Effects of Estrogen Treatment on the Size of Receptive Field and Response Threshold of Pudendal Nerve in the Female Rat

Receptive fields and response thresholds were determined by stimulation with a camel hair brush and von Frey hairs during recording from a specific branch of the pudendal nerve, in untreated and estrogen-treated ovariectomized female rats. The receptive field of this pudendal nerve branch is located on the perineal skin of the female rat, extending in some cases onto the back of the leg. Estrogen treatment caused an expansion of the receptive field, and a trend toward increased receptor sensitivity within the receptive field. The estrogen effect is appropriate to the type of stimulation applied by the male rat during induction of the lordosis response: pelvic thrusting by the male contacts the area of the female’s skin included in this receptive field and should result in phasic responses, which we find to be estrogen-sensitive, rather than tonic, long-sustained responses, which are not estrogen-sensitive. In these pudendal nerve recordings, there were considerable overlaps between estrogen-treated and untreated groups both in receptive field size and sensitivity. Unless specific, strongly estrogen-sensitive receptors have been partially masked by our stimulation and recording methods, it does not seem likely that this peripheral, somatosensory estrogen effect could by itself account for the overall estrogen effect upon the lordosis reflex.