We recently introduced fluorescent false neurotransmitters (FFNs) as optical tracers that enable the visualization of neurotransmitter release at individual presynaptic terminals. Here, we describe a pH-responsive FFN probe, FFN102, which as a polar dopamine transporter substrate selectively labels dopamine cell bodies and dendrites in ventral midbrain and dopaminergic synaptic terminals in dorsal striatum. FFN102 exhibits greater fluorescence emission in neutral than acidic environments, and thus affords a means to optically measure evoked release of synaptic vesicle content into the extracellular space. Simultaneously, FFN102 allows the measurement of individual synaptic terminal activity by following fluorescence loss upon stimulation. Thus, FFN102 enables not only the identification of dopamine cells and their processes in brain tissue, but also the optical measurement of functional parameters including dopamine transporter activity and dopamine release at the level of individual synapses. As such, the development of FFN102 demonstrates that, by bringing together organic chemistry and neuroscience, molecular entities can be generated that match the endogenous transmitters in selectivity and distribution, allowing for the study of both the microanatomy and functional plasticity of the normal and diseased nervous system. dopamine reporter | secretion kinetics | molecular design | multiphoton imaging D opamine neurotransmission plays a key role in habit learning, motivation, reward, and motor function (1), and altered dopamine neurotransmission is associated with disorders such as Parkinson's disease, schizophrenia, and drug addiction (2-4). As a "social" neurotransmitter that overflows relatively long distances beyond its presynaptic terminals, dopamine's extrasynaptic concentration is principally determined by the combination of exocytotic neurotransmitter release and reuptake by the plasma membrane dopamine transporter (DAT) (5). Psychostimulants, such as cocaine and amphetamine (AMPH), increase extracellular dopamine via interactions with DAT.Extracellular dopamine concentration, particularly in the striatum where it is present at high levels, has been characterized by microdialysis (6, 7) and rapid electrochemical detection using carbon fiber cyclic voltammetry (8, 9) and amperometry (10). The excellent temporal resolution of the electrochemical methods is well suited for measuring changes in extrasynaptic dopamine concentration associated with neuronal activity. However, these approaches usually measure the release and reuptake of dopamine from large sets of striatal dopamine release sites and lack the spatial resolution required to study synaptic transmission at the level of individual presynaptic terminals.Optical methods provide vastly improved spatial resolution so that processes by which specific synapses are modulated can be studied. The first group of fluorescent reporters for the study of presynaptic function were the endocytic FM dyes (11), which act as tracers of exocytosis and endocytosis. Thes...

This study focuses on the role of male-male vocal communication in the reproductive repertoire of the South African clawed frog, . Six male and two female call types were recorded from native ponds in the environs of Cape Town, South Africa. These include all call types previously recorded in the laboratory as well as one previously unidentified male call: chirping. The amount of calling and the number of call types increased as the breeding season progressed. Laboratory recordings indicated that all six male call types were directed to males; three of these were directed to both sexes and three were directed exclusively to males. Both female call types were directed exclusively to males. The predominant call type, in both field and laboratory recordings, was the male advertisement call. Sexual state affected male vocal behaviour. Male pairs in which at least one male was sexually active (gonadotropin injected) produced all call types, whereas pairs of uninjected males rarely called. Some call types were strongly associated with a specific behaviour and others were not. Clasped males always growled and clasping males typically produced amplectant calls or chirps; males not engaged in clasping most frequently advertised. The amount of advertising produced by one male was profoundly affected by the presence of another male. Pairing two sexually active males resulted in suppression of advertisement calling in one; suppression was released when males were isolated after pairing. Vocal dominance was achieved even in the absence of physical contact (clasping). We suggest that males gain a reproductive advantage by competing for advertisement privileges and by vocally suppressing neighbouring males.

No abstract