Immunohistochemical localization and electrophysiological action of nociceptin/orphanin-FQ in the snail (Helix aspersa) neurons

The Effect of Valproate Sodium on the Electrical Activity of Helix aspersa F1 Neurons in a Pentylenetetrazole-Induced Epileptic Model Using an Intracellular Recording System

Background: Epilepsy is a chronic central nervous system disorder with a high prevalence in modern society. Despite using common anticonvulsant drugs, its control is not adequately achieved. Animal models for seizures play the leading role in advancing our understanding of the cellular mechanisms of epilepsy. The present study was an attempt to elucidate the electrophysiological mechanism of the effect of sodium valproate on the cellular model of epilepsy. Understanding the cellular mechanisms of this drug may help clarify the pharmacological screening of other drugs. Methods: The intracellular recording was made from F1 cells of garden Helix aspersa in the presence of Ringer solution. Following the extracellular application of valproate sodium at a concentration of 10 mM after and before the use of (25mM) epileptogenic agent (pentylenetetrazol (PTZ)), we evaluated its effect on paroxysmal depolarization shift (PDS) and electrophysiological characteristics. Results: These results showed that valproate sodium could reduce neuronal excitability. It could significantly hyperpolarize rest action potential by decreasing the frequency of firing rate and increasing the amplitude of afterhyperpolarization (AHP) and can prevent depolarization of rest action potential by PTZ. Conclusions: The results suggested that valproate sodium could reduce the PTZ-induced hyperexcitation by hyperpolarization of resting membrane potential (RMP), a reduction in AHP amplitude, and firing the frequency.

Calcium-Binding Proteins in the Nervous System during Hibernation: Neuroprotective Strategies in Hypometabolic Conditions?

Calcium-binding proteins (CBPs) can influence and react to Ca²⁺ transients and modulate the activity of proteins involved in both maintaining homeostatic conditions and protecting cells in harsh environmental conditions. Hibernation is a strategy that evolved in vertebrate and invertebrate species to survive in cold environments; it relies on molecular, cellular, and behavioral adaptations guided by the neuroendocrine system that together ensure unmatched tolerance to hypothermia, hypometabolism, and hypoxia. Therefore, hibernation is a useful model to study molecular neuroprotective adaptations to extreme conditions, and can reveal useful applications to human pathological conditions. In this review, we describe the known changes in Ca²⁺-signaling and the detection and activity of CBPs in the nervous system of vertebrate and invertebrate models during hibernation, focusing on cytosolic Ca²⁺ buffers and calmodulin. Then, we discuss these findings in the context of the neuroprotective and neural plasticity mechanisms in the central nervous system: in particular, those associated with cytoskeletal proteins. Finally, we compare the expression of CBPs in the hibernating nervous system with two different conditions of neurodegeneration, i.e., platinum-induced neurotoxicity and Alzheimer's disease, to highlight the similarities and differences and demonstrate the potential of hibernation to shed light into part of the molecular mechanisms behind neurodegenerative diseases.

The nociceptin/orphanin FQ-like opioid peptide in nervous periesophageal ganglia of land snail Helix aspersa

The neuropeptide nociceptin/orphanin FQ (N/OFQ) and its receptor are members of the endogenous opioid peptide family. In mammals N/OFQ modulates a variety of biological functions such as nociception, food intake, endocrine, control of neurotransmitter release, among others. In the molluscs Cepea nemoralis and Helix aspersa the administration of N/OFQ produces a thermopronociceptive effect. However, little is known about its existence and anatomic distribution in invertebrates. The aim of this study was to provide a detailed anatomical distribution of N/OFQ like peptide immunoreactivity (N/OFQ-IL), to quantify the tissue content of this peptide, as well as to demostrate molecular evidence of N/OFQ mRNA in the nervous tissue of periesophageal ganglia of the land snail H. aspersa. Immunohistochemical, immunocytochemical, radioimmunoanalysis (RIA) and reverse transcription-polymerase chain reaction (RT-PCR) techniques were used. With regard to RT-PCR, the primers to detect expression of mRNA transcripts from H. aspersa were derived from the rat N/OFQ opioid peptide. We show a wide distribution of N/OFQ-IL in neurons and fibers in all perioesophageal ganglia, fibers of the neuropile, nerves, periganglionar connective tissue, aortic wall and neurohemal sinuses. The total amount of N/OFQ-IL in the perioesophageal ganglia (7.75 ± 1.75 pmol/g of tissue) quantified by RIA was similar to that found in mouse hypothalamus (10.1 ± 1.6 pmol/g of tissue). In this study, we present molecular evidence of N/OFQ mRNA expression. Some N/OFQ-IL neurons have been identified as neuroendocrine or involved in olfaction, hydro-electrolyte regulation, feeding, and thermonociception. Therefore, we suggest that N/OFQ may participate in these snail functions.

