Effects of Camphor on Sexual Behaviors in Male Rats

1. Introduction

      Camphor   is   a   ketone   obtained   from Cinnamomum camphora L., or produced synthetically. Camphor is derived from the Arabic word of ‘Kafur’, which means chalk. It has been used for centuries as aphrodisiac, contraceptive, abortificient, cold remedy, antiseptic and suppressor of lactation [1].

    Also it has been widely used as a fragrance in cosmetics, flavoring food additive, scenting agent in a variety of household products, active ingredient in some old drugs, and intermediate in the synthesis of perfume chemicals [2]. Recently, investigations have shown that camphor containing compounds have uterotrophic [3], antitussive [4], anticonvulsant [5], nicotinic receptor blocking [6], antiimplantaion [7], antiestrogenic [8] as well as estrogenic [8-11] activities, and reduced serum triglyceride and thyroid hormone [12].

     In Iran’s folk medicine, camphor has been used both as an aphrodisiac and antiaphrodisi-ac. In small doses, camphor is used as an aphrodisiac to excite the reproductive organs, causing considerable heat in the urethra and nocturnal emissions. However, in large doses, it is used as an antiaphrodisiac to diminish urino-genital irritation. Moreover, it has been suggested to decrease libido and sexual performance [13]. The effects of camphor on sexual performance have never been examined using scientific methods. Therefore, the present study was designed to examine the effects of camphor on sexual behaviors in adult male rats.

2. Chemicals and Methods

2.1. Chemicals

     Camphor was purchased form Kimya Mavad Chemical Company, estradiol valerate and progesterone from Abooryhan pharmaceutical company, olive oil from Levieh company, ethanol and diethyl ether form May & Baker LTD, Dagenham, England.

2.2. Animals

    Adult Sprague-Dawley rats (50-60 day-old) of both sexes were obtained from Razi Institute, Shiraz, Iran, and were housed in a temperature (19-23 °C) and light-controlled (12 h light/12 h dark) condition, with access to rat chaw and tap water ad libitum.

2.3. Experimental design and protocol

     Twenty four male rats were equally assigned to a control and three treatment groups. The control group received daily i.p. injections of the vehicle (olive oil; 2.5 ml/kg) for 7 days. Treatment groups received camphor in olive oil at 2.5, 12.5 or 50 mg/kg, respectively. Twenty four female rats were also used to study sexual behavior of male rats. They were brought to sexual receptiveness by intramuscular injections of estradiol valerate (0.1 mg/rat) and progesterone (1 mg/rat) at 72 and 3 h before behavioral recording, respectively [14].

     Twenty four h after administration of the last dose of vehicle or camphor, sexual behaviors were studied in an isolated room. Five minutes after the placement of male rats in a Plexiglas container, female rats were introduced. Afterwards, mount latency (ML), mount frequency (MF), intromission latency (IL) and intromission frequency (IF) were recorded for 15 min. to assess sexual behaviors. ML was the latency in seconds from the introduction of a female rat to the first mount by a male; MF was the number of mounts by a male rat without intromission within a series; IL was the latency in seconds from the introduction of a female rat to the first intromission, and IF was the number of intromissions in a series [14].

2.5. Statistical analysis

      The data, presented as mean ±SEM, were analyzed using one-way analysis of variance (ANOVA). Where a significant difference was detected by ANOVA, the treated groups were compared with the control one using Dunnett test. A probability of committing type one error was set at a  p < 0.05.

3. Results

      There was no significant difference in MF or IF from rats treated with olive oil and those treated with camphor at doses of 2.5, 12.5 or 50 mg/kg (Figures 2 and 4). However, the ML and IL of groups received camphor at 50 mg/kg were significantly different from those of the control group (Figures 1 and 3).

Figure1. Mount latency (mean±SEM) from the olive oil (vehicle) and camphor-treated groups (n=6 each) after receiving daily i.p. injections of olive oil (2.5 ml/kg) or camphor (2.5, 12.5 or 50 mg/kg) for 7 days. * Significantly (p < 0.05) difference from olive oil-treated group.

Figure 2. Mount frequency (mean±SEM) from the olive oil (vehicle) and camphor-treated groups (n=6 each) after receiving daily intraperitoneal injections of olive oil (2.5 ml/kg) or camphor (2.5, 12.5 or 50 mg/kg) for 7 days

Figure 3. Intromission latency (mean±SEM) from the olive oil (vehicle) and camphor-treated groups (n=6 each) after receiving daily intraperitoneal injections of olive oil (2.5 ml/kg) or camphor (2.5, 12.5 or 50 mg/kg) for 7 days.

Figure 4. Intromission frequency (mean±SEM) from the olive oil (vehicle) and camphor-treated groups (n=6 each) after receiving daily intraperitoneal injections of olive oil (2.5 ml/kg) or camphor (2.5, 12.5 or 50 mg/kg) for 7 days.

4. Discussion and conclusion

     Camphor is sometimes mixed into the Betel quid for its stimulating and aphrodisiac properties. However, whether camphor acts as an aphrodisiac or antanaphrodisiac seems to be a matter of dosage. Islamic sects and certain Buddhist groups use the incense to ‘cool off’ any Venusian drives, while Tantric sects value it for its stimulating effect. Medicinally, camphor has a long established history, not just in the Far East, but also in Europe. In Ayurvedic medicine, it is used to increase prana, open the senses and to clear the mind. It is said to cool the nerves in cases of hysteria [15].

     One of the methods for assessing male reproductive capacity in human is the evaluation of reproductive history and behavior parameters including sexual desire, motivation, performance and satisfaction [16]. In the rat model of sexual behavior ML, MF and IL can be considered as measures of sexual desire and motivation and IF and IL as measures of performance [17].

     The findings of the present study showed that there were no significant differences in MF and IF from the control and camphor-treated groups. However, there were significant decreases in ML and IL in rats received camphor at a dose of 50 mg/kg compared to that of the control group. The reduction of ML indicates that camphor enhanced sexual desire and motivation, and the reduction of IL is suggestive of enhanced sexual performance.

      The enhancement of sexual desire by camphor might be mediated through the increase of the synthesis of testosterone in male rats. The peak of plasma testosterone levels in the rat occurs around 50-60 days of age [18]. Therefore, rats with such an age range were employed in the present study. There is a large body of animal data documenting hormonal regulation of male sexual behavior and the neural site of action of these hormones [16]. Libido and male behavior are probably mediated by testosterone receptors in the CNS [19]. It would be interesting to examine the effects of camphor on serum levels of testosterone, and to study as to whether or not it is correlated with the sexual performance.

     The effects of camphor on sexual performance might also be mediated via its effects on sympathetic nervous system, since an earlier report showed that camphor specifically inhibited catecholamine secretion by blocking nicotinic acetylcholine receptors [6]. Libido is under psychosomatic, neurogenic, vascular and hormonal (primarily testosterone) controls [19]. Considerable recent evidence indicates that drugs which alter brain monoamine levels also affect copulatory behavior in male rats. Moreover, it is believed that copulatory behavior may be regulated in part by a balance between serotonergic and noradrenergic tone [14]. The role of sympathetic and parasympathetic systems in male sexual behavior as well as the ability of camphor to inhibit catecholamine secretion might suggest that the effects of camphor on sexual behavior might be mediated through modulation of sympathetic nervous system.