Independent Differentiation of Sexual and Social Traits

In the process of development in mammals and birds, an individual becomes either male or female. The dogma of sexual differentiation explains this development in terms of gonadal secretions, which direct the growth of an organism along masculine or feminine lines. However, this type of bimodality is not found in all traits that are displayed in reproductive contexts. For example, aggressive behaviors displayed during the breeding season can be expressed by both males and females. Furthermore, this reproductive aggression is highly variable between individuals, regardless of sex. The development of variable traits like reproductive aggression is therefore likely to be influenced by factors in addition to gonadal secretions. We propose that social traits associated with reproduction can differentiate along pathways that are distinct from the developmental pathways of primary sexual traits.     

Nonalgebraic interaction between pressor and depressor reflexes in dogs: evidence for a central site of action

In a previous study (Kendrick, JE and Matson, G 1979, Amer J Physiol 327:H662-H667) we demonstrated that the vascular responses in dogs to electrical stimulation of aortic nerve (AN) pressor and carotid sinus nerve (CSN) depressor afferents did not sum algebraically. We suggest this results from a reflex interaction which occurs in the central nervous system. The present study extends earlier studies by recording sympathetic vasomotor in chloralose-anesthetized dogs. Stimulation of the CSN reduced sympathetic activity by 51 +/- 20 (SD)%. AN stimulation (2 Hz) caused a 17 +/- 12% increase in sympathetic activity. Combined stimulation of the ipsilateral CSN and AN caused 0 +/- 28% change rather than a 34% decrease expected by an additive interaction. The interaction recorded in this study from the sympathetic outflow is therefore consistent with the previously reported vascular responses (cited above) and implicates central nervous site(s) of action. A conditioning stimulus train to CSN inhibited sympathetic discharges to AN test stimuli. This inhibition was prevented by pairing an AN stimulus with the CSN stimulus train. The AN pressor reflexes act in part by increasing sympathetic activity and in part by suppressing the baroreflexes.