Effects of Ethanol on Sensory Inputs to the Medial Giant Interneurons of Crayfish

Abstract

Crayfish are capable of two rapid, escape reflexes that are mediated by two pairs of giant interneurons, the lateral giants (LG) and the medial giants (MG), which respond to threats presented to the abdomen or head and thorax, respectively. The LG has been the focus of study for many decades and the role of GABAergic inhibition on the escape circuit is well-described. More recently, we demonstrated that the LG circuit is sensitive to the acute effects of ethanol and this sensitivity is likely mediated by interactions between ethanol and the GABAergic system. The MG neurons, however, which receive multi-modal sensory inputs and are located in the brain, have been less studied despite their established importance during many naturally occurring behaviors. Using a combination of electrophysiological and neuropharmacological techniques, we report here that the MG neurons are sensitive to ethanol and experience an increase in amplitudes of post-synaptic potentials following ethanol exposure. Moreover, they are affected by GABAergic mechanisms: the facilitatory effect of acute EtOH can be suppressed by pretreatment with a GABA receptor agonist whereas the inhibitory effects resulting from a GABA agonist can be occluded by ethanol exposure. Together, our findings suggest intriguing neurocellular interactions between alcohol and the crayfish GABAergic system. These results enable further exploration of potentially conserved neurochemical mechanisms underlying the interactions between alcohol and neural circuitry that controls complex behaviors.

The giant escape neurons of crayfish: Past discoveries and present opportunities

“…Mellon and Christison-Lagay (2008) demonstrated that electrical stimulation of the bases of the antennules (i.e., antenna I) evoked action potentials in crayfish MG neurons, and the authors suggested that these inputs are mediated by mechanosensory hairs located on the flagella of the antennules. Similar results have been obtained after electrical stimulation of the antenna II nerve, which strongly depolarized the MG neurons and occasionally caused action potentials (Liu and Herberholz 2010;Swierzbinski and Herberholz 2018).…”

“…Soon after, Swierzbinski and Herberholz (2018) showed that EtOH also facilitated the response of the MG neurons to sensory inputs. In addition, the authors highlighted the role of the GABAergic system in mediating this effect.…”

Behavioral effects of ethanol in the Red Swamp Crayfish (Procambarus clarkii)

“…Crayfish species are widely distributed, worldwide, in natural environments (https://en.wikipedia.org/wiki/Crayfish). Subjects for use in laboratory experiments can be purchased from pet stores (as we did for some of our subjects), biological suppliers (Swierzbinski & Herberholz, 2018; Teshiba et al, 2001), or are easily fished from the wild, if locally available (Datta et al, 2018; Imeh‐Nathaniel et al, 2017). This invertebrate species can be used for research within institutions that do not maintain regulatory approvals and facilities appropriate for vertebrate animal research subjects.…”

Behavioral effects of ethanol in the Red Swamp Crayfish (Procambarus clarkii)

“…Crayfish species are widely distributed, worldwide, in natural environments (https://en.wikipedia.org/wiki/Crayfish). Subjects for use in laboratory experiments can be purchased from pet stores (as we did for some of our subjects), biological suppliers (Swierzbinski and Herberholz, 2018; Teshiba et al, 2001), or are easily fished from the wild, if locally available (Datta et al, 2018; Imeh-Nathaniel et al, 2017). This invertebrate species can be used for research within institutions that do not maintain regulatory approvals and facilities appropriate for vertebrate animal research subjects.…”