Parasympathetic tonic dilatory influences on cerebral vessels

Abstract

Parasympathetic nerves from the pterygopalatine ganglia may participate in development of cluster headaches, in vascular responses to hypertension and in modulation of damage due to stroke. Stimulation of the nerves elicits cerebral vasodilatation, but it is not known if the nerves tonically influence cerebrovascular tone. We hypothesized that parasympathetics provide a tonic vasodilator influence and tested that hypothesis by measuring cerebral blood flow in anesthetized rats before and after removal of a pterygopalatine ganglion. Ganglion removal led to reduced cerebral blood flow without changing blood pressure. Thus, parasympathetic nerves provide tonic vasodilatory input to cerebral blood vessels.

Fig. 1

In this representative animal arterial pressure (AP), mean AP (MAP), and heart rate (HR) did not change from the basal state prior to removal of the PPG (left) when compared with a period approximately 5 minutes after removal of the left PPG (right). Cerebral blood flow (CBF) did fall after removal of the ganglion ipsilateral to the ganglionectomy. Note: CBF was recorded on a strip chart generated from a laser flowmeter (Laserflo BPM 403A, TSI, St. Paul, MN) while AP and HR were recorded and saved electronically on a Power Lab system (Model 16sp, ADInstruments, Colorado Springs, CO). The two were synchronized post hoc for purposes of displaying all data in this image.