Variations in blood flow on mandibular glandular secretion to autonomic nervous stimulations in anesthetized dogs

Abstract

1. Continuous stimulation of the preganglionic parasympathetic nerve (the ramus communicans of the mandibular ganglion) for 1-2 min at supramaximal voltage (5 V) and pulse duration (1 ms) increased salivary gland arterial inflow and this was accompanied by copious salivary secretion. The responses were recorded continuously during the period of stimulation. The frequency for initiating the responses was 0.5 Hz. Maximal responses occurred at 16 Hz. The response coefficient of arterial inflow to stimulus frequency was 0.17 ml min-1 g-1 Hz-1 and that of secretion to stimulus frequency was 0.016 ml min-1 g-1 Hz-1. 2. The secretory response to low and moderate levels of parasympathetic nerve stimulation (below 8 Hz) was not affected by a reduction or cessation in aterial inflow whereas the response to high level parasympathetic nerve stimulation (above 8 Hz) was significantly alleviated if blood flow to the gland was maintained (via controlled vascular perfusion) at a level less than that of the resting arterial inflow. However, when the gland was already secreting near-maximally (stimulated at 8 Hz), sudden cessation of blood flow for a short period of time (0.5-2 min) had no effect on the salivary flow. 3. Continuous stimulation of the cervical sympathetic nerve for 1-2 min at supramaximal voltage (20 V) and pulse duration (1 ms) decreased arterial inflow and this was accompanied by scanty salivary secretion. The vascular response persisted during the period of stimulation. The secretory response was 15 s late in onset and might continue for 1 min after stimulation. The frequency for inititating the responses was 1-4 Hz. Maximal responses occurred at 16-32 Hz. The response coefficient of arterial inflow to stimulus frequency was -0.04 ml min-1 g-1 Hz-1 and that of salivary secretion to stimulus frequency was 0.001 ml min-1 g-1 Hz-1. 4. The secretory response to sympathetic nerve stimulation at different frequencies in glands with blood flow maintained at resting rate (via controlled vascular perfusion) resembled that in glands with spontaneous blood flow. 5. Sympathetic nerve stimulation was found to retard salivary secretion caused by parasympathetic stimulation, irrespective of whether the gland received spontaneous arterial inflow or controlled vascular perfusion at a resting flow rate. 6. The results suggest that the salivary secretion to stimulation of parasympathetic nerve is independent of blood flow over a wide range of stimulus frequencies; however, the response to high frequency stimulation of the parasympathetic nerve may be affected by fluctuations in blood flow. Retardation of parasympathetic-induced salivary flow by superimposed sympathetic nerve stimulation may not be related to blood flow changes.