Tyramine as an independent transmitter and a precursor of octopamine in the locust central nervous system: An immunocytochemical study

Abstract

Octopamine and its precursor tyramine are biogenic amines that are found ubiquitously in insects, playing independent but opposite neuromodulatory roles in a wide spectrum of behaviors, ranging from locomotion and aggression to learning and memory. We used recently available antibodies to octopamine and tyramine to label the distribution of immunoreactive profiles in the brain and ventral nerve cord of the locust. In the brain and all ventral cord ganglia all known octopaminergic neurons were labeled with both the tyramine and octopamine antisera. In the brain the subesophageal ganglion and all fused abdominal ganglia we found somata that were only labeled by the tyramine antibody. Some prominent architectural features of the brain, like the protocerebral bridge, the central body, and associated neuropils, also contain intensely labeled tyramine-immunoreactive fibers. In addition, tyraminergic fibers occur in all ganglia of the ventral cord. For known octopaminergic neurons of the thoracic ganglia, octopamine-immunoreactivity was confined to the cell body and to the varicosities or boutons, whereas fiber processes always expressed tyramine-immunoreactivity. The distribution of the tyramine and octopamine content within these neurons turned out to be dependent on how the animal was handled before fixation for immunocytochemistry. We conclude that tyramine is an independent transmitter in locusts, and that in octopaminergic neurons the ratio between octopamine and its precursor tyramine is highly dynamic.

Trace Amines and Their Receptors

“…TYR and OCT are now well established signaling molecules in invertebrates (Downer et al, 1993;Kutsukake et al, 2000;Anton et al, 2006;Farooqui, 2007;Kononenko et al, 2009). Unlike in vertebrate species, however, they appear to serve the role of bona fide neurotransmitters in invertebrates, functioning as invertebrate versions of vertebrate adrenergic systems (Roeder, 2005;Lange, 2009;Homberg et al, 2013).…”

“…As previously described, although less well studied, TYR effects generally appear to functionally oppose those of OCT. As such, TYR-mediated decreases in locomotion (Nagaya et al, 2002;Saraswati et al, 2004), flying behavior (Fussnecker et al, 2006;Vierk et al, 2009), and foraging (Barron et al, 2002;Schulz et al, 2003) have been seen. Roles in sensory perception, particularly taste (Scheiner et al, 2002;Pankiw and Page, 2003) and olfaction (Kutsukake et al, 2000;Anton et al, 2006;Kononenko et al, 2009;Ma et al, 2015), have also been ascribed to TYR. TYRinduced increases in the rate of habituation (Braun and Bicker, 1992) and modification of complex group dynamics (Ma et al, 2015) are reported to occur independently of the conversion of TYR to OCT.…”

Review of octopamine in insect nervous systems

“…Release and uptake of tyramine in insects may modulate many physiological and behavioral changes related to insect behaviors. 151,175,176 …”

Octopamine and tyramine regulate the activity of reproductive visceral muscles in the adult female blood-feeding bug, Rhodnius prolixus

“…Octopamine and its precursor tyramine are both derivatives of the amino acid tyrosine, and octopamine and tyramine are believed to function analogously to adrenaline (epinephrine) and noradrenaline (norepinephrine) in vertebrates (Roeder, 2005). Thus, tyramine is now considered to be a neuroactive chemical in its own right, independent of octopamine (Kononenko et al, 2009;Lange, 2009). Octopamine and tyramine regulate diverse physiological and behavioural processes such as courtship, locomotion, learning and memory, and reproduction (Avila et al, 2012;Huang et al, 2016;Roeder, 1999;Selcho et al, 2012).…”