Natural light is regarded as a key regulator of biological systems and typically serves as a Zeitgeber for biological rhythms. As a natural abiotic factor, it is recognized to regulate multiple behavioral and physiological processes in animals. Disruption of the natural light regime due to light pollution may result in significant effects on animal learning and memory development. Here, we investigated whether sensitivity to various photoperiods or light intensities had an impact on intermediate-term memory (ITM) and long-term memory (LTM) formation in the pond snail Lymnaea stagnalis . We also investigated the change in the gene expression level of molluscan insulin-related peptide II (MIP II) is response to the given light treatments. The results show that the best light condition for proper LTM formation is exposure to a short day (8 h light) and low light intensity (1 and 10 lx). Moreover, the more extreme light conditions (16 h and 24 h light) prevent the formation of both ITM and LTM. We found no change in MIP II expression in any of the light treatments, which may indicate that MIP II is not directly involved in the operant conditioning used here, even though it is known to be involved in learning. The finding that snails did not learn in complete darkness indicates that light is a necessary factor for proper learning and memory formation. Furthermore, dim light enhances both ITM and LTM formation, which suggests that there is an optimum since both no light and too bright light prevented learning and memory. Our findings suggest that the upsurge of artificial day length and/or night light intensity may also negatively impact memory consolidation in the wild.
Proteins encoded by nanchung, inactive, nompC and piezo genes have been shown to play crucial roles in the initial detection of mechanical force by various insect auditory neurons, nociceptors and touch receptors. Most of this previous research has been performed on the larval and adult fruit fly, Drosophila melanogaster. We identified and assembled all four homologous genes in transcriptomes from the cockroach, Periplaneta americana. Injection of long double-stranded RNA (dsRNA) into the adult cockroach abdomen successfully reduced the expression of each gene, as measured by quantitative PCR (RT-qPCR). A simple electrophysiological assay was used to record action potential firing in afferent nerves of cockroach femoral tactile spines in response to a standardized mechanical step displacement. Responses of nanchung knockdown animals were significantly reduced compared to matched sham-injected animals at 14 and 21 days after injection, and inactive knockdowns similarly at 21 days. In contrast, responses of nompC and piezo knockdowns were unchanged. Our results support a model in which Nanchung and Inactive proteins combine to form a part of the mechanotransduction mechanism in the cockroach tactile spine.
Impairment of the dopamine system is the main cause of Parkinson disease (PD). PTEN-induced kinase 1 (PINK1) is possibly involved in pathogenesis of PD. However, its role in dopaminergic neurons has not been fully established yet. In the present investigation, we have used the PINK1 knockout Drosophila model to explore the role of PINK1 in dopaminergic neurons. Electrophysiological and behavioral tests indicated that PINK1 elimination enhances the neural transmission from the presynaptic part of dopaminergic neurons in the protocerebral posterior medial region 3 (PPM3) to PPM3 neurons (which are homologous to those in the substantia nigra in humans). Firing properties of the action potential in PPM3 neurons were also altered in the PINK1 knockout genotypes. Abnormal motor ability was also observed in these PINK1 knockout animals. Our results indicate that knockout of PINK1 could alter both the input and output properties of PPM3 neurons.
Tricaine mesylate, also known as MS-222, was investigated to characterize its effects on sensory neurons, synaptic transmission at the neuromuscular junction, and heart rate in invertebrates. Three species were examined: Drosophila melanogaster, blue crab (Callinectes sapidus), and red swamp crayfish (Procambarus clarkii). Intracellular measures of action potentials in motor neurons of the crayfish demonstrated that MS-222 dampened the amplitude, suggesting that voltage-gated Na + channels are blocked by MS-222. This is likely the mechanism behind the reduced activity measured in sensory neurons and depressed synaptic transmission in all three species as well as reduced cardiac function in the larval Drosophila. To address public access to data, a group effort was used for analysis of given data sets, blind to the experimental design, to gauge analytical accuracy. The determination of a threshold in analysis for measuring extracellular recorded sensory events is critical and is not easily performed with commercial software.
In decapods, dopamine, octopamine, serotonin, and histamine function as locally released/hormonally delivered modulators of physiology/behavior. Although the functional roles played by amines in decapods have been examined extensively, little is known about the identity/diversity of their amine receptors. Recently, a Homarus americanus mixed nervous system transcriptome was used to identify putative neuronal amine receptors in this species. While many receptors were identified, some were fragmentary, and no evidence of splice/other variants was found. Here, the previously predicted proteins were used to search brain- and eyestalk ganglia-specific transcriptomes to assess/compare amine receptor complements in these portions of the lobster nervous system. All previously identified receptors were reidentified from the brain and/or eyestalk ganglia transcriptomes, i.e., dopamine alpha-1, beta-1, and alpha-2 (Homam-DAα2R) receptors, octopamine alpha (Homam-OctαR), beta-1, beta-2, beta-3, beta-4, and octopamine–tyramine (Homam-OTR-I) receptors, serotonin type-1A, type-1B (Homam-5HTR1B), type-2B, and type-7 receptors; and histamine type-1 (Homam-HA1R), type-2, type-3, and type-4 receptors. For many previously partial proteins, full-length receptors were deduced from brain and/or eyestalk ganglia transcripts, i.e., Homam-DAα2R, Homam-OctαR, Homam-OTR-I, and Homam-5HTR1B. In addition, novel dopamine/ecdysteroid, octopamine alpha-2, and OTR receptors were discovered, the latter, Homam-OTR-II, being a putative paralog of Homam-OTR-I. Finally, evidence for splice/other variants was found for many receptors, including evidence for some being assembly-specific, e.g., a brain-specific Homam-OTR-I variant and an eyestalk ganglia-specific Homam-HA1R variant. To increase confidence in the transcriptome-derived sequences, a subset of receptors was cloned using RT-PCR. These data complement/augment those reported previously, providing a more complete picture of amine receptor complement/diversity in the lobster nervous system.
