Search

4 pages

(1) The subject of this thesis was the investigation of the dual innervation of the anococcygeus muscle. The rat anococcygeus had previously been shown in vitro to have a motor adrenergic innervation and also an inhibitory nerve response whose transmitter was unknown. (2) The object of the present study was threefold - (a) To determine whether this inhibitory response was due to a nerve pathway distinct from the motor innervation and with a separate spinal origin and if so whether this pathway had a ganglion synapse and so could be considered as part of the autonomic nervous system. (b) To compare the pharmacological properties of the anococcygeus muscle and vas deferens and to determine whether the rate of depletion of noradrenaline by reserpine in these two tissues was affected by nerve stimulation. (c) To compare the properties of the anococcygeus muscles from the cat and the rat in order to find whether the dual innervation found in the rat was represented in this further species and if so whether this comparison would throw any more light on the nature of the inhibitory response. (3) Using a pithed rat preparation permitting selective stimulation of the autonomic spinal outflows, it was shown that the inhibitory pathway to the anococcygeus muscles arose from the spinal canal, that it was interrupted by a ganglion synapse and that the spinal origin of its preganglionic nerves was L5 - S2 as opposed to T10 - L3 for the preganglionic nerves in the motor pathway. (4) Using this same preparation, the pharmacological properties of the motor nerves to the anococcygeus were examined in situ and compared with those of the vas deferens. This comparison demonstrated that the pharmacological properties of the anococcygeus motor innervation were those of a classical adrenergic innervation whereas the vas deferens showed responses which were in themselves complex and showed unconventional responses to drugs. A hypothesis is suggested to explain this unconventional nature of