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Effects of alpha,beta-methylene ATP on biphasic responses of rat vas deferens
Abstract:
The epididymal region of isolated vas deferens of the rat was stimulated locally with field electrodes. Continuous perfusion with alpha,beta-methylene-adenosine-5'-triphosphate (mATP, 10(-5) M) desensitized the P2-purinoceptors and the effect of this on the two components of tetanic responses and the 'non-adrenergic' and adrenergic phases of single shock responses were examined. Exposure to mATP selectively prevented the contractions to adenosine-5'-triphosphate (ATP, 10(-4)-5 X 10(-4) M) but not noradrenaline (NA, 10(-5) M) and preferentially blocked the secondary but not the primary tetanic component. It also depressed markedly the non-adrenergic phase of single shocks and either reduced or abolished the adrenergic phase. Thus the secondary tension development depends in the rat vas deferens on both the activation of alpha 1-adrenoceptors and the non-adrenergic twitch mechanism. The action of mATP involves more processes than the desensitization of the P2-purinoceptors so does not positively identify purinergic transmission. Direct NA-induced contraction contributes more to the primary than to the secondary tetanic component.
Insights
Alpha,beta-methylene-adenosine-5'-triphosphate (mATP) desensitizes P2-purinoceptors in rat vas deferens, impacting both adrenergic and non-adrenergic responses. This suggests complex mechanisms beyond purinergic transmission in smooth muscle contraction.
Area of Science:
- Pharmacology
- Physiology
- Neuroscience
Background:
- The rat vas deferens exhibits complex contractile responses to electrical stimulation.
- Purinergic and adrenergic signaling pathways are implicated in smooth muscle function.
- Understanding these pathways is crucial for elucidating mechanisms of contractility.
Purpose of the Study:
- To investigate the role of P2-purinoceptors in rat vas deferens contraction.
- To differentiate the contributions of purinergic and adrenergic signaling.
- To characterize the effects of alpha,beta-methylene-adenosine-5 -triphosphate (mATP) on contractile responses.
Main Methods:
- Isolated rat vas deferens preparation.
- Field electrode stimulation.
- Perfusion with alpha,beta-methylene-adenosine-5 -triphosphate (mATP) and adenosine-5 -triphosphate (ATP).
- Assessment of contractile responses to ATP and noradrenaline (NA).
Main Results:
- mATP selectively desensitized P2-purinoceptors, blocking ATP-induced contractions.
- mATP preferentially inhibited the secondary component of tetanic responses.
- mATP markedly depressed the non-adrenergic phase and reduced/abolished the adrenergic phase of single shock responses.
- Direct noradrenaline (NA) contraction contributed more to the primary than secondary tetanic component.
Conclusions:
- Secondary tension development in rat vas deferens involves both alpha 1-adrenoceptor activation and a non-adrenergic twitch mechanism.
- The action of mATP suggests processes beyond simple P2-purinoceptor desensitization, complicating the identification of purinergic transmission.
- Distinct contributions of adrenergic and non-adrenergic pathways to different phases of contraction were elucidated.