Lema S C, Sanders K E, Walti K A
Biological Sciences Department, Center for Coastal Marine Sciences, California Polytechnic State University, San Luis Obispo, CA, USA.
J Neuroendocrinol. 2015 Feb;27(2):142-57. doi: 10.1111/jne.12239.
Nonapeptide hormones of the vasopressin/oxytocin family regulate social behaviours. In mammals and birds, variation in behaviour also is linked to expression patterns of the V1a-type receptor and the oxytocin/mesotocin receptor in the brain. Genome duplications, however, expand the diversity of nonapeptide receptors in actinopterygian fishes, and two distinct V1a-type receptors (v1a1 and v1a2) for vasotocin, as well as at least two V2-type receptors (v2a and v2b), have been identified in these taxa. The present study investigates how aggression connected to social status relates to the abundance patterns of gene transcripts encoding four vasotocin receptors, an isotocin receptor (itr), pro-vasotocin (proVT) and pro-isotocin (proIT) in the brain of the pupfish Cyprinodon nevadensis amargosae. Sexually-mature pupfish were maintained in mixed-sex social groups and assessed for individual variation in aggressive behaviours. Males in these groups behaved more aggressively than females, and larger fish exhibited higher aggression relative to smaller fish of the same sex. Hypothalamic proVT transcript abundance was elevated in dominant males compared to subordinate males, and correlated positively with individual variation in aggression in both social classes. Transcripts encoding vasotocin receptor v1a1 were at higher levels in the telencephalon and hypothalamus of socially subordinate males than dominant males. Dominant males exhibited elevated hypothalamic v1a2 receptor transcript abundance relative to subordinate males and females, and telencephalic v1a2 mRNA abundance in dominant males was also associated positively with individual aggressiveness. Transcripts in the telencephalon encoding itr were elevated in females relative to males, and both telencephalic proIT and hypothalamic itr transcript abundance varied with female social status. Taken together, these data link hypothalamic proVT expression to aggression and implicate forebrain expression of the V1a-type receptor v1a2 as potentially mediating the effects of vasotocin on behaviour in male fish. These findings also illustrate how associations between social status, aggression and gene expression within the VT and IT nonapeptide systems can be contingent on behavioural context.
血管加压素/催产素家族的九肽激素调节社会行为。在哺乳动物和鸟类中，行为的变化也与大脑中V1a型受体和催产素/中催产素受体的表达模式有关。然而，基因组复制增加了辐鳍鱼类中九肽受体的多样性，并且在这些分类群中已鉴定出两种不同的血管紧张素原受体（v1a1和v1a2）以及至少两种V2型受体（v2a和v2b）。本研究调查了与社会地位相关的攻击性如何与内华达鳉（Cyprinodon nevadensis amargosae）幼鱼大脑中编码四种血管紧张素原受体、一种异催产素受体（itr）、血管紧张素原（proVT）和异血管紧张素原（proIT）的基因转录本的丰度模式相关。将性成熟的内华达鳉饲养在混合性别的社会群体中，并评估其攻击行为的个体差异。这些群体中的雄性比雌性表现得更具攻击性，并且相对于同性别的小鱼，体型较大的鱼表现出更高的攻击性。与从属雄性相比，优势雄性下丘脑proVT转录本丰度升高，并且在两个社会阶层中均与攻击行为的个体差异呈正相关。在社会从属雄性的端脑和下丘脑中，编码血管紧张素原受体v1a1的转录本水平高于优势雄性。相对于从属雄性和雌性而言，优势雄性下丘脑v1a2受体转录本丰度升高，并且优势雄性端脑中v1a2 mRNA丰度也与个体攻击性呈正相关。相对于雄性，雌性端脑中编码itr的转录本升高，并且端脑proIT和下丘脑itr转录本丰度均随雌性社会地位而变化。综上所述，这些数据将下丘脑proVT表达与攻击性联系起来，并表明V1a型受体v1a2的前脑表达可能介导血管紧张素原对雄鱼行为的影响。这些发现还说明了社会地位、攻击性与VT和IT九肽系统内基因表达之间的关联如何可能取决于行为背景。
