Cross-sex HT induces sex-specific changes in android, gynoid regions
Sex differences in aggression: Differential roles of 5-HT2, neuropeptide F and tachykinin
Few studies have examined the relationship between genetics, stress, and sex-linked differences in neurotransmitter systems. Examining serotonin 5-HT receptor knockout mice on stress-induced behavioral depression, female 5-HT1B receptor knockout mice demonstrated significantly reduced immobility than either male 5-HT1B receptor knockout mice or male and female wild-type mice on the tail suspension test TST and forced swimming test. The behavioral phenotype was identified as likely due to a disinhibition of 5-HT release, because depletion of 5-HT with parachlorophenylalanine selectively reduced immobility of female 5-HT1B receptor knockout mice in the TST. In contrast, male and female 5-HT1A receptor knockout mice demonstrated reduced immobility compared with control mice, but the depletion of 5-HT with PCPA did not reverse the antidepressant-like phenotype. Microdialysis studies confirmed significantly higher baseline levels of hippocampal 5-HT in female, but not male, 5-HT1B receptor knockout mice.
Numerous examples in medicine illustrate that different rates of illness between men and women based on biologic differences usually reflect important aspects of the underlying pathophysiology. This can be important for psychiatry, since several psychiatric illnesses have large sex differences in incidence rates. However, after nearly half a century of increasingly sophisticated research on the biologic basis of these illnesses, we still do not have a clear picture of the specific biochemical events that lead to symptom formation in patients. The paper by Nishizawa et al. Since the advent of modern neuropharmacologic research in the s, the brain 5-HT system has been a major focus of intense investigation.
However, critical gaps exist in our knowledge of invertebrates that need to be addressed before definitively stating opposing roles for 5-HT and aggression. Specifically, the role of 5-HT receptor subtypes are largely unknown, as is the potential interactive role of 5-HT with other neurochemical systems known to play a critical role in aggression. Similarly, the influence of these systems in driving sex differences in aggressive behavior of invertebrates is not well understood. Here, we investigated these questions by employing complementary approaches in a novel invertebrate model of aggression, the stalk-eyed fly. A combination of altered social conditions, pharmacological manipulation and 5-HT 2 receptor knockdown by siRNA revealed an inhibitory role of this receptor subtype on aggression.