Ivermectin impairs sexual behavior in sexually naive, but not sexually experienced male rats

Ivermectin (IVM) is an antiparasitic drug, widely used in domestic animals. In mammals, IVM act as a GABA agonist. This neurotransmitter has an important role in the regulation of sexual behavior. Thus, this study sought to investigate the effects of various medically relevant doses IVM on the sexual behavior of male rats. In particular, we also wished to examine if previous sexual experience modulated responses to IVM. In the first experiment, the sexual behavior of inexperienced male rats was analyzed after they received 0.2, 0.6, 1.0 or 2.0 mg/kg IVM, 15 mm prior to behavioral testing. In the second experiment, the effects of four previous sexual experiences on IVM treated rats (1.0 or 2.0 mg/kg, 15 min prior to the 5th session) were assessed. The standard therapeutic dose (0.2 mg/kg) did not impair the sexual behavior of inexperienced male rats. At a more concentrated dose (0.6 mg/kg), which is still within the therapeutic range, the appetitive phase of sexual behavior of inexperienced male rats was impaired. Likewise, 1.0 mg/kg impaired the appetitive phase. Previous sexual experience blocked almost entirely this sexual impairment, suggesting that previous sexual experience exerts a positive effect in attenuating the sexual impairment produced by IVM treatment. Therefore, the standard therapeutic dose of IVM can be used without producing side effects on sexual behavior. Use of more concentrated therapeutic doses is not recommended during reproductive periods, unless the animals have had previous sexual experience. (C) 2010 Elsevier Ltd. All rights reserved.

Moxidectin interference on sexual behavior, penile erection and hypothalamic GABA levels of male rats

The moxidectin (MXD) is an antiparasitic drug used in domestic animals. The mechanism of action, in mammals, involves GABA, a neurotransmitter with an important role in the sexual behavior control. Presently, the effects of 0.2 mg/kg therapeutic dose were studied on sexual behavior, sexual motivation, penile erection and central GABA levels. Sexual behavior results showed increased latencies to the first mount and intromission as well as in inter-intromission interval; a reduction in total mounts was detected on the drug post-treatment. No difference was observed between sexual motivation of control and experimental animals. MXD treatment reduced penile erection and hypothalamic GABA levels. The results suggest that MXD reduced sexual behavior and penile erection by an action on the hypothalamic GABA system. Probably, the lack of effects in the motivational test and the increased mount and intromission latencies as well as decreased total mounts could be explained as a consequence of reduced male rat erection process. (C) 2007 Elsevier Ltd. All rights reserved.

Sexual recombination in Phytophthora cinnamomi in vitro and aggressiveness of single-oospore progeny to Eucalyptus

Fifty single oospore progeny were established from an in vitro mating of A1 and A2 mating type isolates of Phytophthora cinnamomi from South Africa. Forty-nine progeny were identified as F-1 hybrids using seven random amplified polymorphic DNA (RAPD) primers, and one was a selfed isolate of the A1 mating type parent. Among the hybrid progeny, 24 and 25 were A1 and A2 mating type, respectively. Aggressiveness of progeny and parental isolates was assessed on 1-year-old seedlings of Eucalyptus smithii. The mean aggressiveness of hybrid oosporic isolates, expressed as lesion length, was significantly (P = 0.0001) lower than that of the parental isolates. No significant difference in aggressiveness of A1 and A2 mating type F-1 hybrid isolates was observed. This is the first report demonstrating sexual recombination in vitro in P. cinnamomi.

Regulation of male sexual development by Sry and Sox9

Sry, a gene from the Y chromosome, is known to initiate testis formation and subsequent male differentiation in mammals. A related gene, Sox9, also plays a critical role in testis determination, possibly in all vertebrates. A number of models have been presented regarding the molecular modes of action of these two genes. However, details regarding their regulation, regulatory target genes, and interacting protein factors and co-factors have not been established with any certainty. In this review, we examine new evidence and re-examine existing evidence bearing on these issues, in an effort to build up an integrative model of the network of gene activity centred around Sry and Sox9. J. Exp. Zool. 290:463-474, 2001. (C) 2001 Wiley-Liss, Inc.

Interaction between natural and sexual selection during the evolution of mate recognition

The interaction between natural and sexual selection is central to many theories of how mate choice and reproductive isolation evolve, but their joint effect on the evolution of mate recognition has not, to my knowledge, been investigated in an evolutionary experiment. Natural and sexual selection were manipulated in interspecific hybrid populations of Drosophila to determine their effects on the evolution of a mate recognition system comprised of cuticular hydrocarbons (CHCs). The effect of natural selection in isolation indicated that CHCs were costly for males and females to produce. The effect of sexual selection in isolation indicated that females preferred males with a particular CHC composition. However, the interaction between natural and sexual selection had a greater effect on the evolution of the mate recognition system than either process in isolation. When natural and sexual selection were permitted to operate in combination, male CHCs became exaggerated to a greater extent than in the presence of sexual selection alone, and female CHCs evolved against the direction of natural selection. This experiment demonstrated that the interaction between natural and sexual selection is critical in determining the direction and magnitude of the evolutionary response of the mate recognition system.

Species richness in agamid lizards: chance, body size, sexual selection or ecology?

Why does species richness vary so greatly across lineages? Traditionally, variation in species richness has been attributed to deterministic processes, although it is equally plausible that it may result from purely stochastic processes. We show that, based on the best available phylogenetic hypothesis, the pattern of cladogenesis among agamid lizards is not consistent with a random model, with some lineages having more species, and others fewer species, than expected by chance. We then use phylogenetic comparative methods to test six types of deterministic explanation for variation in species richness: body size, life history, sexual selection, ecological generalism, range size and latitude. Of eight variables we tested, only sexual size dimorphism and sexual dichromatism predicted species richness. Increases in species richness are associated with increases in sexual dichromatism but reductions in sexual size dimorphism. Consistent with recent comparative studies, we find no evidence that species richness is associated with small body size or high fecundity. Equally, we find no evidence that species richness covaries with ecological generalism, latitude or range size.