Behavioral and physiological responses to central administration of corticotropin-releasing factor in the bluebanded goby (Lythrypnus dalli)

Abstract

Central manipulation of neuromodulators is critical to establishing causal links between brain function and behavioral output. The absence of a rigorous method of evaluating intracerebroventricular (icv) injection efficacy in small model organisms is one reason why peripheral administration of neuroactive substances is more common. We use the bluebanded goby (Lythrypnus dalli), a small, highly social fish, to 1) validate our method of icv injection by testing the hypothesis that corticotropin-releasing factor (CRF) elevates ventilation rate (VR) and 2) propose a novel bioassay using basal physiology and behavior during recovery from anesthesia/icv administration to assess injection efficacy, neuromodulator activity, and procedural confounds. Central CRF administration significantly increased ventilation rate, demonstrating successful delivery of CRF to the brain. There were no significant differences in cortisol among treatments. The injection procedure did, however, decouple the temporal relationship between the initiation of ventilation and time to regain equilibrium present in control fish. Importantly, neither icv vehicle nor CRF injection affected the initiation of ventilation, disrupted the stereotyped recovery pattern following anesthesia, or initiated an endocrine stress response. Taken together, we suggest that 1) icv injection can be effectively used to manipulate central levels of CRF in L. dalli and 2) physiological and behavioral recovery from anesthesia may be used to evaluate injection/technique efficacy. We will use these data in future studies as a measure of effective CRF delivery, to allow for appropriate recovery from icv injection, and to better evaluate independent effects of CRF on social and/or sexual behavior.