1. 1. Cardiac adrenergic receptors in snakes were examined using an isolated atria preparation of Naja naja and Ptyas korros. Treatments included an examination of the atrial responses to selective α- and β-adrenergic agonists and antagonists. 2. 2. In both species, both phenylephrine and isoproterenol produced dose-dependent increases in the atrial beating rate and tension. Phenylephrine-induced increases were characterized with a high affinity and low affinity components. 3. 3. These positive chronotropic and inotropic effects produced by phenylephrine and isoproterenol were abolished with propranolol and in the phenylephrine-induced response phentolamine also attenuated the low affinity response and blocked the high affinity response. 4. 4. With catecholamines depletion via 6-OH dopamine or reserpine, the high affinity component in the phenylephrine-induced response was no longer observed. 5. 5. It is concluded that β-adrenoceptors are the predominant post-synaptic adrenoceptors in snake atria. Stimulatory presynaptic α-adrenoceptors for modulating noradrenaline release may also be present.
|Original language||English (US)|
|Number of pages||6|
|Journal||Comparative Biochemistry and Physiology. Part C, Comparative|
|State||Published - 1985|
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