Nociceptin attenuates methamphetamine abstinence-induced withdrawal-like behavior in planarians

Planarians display a concentration-related reduction in locomotor activity when amphetamine, cocaine, cannabinoid, or benzodiazepine exposure is abruptly discontinued. In the present study, we tested the hypothesis that abrupt discontinuation of methamphetamine would also cause withdrawal-like behavior in planarians and that the withdrawal-like behavior would be prevented by nociceptin, which has been shown to modulate the effects of methamphetamine in mammals. We observed a concentration-related reduction of locomotor behavior when planarians exposed to methamphetamine (0.1-100 microM) were tested in drug-free water. The withdrawal-like behavior was abolished when methamphetamine (10 microM)-exposed planarians were placed into water containing nociceptin (10 microM) or when planarians co-exposed to methamphetamine (10 microM) and nociceptin (10 microM) were placed into drug-free water. The effects of nociceptin were abolished in the presence of a nociceptin receptor antagonist, JTC-801 (1 microM). Planarians did not display a change in locomotor behavior during exposure to nociceptin (10 microM) or JTC-801 (1 microM) by themselves. These results (1) reveal a functional interaction between nociceptin and methamphetamine in planarians and (2) provide evidence that nociceptin blocks methamphetamine-induced withdrawal-like behavior in planarians through a JTC-801-sensitive mechanism.

Role of nociceptin/orphanin FQ and the pseudopeptide [Phe1Psi(CH2NH)Gly2]-nociceptin(1-13)-NH2 and their interaction with classic opioids in the modulation of thermonociception in the land snail Helix aspersa

The role in nociception of nociceptin/orphanin FQ (N/OFQ) and its receptor, the opioid receptor-like 1 (NOP), remains unclear because this peptide has been implicated in both suppression and enhancement of nociception. The present work characterises the effects of N/OFQ and the NOP receptor antagonist, the pseudopeptide [Phe(1)Psi(CH(2)NH)Gly(2)]-nociceptin(1-13)-NH(2) (Phe(1)Psi), on thermonociception in the snail Helix aspersa using the hot plate assay. Additionally, the possible interaction of each of these compounds with morphine or dynorphin A(1-17) and naloxone was studied. Compounds were administered into the hemocoel cavity of H. aspersa and the latency to the aversive withdrawal behaviour recorded. Dose-response and time course curves were done. N/OFQ and naloxone produced a similar dose-dependent pronociceptive effect; however, N/OFQ reached its peak effect earlier and was 30 times more potent than naloxone. [Phe(1)Psi(CH(2)NH)Gly(2)]-nociceptin(1-13)-NH(2) and the opioid agonists, morphine and dynorphin A(1-17) produced antinociception with a similar efficacy, but [Phe(1)Psi(CH(2)NH)Gly(2)]-nociceptin(1-13)-NH(2) reached its peak effect more rapidly and lasted longer than that of dynorphin A(1-17) and morphine. [Phe(1)Psi(CH(2)NH)Gly(2)]-nociceptin(1-13)-NH(2) was 50 times less potent than dynorphin A(1-17), but 30 times more potent than morphine. N/OFQ significantly reduced morphine and dynorphin A(1-17)-induced antinociception. Combined administration of low doses of [Phe(1)Psi(CH(2)NH)Gly(2)]-nociceptin(1-13)-NH(2) and morphine or dynorphin A(1-17) produced a potent antinociceptive effect. Sub-effective doses of naloxone and N/OFQ also synergised to produce pronociception. Data suggest that these two opioid classes regulate nociception through parallel systems. The H. aspersa model appears as a valuable experimental preparation to continue the study of these opioid receptor systems.

Immunolocalization of orphanin FQ in rat cochlea

Orphanin FQ/nociceptin (OFQ/N) and its receptor (ORL-1) have been proposed to play a role in the regulation of hearing. In this study, we investigate the localization of OFQ/N-like immunoreactivity in the mammalian cochlea. Sprague-Dawley rat temporal bones were harvested and decalcified. The organ of Corti was microdissected, and indirect immunohistochemistry was performed using a rabbit polyclonal antibody raised against OFQ/N. Immunoreactivity was seen in the tunnel crossing fibers and the large boutons terminating onto outer hair cells, and in the fibers terminating onto the afferents to the inner hair cells. The findings are consistent with OFQ/N expression in lateral and medial olivocochlear efferents.