We describe here the development of an isolated hemisected adult spinal cord preparation suitable for use with the sucrose-gap technique for pharmacological studies of spinal circuitry in small mammals. Optimum conditions for viable activity and high-quality recordings are described together with examples of the use of this system to study the effect of the putative transmitter GABA and a known antagonist, bicuculline, on primary afferent terminal excitability and dorsal root potentials (DRP). Application of GABA to the spinal cord resulted in a depolarization of primary afferent terminals (PAD), which could be recorded in sucrose-gap as a DRP. This depolarizing potential was depressed but not eliminated by low Cl- ringer and was competitively antagonized by the application of varying concentrations of bicuculline. The results demonstrate both the viability and potential of this technique for pharmacological studies of adult mammalian spinal cord.