Prolonged discharge of wide-dynamic-range spinal neurons evoked by formaldehyde injected in their cutaneous receptive...

In decerebrate, unanesthetized cats, subcutaneous injection of formaldehyde solutions (0.05 ml, 2.5%) in the receptive fields of spinal wide-dynamic-range neurons elicited an immediate and continuous discharge or burst activity in the neurons that lasted 10 to 55 min. This discharge was reduced by conditioning stimulation of the medial raphe nucleus and was completely abolished by morphine (3 mg/kg, i.v.). Low-threshold cutaneous mechanoreceptive neurons in the dorsal horn and dorsal column nuclei did not show a sustained response.