L. Marson et Ke. Mckenna, STIMULATION OF THE HYPOTHALAMUS INITIATES THE URETHROGENITAL REFLEX IN MALE-RATS, Brain research, 638(1-2), 1994, pp. 103-108
The urethrogenital (UG) reflex is a spinal sexual reflex which is toni
cally inhibited in the intact male rat by neurons in the nucleus parag
igantocellularis (nPGi). The medial preoptic area of the hypothalamus
(MPOA) is involved in the activation of male sexual behavior. The pres
ent study examines the effect of hypothalamic stimulation on the UG re
flex in the intact male rat. Areas of the hypothalamus were stimulated
bilaterally with either electrical stimulation or D,L-homocysteic aci
d (DLH) and the presence of the UG reflex examined. Stimulation of dis
crete areas of the hypothalamus evoked the UG reflex. The UG reflex co
uld be initiated in the absence of genital stimulation. Microinjection
s of DLH into the MPOA also initiate the UG reflex. These data suggest
that stimulation of neurons in the MPOA overcome the inhibition by th
e nPGi and facilitate spinal genital reflexes leading to ejaculation.