Cholinergic component of the excitatory response in the rat anococcygeus muscle

The effects of neostigmine and atropine on the excitatory response of the rat anococcygeus muscle to field stimulation have been studied. The excitatory responses were inhibited and abolished by 0.1 and 3 micro M phentolamine, respectively. Neostigmine, 1 micro M, by itself and in the presence of 0.1 micro M phentolamine potentiated responses. In the presence of 3 micro M phentolamine neostigmine restored responses to 1-20 HZ. Atropine, 1 micro M by itself, in the presence of neostigmine (1 micro M), and in the presence of neostigmine and phentolamine (0.1 micro M) inhibited the response. Hexamethonium, 100 micro M, had no effect on responses to field stimulation or to exogenously applied (-)-noradrenaline. Responses to (-)-noradrenaline were not altered by neostigmine or atropine. It is suggested that there is a cholinergic component to the excitatory response to field stimulation in the rat anococcygeus muscle.