抄録
Salivary secretion is reflexly evoked by taste and mechanical stimulation of the oral region. Flow rate of saliva is mainly regulated by the parasympathetic nerve innervating the salivary glands. In the present study we undertook in vivo and in vitro experiments for analyzing activity of the parasympathetic neurons innervating the submandibular gland of rats. The following results were obtained: 1) vigorous salivary secretion was produced by electrical stimulation of the parasympathetic nerve at a frequency of 10-20 Hz, which corresponds to salivation when rats chewed foodstuffs, groomed, and were exposed to heat; 2) the preganglionic parasympathetic nerve showed reflex responses to taste and mechanical stimulation applied to the oral region, tonic firing (5-29 Hz), and phasic firing (up to 50-80 Hz); 3) we also studied activity of the superior salivatory neurons (soma of the parasympathetic nerve) in brainstem slice preparations of neonatal rats using the whole-cell patch-clamp technique, and found the tonic firing pattern and phasic firing pattern; 4) the latter firing pattern was invariably found in the neurons innervating the anterior part of the tongue, which are responsible for vasodilatation; 5) the superior salivatory neurons received glutamatergic excitatory synaptic inputs, and the NMDA component was larger than the non-NMDA component in the neurons innervating the salivary glands. These characteristics may be involved in determining the tonic and low firing properties of the parasympathetic nerve innervating the salivary glands. [Jpn J Physiol 54 Suppl:S12 (2004)]
