Effects of adrenaline on nerve terminals in the superior cervical ganglion of the rabbit

Abstract

1 Adrenaline decreases the release of transmitter from the presynaptic nerves in the superior cervical ganglion of the rabbit. The presynaptic mechanism of adrenaline action was investigated with micro-electrode techniques. 2 Adrenaline (10⁻⁵M) did not change the threshold of the presynaptic nerve terminals to a current stimulus. 3 The effect of adrenaline on the excitatory postsynaptic potential (e.p.s.p.) was decreased when the calcium concentration of the perfusing solution was increased to 10 mm. 4 The effect of adrenaline on a train of e.p.s.ps (30–50 Hz) was analysed. Adrenaline decreased the readily available stores of transmitter, but only slightly changed the probability of release. 5 The probability of release was increased when the calcium concentration was increased to 5 mm. 6 It was concluded that adrenaline acts directly on excitation release coupling in the presynaptic terminals.