The effect of chronic antipsychotic treatment on sexual behaviour, hormones and organ size in the male rat.

Antipsychotic drug-induced sexual dysfunction is an important and problematic side effect. We have investigated the effect of chronic antipsychotic treatment on sexual behaviour, sex hormones and genital organ size in the male rat. The following sexual functions were significantly impaired in both risperidone (2 mg/kg) and haloperidol (2 mg/kg) groups at 3 weeks: libido (assessed in mounting frequency and intromission), sexual arousability/motivation (in terms of latencies for mounting and intromission) and orgasm (in terms of latency for ejaculation). At 6 weeks, haloperidol also suppressed the 'hit ratio' (intromissions/mounts) as well as the above-mentioned parameters indicating erectile dysfunction. Risperidone had no significant effect on sexual function at 6 weeks. Compared with the control group, haloperidol and risperidone decreased the serum level of testosterone after 6 weeks but not after 3 weeks. The two drugs did not influence the serum level of leutenizing hormone (LH). At 3 weeks, the epididymis was significantly decreased below controls in both risperidone and haloperidol groups. At 6 weeks, the epididymis, seminal vesicle and prostate weights were significantly reduced in the haLoperidol group, but not in the risperidone group. The serum concentration of testosterone significantly correlated with sex organ weight, but not with sexual behaviours. These results suggest that sexual function, testosterone levels and genital tissue size in male rats were affected to different degrees by risperidone and haloperidol. These findings contribute to our understanding of antispsychotic drug-induced male sexual dysfunction.