Summary. Female Albino Swiss rats were exposed to 5α-dihydrotestosterone benzoate (DHTB) for the last 4 days of gestation, or for 4 days after birth, or both. Post-natal DHTB exposure (as well as pre- plus post-natal exposure) resulted in a 2–3-fold increase in the number of motor neurones forming the spinal nucleus of bulbocavernosus (SNB); numbers were intermediate between those found in normal females (∼40) and males (∼200). These DHTB-treated groups also possessed perineal muscles which were ∼25% of the weight of those in normal males. Transverse sections of one of the muscles (levator ani) showed that it had approximately half the muscle fibres of normal males. Females exposed prenatally to DHTB showed a small (but significant) rise in SNB numbers, but had no recognizable perineal muscles.
Keywords: neonate; motor neurones; hormones: perineal muscles; rat