Evidence for peripeduncular neurons having a role in the control of feminine sexual behavior in the rat

In order to test the hypothesis that peripeduncular nucleus (PPN) cells are essential for normal sexual behavior, synaptic blockade in the chronically implanted awake animal was attempted by means of the local injection of pentobarbital (PB) at a concentration which may interfere with synaptic transmission without affecting conduction in fibers. Ovariectomized, female rats were chronically implanted with cannulae directed to the PPN or the dorsal midbrain. After adequate estrogen priming, rats were injected with 22 mM pentobarbital (PB) or artificial cerebrospinal fluid (ACSF). Seven min after PB injection in PPN lordosis quotient was significantly lowered, whereas PB in dorsal midbrain or ACSF in PPN had no effect. It is concluded that PPN neurons themselves may have a functional role in the control of lordosis and that loss of PPN neurons may account for impairment of reproductive behavior observed after lesions in the ventrolateral midbrain.