Meeting Abstract

P3.123  Wednesday, Jan. 6  Differential regulation of mRNAs encoding vasotocin and its receptors in the teleost hypothalamus following acute stress LEMA, S.C.; Univ. of North Carolina, Wilmington lemas@uncw.edu

The nonapeptide hormones vasotocin/vasopressin (AVT/AVP) have been implicated in several vertebrate taxa as regulators of the HPA axis. In fish, AVT/AVP synergize with corticotropin-releasing hormone to stimulate secretion of adenocorticotropic hormone (ACTH). Accordingly, hypothalamic pro-AVT mRNA expression has been shown to be regulated by stress in fishes. Recently, multiple receptors for AVT – two distinct receptor paralogs (V1a1 and V1a2) in the mammalian V1a-type receptor family and a single V2-type receptor – were identified in the teleost Cyprinodon nevadensis amargosae, the Amargosa pupfish. It remains unclear, however, which of these receptors are involved in AVT regulation of the physiological stress response. In this study, quantitative real-time PCR was used to examine changes in mRNAs encoding pro-AVT and its receptors in the hypothalamus of sexually-mature Amarogsa pupfish following acute capture stress. Hypothalamic pro-AVT mRNA levels increased 1.8-fold in both male and female pupfish over a 2 hr period following capture stress. In males, transcripts for the V1a1 and V1a2 receptors declined up to 50% within 40 min of capture from pre-stress baseline levels. In females, however, hypothalamic V1a1 mRNA levels were briefly elevated at 40 min following capture only to decline below baseline levels at 80 min and 120 min after capture, while transcripts for the V1a2 receptor were unaltered. Transcript abundance for the V2 receptor was not affected by acute capture stress in the hypothalamus of either sex. Taken together, these findings indicate sex differences in hypothalamic V1a1 and V1a2 mRNA regulation following acute stress, and suggest that these V1a-type receptors might mediate AVT’s influences on how fish respond physiologically and behaviorally to stress.