Geraldine Katharine Hickey
Advisor: Dr. J. Matthew Kittelberger

The catecholamine neurotransmitters, dopamine and norepinephrine, have been shown to regulate a wide range of social behaviors. However, the mechanisms by which these neurotransmitters modulate social context-dependent actions have not been thoroughly investigated. Here, we look to address this question within the context of vocal behavior in the plainfin midshipman fish (Porichthys notatus). The vocal circuit and behavior of these teleost fish has been well documented. By quantitatively comparing catecholamine distribution in the vocal circuitry of male midshipman, which produce multiple, context-dependent vocalizations, vs. females, with only one vocal response, catecholamine roles in vocal production and modulation can be determined. Male and female brains were stained for tyrosine hydroxylase (TH) in parallel immunohistochemical procedures to localize catecholaminergic neurons. Results were recorded using photomicroscopy and images analyzed using ImageJ software for the presence and intensity of TH staining in male versus female vocal circuitry. Statistically significant staining was seen in the vocal and auditory circuits of both sexes, supporting previous results that one or more catecholamine is involved in vocal production. No differences were seen in staining between males and females in the dorsal posterior nucleus of the thalamus (DP), periaqueductal gray (PAG), and periventricular nucleus of the posterior tuberculum (TPp). However, the proportion of staining in the area ventralis of the telencephalon (V)/pre-optic area (POA), above background levels, between males and females approached the level of statistical significance, with males having more staining than females. Additionally, the proportion of staining in the torus semicircularis was found to be statistically significant between males and females. These results suggest that the V/POA and the TS may be brain areas where sex differences in catecholamine distribution play a role in shaping sexually-divergent vocal behaviors. Future work will use behavioral and physiological studies to investigate the role of specific catecholamines in vocal production and modulation.