Immunohistochemical evidence of nNOS and changes after intraglandular application of botulinum toxin A in cephalic salivary glands of adult rats.

The purpose of our study was to investigate the possible influence of local injections of botulinum toxin A on the activity of neuronal nitric oxide synthase (nNOS) in cephalic salivary glands of adult rats. The role of nitric oxide (NO) as a possible neuromodulator of vascular regulation and in particular regulation of secretion in the upper respiratory and aerodigestive tract is discussed. We present immunohistochemical evidence of nNOS in the salivary glands of female adult Wistar rats, both in native (untreated) glands and after intraglandular injection of botulinum toxin A under general anesthesia. Other than in the untreated glands, there was a significant decrease in nNOS in the treated organs which became stronger with extended toxin exposure time. After our laboratory had already shown a decrease in acetylcholinesterase immunoreactivity after injection of botulinum toxin A into the cephalic salivary glands of the rat, the present study discusses a possible participation of NO in the regulation of secretion from these organs. As a conclusion, it might be assumed that the influence of botulinum toxin A on nNOS in the cephalic salivary glands of the rat is able to explain the sometimes longer duration of the toxin effect at the neuroglandular junction than at the motor endplate.