IRRADIATION INFLUENCES THE EXPRESSION OF SUBSTANCE-P AND ENKEPHALIN IN THE RAT LARYNX

The effects of radiotherapy on neuropeptide expression in the rat lary nx were studied. Irradiation was given for five days, 6 or 8 Gray dail y. Ten days after the end of irradiation, the larynx, the laryngeal ne rves and different ganglia related to the larynx were dissected out fr om irradiated and control animals and processed for neuropeptide immun ohistochemistry. There was an increased immunolabelling for two of the neuropeptides tested, substance P and enkephalin, in the innervation of the subglottic glands and in the acetylcholinesterase-positive gang lionic cells of the local ganglia. These cells were interpreted as rep resenting postganglionic parasympathetic ganglionic cells. The changes seen in the subglottic glands were interpreted as most likely being r elated to the changing pattern of staining seen in the local ganglia. No changes in substance P- and enkephalin expression were observed in other laryngeal structures, the nodose ganglia, superior cervical gang lia or laryngeal nerve paraganglia. Thus, in certain respects neuropep tide expression in the larynx is modulated by radiotherapy. Since neur opeptides have both neurotransmitter and/or neuromodulator effects in airway tissue and since they show effects as growth factors, the occur rence of this plasticity in neuropeptide expression should be taken in to consideration in future studies examining the effects of irradiatio n on normal/diseased airway tissues.