GABAA Receptor Subunit Composition Drives Its Sensitivity to the Insecticide Fipronil

Recent advances on the influence of fipronil on insect behavior

Fipronil, a pesticide widely used to control agricultural and household insect pests, blocks insect GABAA and glutamate (GluCl) ionotropic receptors, resulting in uncontrolled hyperexcitation and paralysis that eventually leads to death. The use of fipronil is controversial because unintentional exposure to this compound may contribute to the ongoing global decline of insect pollinator populations. Although the sublethal effects of fipronil have been linked to aberrant behavior and impaired olfactory learning in insects, the precise mechanisms involved in these responses remain unclear. In this article, we highlight recent studies that have investigated the interaction among different pathways involved in the ability of fipronil to modulate insect behavior, with particular emphasis on the role of GABAergic neurotransmission in fine-tuning the integration of sensorial responses and insect behavior. Recent findings suggest that fipronil can also cause functional alterations that affect synaptic organization and the availability of metal ions in the brain.

Immunoassays and Emerging Analytical Techniques of Fipronil and its Metabolites for Food Safety: A Review

Fipronil, classified as a phenylpyrazole insecticide, is utilized to control agricultural, public health, and veterinary pests. Notably, its unique ecological fate involves degradation to toxic metabolites, which poses the risk of contamination in water and foodstuffs and potential human exposure through the food chain. In response to these concerns, there is a pressing need to develop analytical methodologies for detecting fipronil and its metabolites. This review provides a concise overview of the mode of action, metabolism, and toxicology of fipronil. Additionally, various detection strategies, encompassing antibody-based immunoassays and emerging analytical techniques, such as fluorescence assays based on aptamer/molecularly imprinted polymer/fluorescent probes, electrochemical sensors, and Raman spectroscopy, are thoroughly reviewed and discussed. The focus extends to detecting fipronil and its metabolites in crops, fruits, vegetables, animal-derived foods, water, and bodily fluids. This comprehensive exploration contributes valuable insights into the field, aiming to foster the development and innovation of more sensitive, rapid, and applicable analytical methods.

Microtransplantation of Synaptic Membranes to Reactivate Human Synaptic Receptors for Functional Studies

Excitatory and inhibitory ionotropic receptors are the major gates of ion fluxes that determine the activity of synapses during physiological neuronal communication. Therefore, alterations in their abundance, function, and relationships with other synaptic elements have been observed as a major correlate of alterations in brain function and cognitive impairment in neurodegenerative diseases and mental disorders. Understanding how the function of excitatory and inhibitory synaptic receptors is altered by disease is of critical importance for the development of effective therapies. To gain disease-relevant information, it is important to record the electrical activity of neurotransmitter receptors that remain functional in the diseased human brain. So far this is the closest approach to assess pathological alterations in receptors' function. In this work, a methodology is presented to perform microtransplantation of synaptic membranes, which consists of reactivating synaptic membranes from snap frozen human brain tissue containing human receptors, by its injection and posterior fusion into the membrane of Xenopus laevis oocytes. The protocol also provides the methodological strategy to obtain consistent and reliable responses of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and γ-aminobutyric acid (GABA) receptors, as well as novel detailed methods that are used for normalization and rigorous data analysis.

Safety of oral afoxolaner formulated with or without milbemycin oxime in homozygous MDR1-deficient collie dogs

Afoxolaner, an insecticide and acaricide compound of the isoxazoline class, is available for dogs as an oral ectoparasiticide medicine (NexGard®) and as an oral endectoparasiticide medicine in combination with milbemycin oxime (MO), a macrocyclic lactone (NexGard® Spectra). The safety of these two compounds, alone or in combination, was investigated in homozygous MDR1‐deficient collie dogs, in two studies. Overall, 30 adult collie dogs were treated once orally, 9 with a placebo, 9 with afoxolaner, 6 with MO, and 6 with a combination of afoxolaner and MO. For afoxolaner, the mean investigated dosage corresponded to 3.8 and 4.7 multiples of the maximum recommended therapeutic doses (RTD) in NexGard® and NexGard® Spectra, respectively. For MO, the mean investigated dosage corresponded to 4.7 multiples of the maximum RTD in NexGard® Spectra. Dogs were closely monitored for adverse reactions on the day of treatment and for the following two days. No significant adverse reaction was observed in any dog from the afoxolaner or the afoxolaner + MO groups; in the MO‐only treated group, mild and transient neurological signs were observed during the 4–8 h post‐treatment window. These studies demonstrated a high level of safety of oral afoxolaner, alone or in combination with milbemycin oxime, in homozygous MDR1‐deficient dogs.