Cyclobenzaprine effects on locus coeruleus cells in tissue slice

Tissue slices 400 μ thick were taken from the brain stem, at the level of the locus coeruleus, of 150–250 g Sprague-Dawley rats. Microe1ectrodes were placed in the locus coeruleus under visual control, and a cell whose discharge rate would decrease with microiontophoretic application of norepinephrine or clonidine was sought. Cyclobenzaprine (CBZ) was then introduced into the perfusion medium at a concentration equivalent to 1 mg/kg body weight of the whole animal. Discharge rates before and during CBZ administration were compared. The six cells with initial discharge rates between 2 and 10 Hz decreased firing with CBZ, whereas the four cells with initial rates between 0.5 and 1.5 Hz increased their rates with CBZ.