sympathetic in nature. We sug gested that ATP and norepinephrine co released from the sympathetic nerve terminals may be respectively responsible for the phasic and tonic component.to selectively inhibit the transmural stimu lation-induced phasic contractions and ATP induced contractions and has been used as a 't ool' drug to investigate the neurotransmis sion mechanism (2-6). Therefore, we have investigated the effect of nifedipine on the two components and have compared them with the effects on the 8,r-methylene ATP (mATP) and norepinephrine (NE)-induced contractions in order to ascertain the claim that ATP and norepinephrine are the transmit ters in the circular muscle of the guinea pig vas deferens. We also investigated the effects of verapamil and Bay IK 8644 for comparison. Materials and MethodsThe materials and methods used in the present study were substantially the same as those reported previously (1). In brief, ring preparations, approximately 2 mm in breadth,

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Section: Discussioncontrasting

confidence: 60%

Section: Discussionmentioning

confidence: 91%

Effects of calcium-entry modulators on the biphasic neurogenic contractions in the circular muscle of guinea pig vas deferens.

Suzuki

Gomi

1989

Jpn.J.Pharmacol

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“…the electrically stimulated 3H overflow was not enhanced by Bay K 8644 (10-7-3x10-5 M). This result is in agreement with the finding by Hyland et al (10) using the isolated rat vas deferens. Therefore, it may be assumed that there are differences in the number or properties of Ca2+ channels in the adrenergic nerve endings that are activated by the two modes of stimulation.…”

supporting

confidence: 94%

Effects of Bay K 8644 on the electrically evoked and KCl-evoked norepinephrine release and the corresponding contraction in isolated canine saphenous veins.

Takata

Kato

1987

Jpn.J.Pharmacol

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Abstract-Bay K 8644 caused no significant effects on the 3H overflow and con traction evoked by electrical stimulation in the canine saphenous vein preloaded with [3H]norepinephrine.Bay K 8644 significantly enhanced the 3H overflow evoked by 40 mM KCI in a concentration-dependent manner, which was antagonized by nisoldipine.Bay K 8644 failed to significantly augment the KCI-evoked con traction.These results suggest that there is a difference between the modes of action of Bay K 8644 on norepinephrine releases evoked by electrical stimulation and KCI.

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“…Both the maximum direct contraction to amidephrine and the maximum potentiation of the contraction to a single stimulus pulse were significantly reduced in prostatic portions of the vas deferens of SHR. These actions ofamidephrine are al-adrenoceptor mediated since: (a) other al-agonists have similar actions (cirazoline, Docherty & McGrath, 1982;phenylephrine, MacDonald & McGrath, 1980), whereas x2-selective agonists, such as xylazine, do not normally have these actions (Hyland et al, 1984); (b) prazosin antagonizes the potentiation in a competitive manner (Docherty & McGrath, 1982); (c) Pbz antagonizes the potentiation in a noncompetitive manner; (d) rauwolscine did not antagonize the potentiation in concentrations that produce a2-adrenoceptor blockade (Docherty, 1984a and present results). The potentiation of stimulation-evoked contractions by ax,-adrenoceptor agonists is postjunctionally mediated since: (a) potentiation occurs in the concentration range in which these agonists produce intermittent direct contractions of the smooth muscle (MacDonald & McGrath, 1980;and present (Yamada et al, 1980;Woodcock & Johnson, 1980), although not in SHR (Hicks et al, 1983).…”

Section: Discussionmentioning

confidence: 99%

An investigation of α‐adrenoceptor responsiveness in the vas deferens of spontaneously hypertensive rats

Docherty

Warnock

1985

British J Pharmacology

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1ax-Adrenoceptor-mediated responses were investigated in isolated vasa deferentia from spontaneously hypertensive rats (SHR) and normotensive Wistar rats (NWR). 2 There was no significant difference between NWR and SHR in the inhibition of the isometric contraction to single pulse field stimulation by M2-selective agonists in prostatic portions, nor by 2-selective agonists and the al-selective agonist, amidephrine in epididymal portions in the presence of nifedipine to prevent postjunctional actions of a-1-selective agonists.3 There was no significant difference between NWR and SHR in the potency of amidephrine in causing a postjunctionally mediated potentiation of the isometric contraction to single pulse field stimulation in prostatic portions but the maximum potentiation was significantly reduced in SHR. However, the maximum potentiation of the isometric contraction by the calcium entry facilitator, Bay K 8644, was not significantly different between NWR and SHR. The maximum direct contraction to amidephrine, but not to Bay K 8644, was also significantly reducd in SHR. 4 The irreversible a,-adrenoceptor antagonist, phenoxybenzamine was more potent in SHR than NWR in reducing the maximum potentiation by amidephrine of the stimulation-evoked isometric contraction and in reducing the maximum direct contraction to amidephrine. 5 It is concluded that there is a reduced postjunctional a,-mediated responsiveness in the vas deferens of SHR due probably to a reduction in receptor number.

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An investigation of the actions of the calcium entry facilitator bay K 864 on the rat vas deferens

Cited by 21 publications

References 12 publications

Effects of calcium-entry modulators on the biphasic neurogenic contractions in the circular muscle of guinea pig vas deferens.

Effects of calcium-entry modulators on the biphasic neurogenic contractions in the circular muscle of guinea pig vas deferens.

Effects of Bay K 8644 on the electrically evoked and KCl-evoked norepinephrine release and the corresponding contraction in isolated canine saphenous veins.

An investigation of α‐adrenoceptor responsiveness in the vas deferens of spontaneously hypertensive rats

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