Glutamatergic control of a pattern-generating central nucleus in a gymnotiform fish

Abstract

The activity of central pattern-generating networks (CPGs) may change under the control exerted by various neurotransmitters and modulators to adapt its behavioral outputs to different environmental demands. Although the mechanisms underlying this control have been well established in invertebrates, most of their synaptic and cellular bases are not yet well understood in vertebrates. Gymnotus omarorum, a pulse-type gymnotiform electric fish, provides a well-suited vertebrate model to investigate these mechanisms. G. omarorum emits rhythmic and stereotyped electric organ discharges (EODs), which function in both perception and communication, under the command of an electromotor CPG. This nucleus is composed of electrotonically coupled intrinsic pacemaker cells, which pace the rhythm, and bulbospinal projecting relay cells that contribute to organize the pattern of the muscle-derived effector activation that produce the EOD. Descending influences target CPG neurons to produce adaptive behavioral electromotor responses to different environmental challenges. We used electrophysiological and pharmacological techniques in brainstem slices of G. omarorum to investigate the underpinnings of the fast transmitter control of its electromotor CPG. We demonstrate that pacemaker, but not relay cells, are endowed with ionotropic and metabotropic glutamate receptor subtypes. We also show that glutamatergic control of the CPG likely involves two types of synapses contacting pacemaker cells, one type containing both AMPAR-NMDAR receptors and the other one only-NMDAR. Fast neurotransmitter control of vertebrate CPGs seems to exploit the kinetics of the involved postsynaptic receptors to command different behavioral outputs. The prospect of common neural designs to control CPG activity in vertebrates is discussed.

Glutamate–GABA imbalance mediated by miR-8-5p and its STTM regulates phase-related behavior of locusts

“…However, the respective metabotropic receptors did not play a significant role in the phase-related behavioral regulation of locusts. In fact, different neurotransmitters evoke postsynaptic electrical responses and promote behavioral change by combining with a diverse group of postsynaptic receptors ( 40 ). Thus, our results provide a more comprehensive understanding of the molecular mechanism underlying phase changes in locusts through glutamate–GABA neurotransmission and the dopamine pathway.…”