Related Experiment Video
Updated: Jul 19, 2026
05:17
Swimming Exercise Protocol and Care Methods for Pregnant Rats
Published on: April 5, 2024
Sexual dimorphism in hybrids rats.
Alicia Garcia-Falgueras1, Helena Pinos, Rosa Fernández
1Departamento de Psicobiologia, UNED C/ Juan del Rosal 10, 28040 Madrid, Madrid, Spain.
Brain Research
|October 31, 2006
Summary
Brain sex differences in the medial posterior bed nucleus of the stria terminalis (BSTMP) are stable across rat generations. However, neuronal counts in the locus coeruleus (LC) and medial anterior bed nucleus of the stria terminalis (BSTMA) vary.
Area of Science:
- Neuroscience
- Behavioral Genetics
- Comparative Anatomy
Background:
- Laboratory rat strains originate from Wistar rats through artificial selection.
- Previous studies identified sexual dimorphism in the BSTMP of Wistar and Long-Evans rats, but not in BSTMA or LC of Long-Evans.
- BSTLP was found to be isomorphic in both strains.
Purpose of the Study:
- To investigate neuronal counts in BSTMP, BSTMA, BSTLP, and LC across generations of Wistar and Long-Evans rats and their hybrids.
- To determine the inheritance patterns of sexual dimorphism in these brain regions.
- To explore the mechanisms underlying neuronal number regulation versus sex ratio stability.
Main Methods:
- Studied neuronal numbers in the BSTMP, BSTMA, BSTLP, and LC of male and female Wistar and Long-Evans rats (F(0)).
- Analyzed neuronal counts in the F(1) and F(2) hybrid generations derived from these crosses.
- Compared sexual dimorphism and neuronal number changes across generations and between strains.
Main Results:
- Sexual dimorphism in BSTMP persisted across F(0), F(1), and F(2) generations.
- Sex differences in LC were limited to F(0) Wistar rats, disappearing in Long-Evans and hybrids.
- Sex differences in BSTMA were present in F(0) Wistar but absent in Long-Evans and F(2) hybrids.
- LC neuronal numbers decreased in F(1) and increased in F(2) generations.
- BSTMP neuronal numbers changed significantly across generations, but the female/male ratio remained stable.
- The regulation of neuronal number differs from the regulation of the female/male ratio.
Conclusions:
- BSTMP sexual dimorphism is a robust trait, unaffected by heterozygosis or homozygosis, suggesting a conserved 'fixed' brain sex difference in mammals.
- Mechanisms controlling neuronal number and the female/male ratio in brain regions are distinct.
- Genetic factors influencing sexual dimorphism in BSTMA and LC are subject to segregation and recombination in hybrid generations.
Related Concept Videos
02:45The Ratio of X Chromosome to Autosomes
In most organisms, sex is determined by the ratio of X and Y chromosomes. However, in some organisms, such as Drosophila and C.elegans, sex is determined by the ratio of the number of X chromosomes to the number of sets of autosomes. The Y chromosome in Drosophila is active but does not determine sex. It contains genes responsible for the production of sperms in adult flies.
Normal male Drosophila has a ratio of one X chromosome to two sets of autosomes. In contrast, normal female Drosophila...
Normal male Drosophila has a ratio of one X chromosome to two sets of autosomes. In contrast, normal female Drosophila...
01:17Understanding Species and Reproductive Barriers
A species is a group of organisms that interbreed and produce fertile offspring. Typically, individuals of the same species appear similar and share common characteristics due to their highly similar genomes. However, not all organisms that look alike are members of the same species. Various mechanisms keep most species discrete. While some mechanisms prevent reproductive behavior and fertilization (pre-zygotic isolation), others prevent the production of fertile offspring after mating has...
02:29Hybrid Zones
Hybrid zones are narrow regions where two closely related species interact, mate, and produce hybrids. Relative to either parent species, hybrids may possess distinct phenotypic or genetic differences that impact their survival and reproductive success. The genetic variances introduced by hybridization influence species diversity and speciation processes within the hybrid zone.Gene flow and natural selection are evolutionary mechanisms that shape the outcome of a hybrid zone. Gene flow...