Neural control of the middle ear mucosa.

Neurogenic inflammation is assumed to be an important local defence mechanism against noxious stimuli in various parts of the body. Recent experimental evidence suggests substance P(SP) to be the mediator of this mechanism in the respiratory tract. Immunohistochemically, SP has earlier been reported to be present in the middle ear mucosa of the cat and guinea pig. Our earlier study demonstrated SP-like immunoreactive (SPLI) nerve fibres in the middle ear mucosa and tympanic nerve of the rat, guinea pig and man. This study shows that in experimental animals, many neuron cell bodies of the sensory ganglia of the glossopharyngeal nerve show SPLI. It is suggested that SP may be involved in the neurogenic inflammatory reaction leading to the mucosal middle ear disease.

Is substance P the neurotransmitter in the vestibular end organs?

The vestibular end organs of the rabbit were fixed intracardially with phosphate buffered 4% formaldehyde, sectioned for 15 micron cryostat sections and incubated with monoclonal substance P (SP) antibody. Specific SP-like immunoreactivity (SPLI) was observed within and below the sensory epithelia of both utricular and saccular maculae and ampullary cristae. Particularly strong SPLI was seen in the maculae which showed many SPLI-positive axons in the subepithelial space and a network of SPLI-positive structures in the basal zones of the sensory epithelium. The calyceal terminals of type I hair cells showed regularly SPLI. The possibility of a transmitter or modulator role for SP in the vestibular function is suggested.