Suppression of receptive and proceptive behavior in ovariectomized, estrogen-progesterone-primed rats by intraventricular beta-endorphin: studies of behavioral specificity.

Intraventricular (i.c.v.) administration of beta-endorphin (beta-END) has been shown to suppress lordosis behavior in ovariectomized (OVX) estrogen-progesterone (EP) primed rats, but the behavioral specificity of this effect is not known. Using OVX EP-primed rats, the present study assessed the effect of i.c.v. beta-END on proceptive behavior as well as on lordosis (receptive) behavior, and attempted to discern whether the sexual effects were secondary to generalized nonspecific behavioral effects. Doses of 0.5-4 micrograms beta-END (human) significantly suppressed lordosis behavior. Doses of 1 and 4 micrograms were used in experiments which measured proceptive behaviors (presentations and ear wiggling), and both doses abolished or nearly abolished the display of these behaviors. Administration of inactive peptide (a protein digest) had no effect on sexual behavior. Neither 1 nor 4 micrograms beta-END elicited measurable catalepsy. In a series of tests for responsiveness to general somatosensory stimuli, 1 microgram had no effect on responsiveness while 4 micrograms had minor effects, even though sexual activity was severely diminished after both doses. Blood pressure was unaltered by infusion of beta-END (1 microgram), although there was a significant reduction in heart rate. When open field behavior was tested in conjunction with sexual behavior, ambulation and rearing were significantly decreased after beta-END treatment as compared with saline treatment. However, simple linear correlation tests showed a lack of correlation between the changes in open field behavior and the changes in sexual behavior, indicating that the effects of beta-END on the two types of behavior may be unrelated.(ABSTRACT TRUNCATED AT 250 WORDS)