A comparative study on contractile responses of rabbit and guinea pig vasa deferentia to electrical field stimulation

Contractile responses of rabbit and guinea pig vasa deferentia to electrical field stimulation (EFS) are compared. A muscarinic receptor blocking agent, 1 microM atropine markedly reduced phasic and tonic contraction induced by EFS (20 Hz, 0.5 msec, 30 V, for 30 sec) in rabbit vas deferens, while it only slightly depressed those in guinea pig vas deferens. Further addition of an adrenergic alpha1 receptor blocking agent, 1 microM prazosin markedly depressed the second tonic contraction in both rabbit and guinea pig vasa deferentia. In the presence of atropine and prazosin, further addition of a P2X purinoceptor desensitizing agent, 10 microM alpha,beta-methylene ATP (alpha, beta-MeATP) abolished the residual phasic contractile response in guinea pig vas deferens, while it partially depressed that in rabbit vas deferens. The administration of 10 microM alpha,beta-MeATP in the absence of atropine and prazosin markedly potentiated the phasic contractile response of rabbit vas deferens to EFS, while it depressed that of guinea pig vas deferens. Contractile response of rabbit vas deferens to alpha,beta-MeATP was more potent than those of ATP and 2-methyl-thioATP (2-Me-thioATP), while these nucleotides had almost same potency in guinea pig vas deferens. These findings may indicate that contribution of cholinergic, adrenergic and purinergic neurotransmission to the contractile response of rabbit vas deferens to EFS is different from that of guinea pig vas deferens.