Meeting Abstract
Gonadotropin-releasing hormone (GnRH) 1 neurons in the hypothalamus regulate the reproductive axis, whereas GnRH2 and GnRH3 have widespread projections throughout the brain in most vertebrates. These extra-hypothalamic GnRH neurons are neuromodulators that integrate sensory information important for mediating behaviors. However, little is known about whether this modulatory potential in specific sensory processing regions of the brain might be influenced by an animal’s reproductive condition. The cichlid fish Astatotilapia burtoni is an ideal model to examine GnRH modulation of sensory function because courting males produce visual-acoustic courtship displays towards gravid receptive females, but non-receptive mouthbrooding females are typically uninterested in male signals. Immunostaining demonstrates dense innervation of GnRH2/3 to visual-acoustic processing centers in the midbrain; tectum and torus semicircularis. To test for reproductive state-dependent changes in GnRH modulatory potential, we analyzed mRNA levels of GnRH receptors in microdissections of these midbrain regions in gravid, recovering, and mouthbrooding females. In the tectum, GnRH-R2 levels were higher in mouthbrooding compared to gravid and recovering females. In the torus semicicularis, however, GnRH-R2 levels were higher in gravid compared to mouthbrooding females. We are currently analyzing GnRH 2/3 innervation to these nuclei by quantifying varicosity densities across reproductive states. These results demonstrate reproductive-state changes in the neural substrates associated with GnRH 2/3 modulation and contribute to better understanding the mechanisms responsible for sensory plasticity that leads to adaptive behaviors.
