Meeting Abstract
P3.74 Saturday, Jan. 5 Physiological and molecular analysis of socially regulated escape behavior NEUMEISTER, H*; HOFMANN, H.A.; PREUSS, T.; Albert Einstein College of Medicine; University of Texas at Austin; Albert Einstein College of Medicine hneumeis@aecom.yu.edu
In the cichlid fish A. burtoni males are brightly colored and territorial (T) or camouflaged and non-territorial (NT). Ts are more vulnerable to predation due to their conspicuous appearance and activity patterns. Do Ts show adaptive physiological changes in the Mauthner cell (M-cell) system that triggers escape (C-starts) in order to maintain escape success? We analyzed C-starts in response to defined sound stimuli using high-speed video and found a higher escape probability in Ts than in NTs (0.58 �0.04 vs. 0.44 �0.05 SEM). Intracellular in vivo M-cell recordings showed that postsynaptic potentials (EPSPs) in response to sound pips are larger in Ts (6.6-8.3 mV) than NTs (2.9-5.8 mV). Also, sensory evoked feedforward inhibition, quantified by the inhibitory shunt in the M-cell soma, was weaker and of shorter duration in Ts. These results suggest that escape threshold is lower in Ts, most likely due to a more excitable M-cell. Serotonin (5-HT) is a likely neuromodulator in this system. We found by immunohistological analysis at least two types of 5-HT fibers in close proximity to the M-cell soma and its two dendrites. We then cloned several 5-HT receptor subtypes and collected the cytoplasm of single M-cells. RT-PCR analysis showed that both the 5A- and 6-receptor subtypes are expressed in M-cells. We suggest that a decrease in 5-HT-controlled inhibitory drive could thus result in a more excitable M-cell in Ts. Indeed, administration of the 5-HT precursor tryptophane decreased escape probability in Ts from 0.52 �0.08 to 0.27 �0.09 SEM, indicating 5-HT modulation in the M-cell system and a low basal 5-HT tone in Ts. Our work provides a novel integrative framework for understanding environmentally mediated neural plasticity at all levels of biological organization.
