Purinergic Modulation of Ocular Muscle Contraction

The problem of purinergic regulation in synapses of phasic and tonic muscles of warm-blooded animals has been investigated. For this purpose, the effect of the cotransmitter of the main mediator, ATP, and its persistent metabolite, adenosine, on the contraction of various oculomotor systems of the rat, the lateral rectus (tonic) and circular (phasic) muscles of the eye, has been evaluated. ATP potentiated the carbacholine-evoked contraction of the rat lateral rectus muscle by one-quarter, while this purine, on the contrary, significantly inhibited the carbacholine-evoked contraction of the circular eye muscle. No significant manifestation of the modulatory effect of adenosine on the carbacholine-evoked contraction of the muscles under study was revealed. These results indicate a multidirectional postsynaptic effect of ATP on phasic and tonic oculomotor systems.