Effects of alcohol on the sexual motivation of the male rat

doi:10.1016/0091-3057(94)90202-X

Pharmacology Biochemistry and Behavior

Volume 48, Issue 4, August 1994, Pages 929-934

https://doi.org/10.1016/0091-3057(94)90202-X Get rights and content

Abstract

Previous research measuring the effects of alcohol on sexual behavior has primarily focused on its effects on copulation. The present experiment was designed to investigate the effects of alcohol on the sexual motivation of the male rat by requiring operant responding to gain access to a sexually receptive female. A novel apparatus was used that allowed both visual and olfactory cues from an estrous female to reach the male. Lever presses resulted in the opening of a door that permitted the male rat to enter an adjacent chamber where a receptive female was located. Treatment with low to moderate doses of alcohol (0.5 g/kg and 1.0 g/kg) resulted in increased latencies to emit the first response of the males working for access to females, but did not affect response rate or subsequent mount or ejaculation latencies, when these males were allowed access to the receptive female. Furthermore, alcohol failed to show any response-reinstating or disinhibitory effects when tested following a period of nonreinforced extinction trials. An additional experiment, in which rats received equivalent doses of alcohol, revealed no decrease in spontaneous locomotion. Taken together, these data suggest that the response-reducing effects of alcohol are probably not a result of general drug-induced reductions in activity, but rather an attenuating action of the drug on sexual motivation.

