Effects of substance P on sympathetic preganglionic neurones

Antidromically identified sympathetic preganglionic neurones, located in the second thoracic segment of the rat spinal cord, were tested for their response to iontophoretically applied substance P. Substance P increased the firing rate of both 'spontaneously' active and glutamate-activated neurones. As substance P-like immunoreactivity is present in the intermediolateral cell column of the thoracic spinal cord, it is concluded that substance P may be an excitatory transmitter or modulator involved in mediating excitatory drive to sympathetic preganglionic neurones.