Tail pinch vs. cervical probing: Opposite effects upon intracranial reinforcement in female rats

Tail pinch, that is, the application of mild pressure to the base of a rat’s tail for a brief period, has been shown to facilitate a variety of dopamine (DA) dependent motivated behaviors, among them feeding, sexual activity, and intracranial reward (intracranial self-stimulation, ICS). Antelman, Caggiula, and their co-workers have presented a theory of nigro-neostriatal function in which tail pinch and cervical probing, a procedure consisting of the brief application of mild pressure against the wall of the cervix, respectively facilitate and inhibit behavioral activity through opposite effects upon DA cells within the substantia nigra (A9). We tested this model further using A9 implanted female rats responding for ICS. Tail pinch facilitated ICS response rates, while cervical probing reduced them. This is consistent with previously reported behavioral and electrophysiological evidence and with the hypothesized model in which increased and decreased nigrostriatal function serves to activate or suppress behaviors.