Neuromedin N decreases self-stimulation of the medial prefrontal cortex.

Intracerebral microinjections of neurotensin (NT) decrease intracranial self-stimulation (ICSS) of the medial prefrontal cortex (MPC) in the rat. This effect could be due to the ability of NT to bind dopamine. To test this hypothesis we studied the effects of intracerebral microinjections of neuromedin N, a natural NT analogue that does not bind dopamine, on ICSS of the rat MPC. Unilateral microinjections of neuromedin N into the MPC at doses of 2.5, 5, 10, 20 and 40 nmol produced a dose-related decrease in ICSS of the ipsilateral MPC. ICSS of the contralateral MPC, used as a control, was not affected by the microinjections. These results suggest that the inhibitory effect of NT on ICSS is independent of NT-dopamine binding. Because neuromedin N is also present in the MPC, these results also suggest a possible neuromodulatory role of this neuropeptide on ICSS of the prefrontal cortex.