Substance P as a transmitter in the human ciliary muscle.

The present experiments, carried out on the human fresh ciliary muscle, were undertaken to define whether substance P is involved as an excitatory transmitter in the contractile response evoked by electrical stimulation. Our results show that, following cholinergic and adrenergic blockade, the resistant component of contraction was completely abolished by (D-Pro2-D-Trp7,9)-SP, a synthetic analogue of substance P with antagonistic activity. Moreover the effects of exogenous substance P were investigated.