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Moreover, Ferraro and Kiefer (2004) reported a significant increase in activity (level changing) before the arrival of a sexually receptive female in rats receiving ethanol compared to controls. In contrast, another study found that rats receiving comparable amounts of ethanol were less likely to press a bar for access to a sexually receptive female, suggesting suppressive effects of ethanol on sexual motivation (Scott, Ettenberg, & Olster, 1994). Surprisingly, in the present study, adult rats showed high levels of preference for receptive females after forced consumption of ethanol, and no differences in behavior were seen after abstinence.
Adolescence is a sensitive period of brain development when changes in hormone levels may have long-lasting effects on synaptic connections and behavior. In humans, alcohol consumption frequently begins during this critical period, although the impact of early exposure has not been fully examined. The current study was designed to investigate short- and long-term effects of repeated forced ethanol consumption during adolescence on emerging reproductive behaviors. Twenty-six young male Long-Evans rats were assigned to ethanol (Young EtOH, n = 12) or water (Young Control, n = 14) groups at postnatal day (P) 32, receiving a modified binge protocol of 3 g/kg of solution via gavage twice per week from P32 to P80. For comparison, another cohort of rats received a similar treatment paradigm in adulthood from P75–P133 (Adult EtOH, n = 8; Adult Control, n = 10). Reproductive behavior was assessed with tests for copulation, partner preference, and 50-kHz vocalizations during forced consumption (intoxication) and again after a 4–5 week period of abstinence. During forced consumption, the Young EtOH group showed significantly longer latencies on copulation tests than Young Controls, but these differences did not persist after abstinence. Different patterns were observed in Adult animals, who only showed significant, delayed impairments in the post-ejaculatory interval. Preference for sexually receptive females increased with sexual experience in both adolescent and adult rats, regardless of treatment during the forced consumption phase. However, after abstinence, the Young EtOH group showed a significantly reduced partner preference compared to the Young Control group, which may indicate long-term effects on sexual motivation. Additionally, during forced consumption the Young EtOH group tended to emit fewer ultrasonic vocalizations, perhaps reflecting impairments in sexual communication. Adult groups showed no differences in partner preference or vocalization tests at any time. Taken together, these findings indicate that repeated, intermittent ethanol exposure may have moderate effects on reproductive behavior that vary as a function of age. After abstinence, differences were only observed in the younger group, suggesting that the adolescent brain and behavior are more sensitive to ethanol exposure than the adult brain for sexual motivation and performance.
Anabolic-androgenic steroids and appetitive sexual behavior in male rats
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Once operant responding stabilized at FI10, there was no difference in response rates between vehicle- (30.6 ± 4.3 responses/10 min) and testosterone-treated rats (28.1 ± 4.4, p > 0.05). Overall operant responding for food reward on an FI10 schedule was similar to that reported previously (Scott et al., 1994). Although initial body weights were not different, body weight in testosterone-treated rats was significantly lower at the end of the study (553.3 ± 10.0 g vs 612.5 ± 23.0 g in vehicle controls, p < 0.05, d = 1.6), as reported previously (Wood et al., 2013).
Anabolic–androgenic steroids (AAS) increase libido and sexual behavior, but the underlying behavioral mechanisms are unclear. One way AAS may enhance expression of sexual behavior is by increasing the willingness to work for sex. In the present study, sexually-experienced male rats received daily injections of testosterone at supraphysiologic doses (7.5 mg/kg in water with 13% cyclodextrin) or vehicle and were tested for appetitive sexual behavior measured by operant responding for access to an estrous female. Initially, rats were trained in their home cage to respond on a nose-poke under a 10-min fixed-interval schedule for food reward. Once rats achieved stable response rates, the food was replaced by a female, followed by mating for 10 min. There was no effect of testosterone on operant responding for food (28.1 ± 4.4 responses/10 min for testosterone, 30.6 ± 4.3 for vehicle) or sex (35.0 ± 4.0 responses/10 min for testosterone, 37.3 ± 5.2 for vehicle). However, rats made significantly more responses for sex than for food (p < 0.05), and responses for food and sex were positively correlated among individuals (R² = 0.6). Additional groups of rats were trained to respond on a lever for the female under a 2nd-order schedule of reinforcement, where 5 responses opened a door to show the female for 5 s. After 15 door openings, the male gained access to the female. There was no effect of testosterone on time to complete 75 responses: 38.4 ± 7.8 min for vehicle controls vs 43.3 ± 6.6 min for testosterone-treated rats (p > 0.05). These findings suggest that chronic high-dose testosterone does not enhance appetitive drive for sexual behavior.
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The use of addictive drugs can have profound short- and long-term consequences on social behaviors. Similarly, social experiences and the presence or absence of social attachments during early development and throughout life can greatly influence drug intake and the susceptibility to drug abuse. The following review details this reciprocal interaction, focusing on common drugs of abuse (e.g., psychostimulants, opiates, alcohol and nicotine) and social behaviors (e.g., maternal, sexual, play, aggressive and bonding behaviors). The neural mechanisms underlying this interaction are discussed, with a particular emphasis on the involvement of the mesocorticolimbic dopamine system.
Inhibitory and disinhibitory effects of psychomotor stimulants and depressants on the sexual behavior of male and female rats
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Drugs of abuse comprise several pharmacological classes, including psychomotor stimulants, such as amphetamine and cocaine, and CNS depressants, such as morphine and alcohol. Few studies have examined the effects of those drugs systematically on human sexual behavior, although substantial clinical and epidemiological literatures suggest that drugs in both classes either inhibit sexual responding or can be “prosexual” in certain situations, thereby increasing the potential of risky sexual activity and the spread of sexually transmitted diseases. This paper reviews original data in rats showing that both classes of drug inhibit or disinhibit sexual behavior depending on the animal's baseline level of sexual responding, hormonal status, whether the drug is given acutely or chronically, and whether the animal has learned to inhibit sexual responding toward nonreceptive partners or in the presence of conditioned olfactory cues that predict sexual nonreward.
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We are interested in developing animal models to evaluate cognitive processes as influenced by the interplay of steroidal hormones and drugs commonly used in psychotherapy. Two experiments with female rats were conducted to evaluate the interaction of estrogen with the serotonin specific reuptake inhibitor (SSRI) fluoxetine on spatial learning and memory and on the endocrine system. In experiment 1, estrogen (50 μg estradiol benzoate/kg body weight) was administered SC to young adult, ovariectomized (OVX) rats either alone or in combination with fluoxetine (2 mg/kg SC). After a month, the groups were compared with appropriate OVX and gonadally intact controls on trials to criterion in a hole board spatial memory task using massed training trials. Experiment 2 was a dose–response study of the influence of fluoxetine (0.5–5 mg/kg) on circulating estrogen in OVX, estrogen treated females. Results were that the OVX females administered estrogen only reached the learning criterion significantly faster than the other groups. All other groups, including the estrogen+fluoxetine animals, performed no better than the controls. Combining fluoxetine with estrogen also lowered circulating estrogen titers, with the least estrogen reductions being in the group receiving the highest dosage of fluoxetine. No differences among groups were found on measures of activity in an open field or for anxiety in a plus maze. Conclusions were that administration of estrogen improved spatial learning and memory in OVX rats, whereas concurrent fluoxetine exposure suppressed the levels of estrogen in circulation and eliminated the gains in spatial performance obtained from chronic estrogen exposure.
Behavioral analysis of male rat sexual motivation and performance following acute ethanol treatment
2004, Pharmacology Biochemistry and Behavior
To characterize the effects of acute ethanol treatment on sexual motivation and performance, 30 male Long–Evans rats were assigned to one of three treatment conditions: saline (n=9), 0.25 g/kg ethanol (n=10), or 1.0 g/kg ethanol (n=11). Males were injected intraperitoneally 30 min before behavioral testing. Male rats were placed in a multilevel testing chamber 5 min prior to the introduction of a receptive female rat and level changes were recorded as an index of sexual motivation. After the female rat was placed in the chamber, standard measures of sexual performance were recorded over three weekly tests. Results indicated that the highest dose of ethanol (1.0 g/kg) increased male rat level-changing behavior compared to the saline group. Although ethanol treatment failed to affect most measures of sexual performance, males administered 1.0 g/kg ethanol had fewer anogenital investigations and had longer postejaculatory intervals (PEIs) compared to control animals. The data from this experiment suggest that ethanol increases rodent sexual motivation but impairs specific parameters of sexual performance.

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Effects of alcohol on the sexual motivation of the male rat

Abstract

Alcohol

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Neuroscience

Alcohol

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Effects of alcohol ingestion on copulatory behavior of male rats

Psychopharmacologia