Dilatation in the carotid vascular territory of the cat in response to activation of cell bodies in the locus coeruleus.

Electrical stimulation of the locus coeruleus in the monkey results in a frequency-dependent vasoconstriction in the internal carotid circulation, and a frequency-dependent vasodilatation in the external carotid circulation. In the cat we have studied the extracerebral vasodilator response using electrical stimulation at appropriately high frequencies. Further investigations reported here demonstrate that 1-glutamate, a non-specific neuronal excitant, reproduces the dilator response in the cat. This clearly shows that the response to electric stimulation of the locus coeruleus, previously reported, is due to excitation of cell bodies rather than fibres of passage.