Elsevier

Biological Psychiatry

Volume 67, Issue 12, 15 June 2010, Pages 1199-1204
Biological Psychiatry

Archival Report
Lesions of the Medial Prefrontal Cortex Cause Maladaptive Sexual Behavior in Male Rats

https://doi.org/10.1016/j.biopsych.2009.12.029Get rights and content

Background

An inability to inhibit behaviors once they become maladaptive is a component of several psychiatric illnesses, and the medial prefrontal cortex (mPFC) was identified as a potential mediator of behavioral inhibition. The current study tested if the mPFC is involved in inhibition of sexual behavior when associated with aversive outcomes.

Methods

Using male rats, effects of lesions of the infralimbic and prelimbic areas of the mPFC on expression of sexual behavior and ability to inhibit mating were tested using a paradigm of copulation-contingent aversion.

Results

Medial prefrontal cortex lesions did not alter expression of sexual behavior. In contrast, mPFC lesions completely blocked the acquisition of sex-aversion conditioning and lesioned animals continued to mate, in contrast to the robust behavioral inhibition toward copulation in mPFC intact male animals, resulting in only 22% of intact male animals continuing to mate. However, rats with mPFC lesions were capable of forming a conditioned place preference to sexual reward and conditioned place aversion for lithium chloride, suggesting that these lesions did not alter associative learning or sensitivity for lithium chloride.

Conclusions

The current study indicates that animals with mPFC lesions are likely capable of forming the associations with aversive outcomes of their behavior but lack the ability to suppress seeking of sexual reward in the face of aversive consequences. These data may contribute to a better understanding of a common pathology underlying impulse control disorders, as compulsive sexual behavior has a high prevalence of comorbidity with psychiatric disorders and Parkinson's disease.

Section snippets

Animals

Adult male (250–260 g) Sprague–Dawley rats obtained from Harlan Labs (Indianapolis, Indiana or Charles River, Quebec, Canada) were housed individually in an artificially lighted room on a reversed light/dark cycle (12:12 hours, lights off at 10:00 am) at a temperature of 72°F. Food and water were available at all times. Ovariectomized, estrogen (subcutaneous silastic capsule with 5% 17-beta-estradiol benzoate) and progesterone (subcutaneous injection 500 μg in .1 mL of sesame oil) primed female

Sexual Behavior

Prelimbic/IL lesions did not affect any sexual parameter tested in male rats that were sexually naive before surgery (Figure 1D–F). In agreement, no effects of PL/IL lesions on sexual behavior were detected in the sexually experienced male rats included in the conditioned sex aversion experiment during the first trial, hence before pairing of LiCl with sexual behavior (Table 1). Hence, PL/IL lesions did not affect sexual behavior independent of sexual experience.

Elevated Plus Maze

In agreement with prior reports (

Discussion

In this study, we report that lesions of the IL and PL regions of the mPFC do not affect the expression of sexual behavior nor the acquisition of a conditioned place preference to sexual reward. Instead, lesions prevent the acquisition of conditioned sex aversion. These results provide functional evidence for the hypothesis that the ability to make adaptive behavioral alterations is regulated by the IL and PL subregions of the mPFC.

Previous data from our laboratory indicated that mPFC neurons

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      Impulsive behavior decreases from adolescence to adulthood [45–47] possibly reflecting pubertal remodeling of the medial prefrontal cortex (mPFC) as a result of ovarian hormone actions; neurons, glia, and synapses are pruned in female rat mPFC during puberty [48–52]. In fact, female rats with mPFC lesions show less activity during mating [53] and male rats with mPFC lesions are unable to alter maladaptive behaviors during mating [54]. Together, these data suggest that the possible lack of pruning in mPFC in our Prepubertal OVX female rats could account for the greater activity during mating as the impulse to leave after intromissions or mounts may not be suppressed.

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