Distribution and physiological effects of B-type allatostatins (myoinhibitory peptides, MIPs) in the stomatogastric nervous system of the crab Cancer borealis.

The crustacean stomatogastric ganglion (STG) is modulated by a large number of amines and neuropeptides that are found in descending pathways from anterior ganglia or reach the STG via the hemolymph. Among these are the allatostatin (AST) B types, also known as myoinhibitory peptides (MIPs). We used mass spectrometry to determine the sequences of nine members of the AST-B family of peptides that were found in the stomatogastric nervous system of the crab Cancer borealis.

Fast synaptic transmission in the goldfish CNS mediated by multiple nicotinic receptors.

Usually nicotinic receptors in the central nervous system only influence the strength of a signal between neurons. At a few critical connections, for instance some of those involved in the flight response, nicotinic receptors not only modulate the signal, they actually determine whether a signal is conveyed or not. We show at one of the few such connections accessible for study, up to three different nicotinic receptor subtypes mediate the signal.

Serotonin regulates electrical coupling via modulation of extrajunctional conductance: H-current.

Synaptic strength can be highly variable from animal to animal within a species or over time within an individual. The process of synaptic plasticity induced by neuromodulatory agents might be unpredictable when the underlying circuits subject to modulation are themselves inherently variable. Serotonin (5-hydroxytryptomine; 5HT) and serotonergic signaling pathways are important regulators of animal behavior and are pharmacological targets in a wide range of neurological disorders.

Mass spectrometric characterization and physiological actions of novel crustacean C-type allatostatins.

The crustacean stomatogastric ganglion (STG) is modulated by numerous neuropeptides that are released locally in the neuropil or that reach the STG as neurohormones. Using 1,5-diaminonaphthalene (DAN) as a reductive screening matrix for matrix-assisted laser desorption/ionization (MALDI) mass spectrometric profiling of disulfide bond-containing C-type allatostatin peptides followed by electrospray ionization quadrupole time-of-flight (ESI-Q-TOF) tandem mass spectrometric (MS/MS) analysis, we identified and sequenced a novel C-type allatostatin peptide (CbAST-C1), pQIRYHQCYFNPISCF-COOH, present in the pericardial organs of the crab, Cancer borealis. Another C-type allatostatin (CbAST-C2), SYWKQCAFNAVSCFamide, was discovered using the expressed sequence tag (EST) database search strategy in both C.

Effects of temperature acclimation on a central neural circuit and its behavioral output.

In this study, we address the impact of temperature acclimation on neuronal properties in the Mauthner (M-) system, a brain stem network that initiates the startle-escape behavior in goldfish. The M-cell can be studied at cellular and behavioral levels, since it is uniquely identifiable physiologically within the intact vertebrate brain, and a single action potential in this neuron determines not only whether a startle response will occur but also the direction of the escape. Using animals acclimated to 15 degrees C as a control, 25 degrees C-acclimated fish showed a significant increase in escape probability and a decrease in the ability to discriminate escape directionality.

Behavioral and physiological characterization of sensorimotor gating in the goldfish startle response.

Prepulse inhibition (PPI) is typically associated with an attenuation of auditory startle behavior in mammals and is presumably mediated within the brainstem startle circuit. However, the inhibitory mechanisms underlying PPI are not yet clear. We addressed this question with complementary behavioral and in vivo electrophysiological experiments in the startle escape circuit of goldfish, the Mauthner cell (M-cell) system.

Otolith endorgan input to the Mauthner neuron in the goldfish.

The Mauthner (M-) cell of the goldfish, Carassius auratus, triggers the rapid escape response of the fish in response to various stimuli, including visual and auditory. The large size and accessibility of the M-cell make it an ideal model system for the study of synaptic transmission, membrane properties, and sensory-motor gating. Although physiological recordings have suggested that afferents from all three of the inner ear endorgans (the saccule, lagena, and utricle) synapse directly on the ipsilateral M-cell, the specific contacts and anatomical distributions of these inputs along the M-cell lateral dendrite remain unknown.

Transient electrical coupling regulates formation of neuronal networks.

Electrical synapses are abundant before and during developmental windows of intense chemical synapse formation, and might therefore contribute to the establishment of neuronal networks. Transient electrical coupling develops and is then eliminated between regenerating Helisoma motoneurons 110 and 19 during a period of 48-72 h in vivo and in vitro following nerve injury. An inverse relationship exists between electrical coupling and chemical synaptic transmission at these synapses, such that the decline in electrical coupling is coincident with the emergence of cholinergic synaptic transmission.

Transient electrical coupling delays the onset of chemical neurotransmission at developing synapses.

The formation and subsequent elimination of electrical coupling between neurons has been demonstrated in many developing vertebrate and invertebrate nervous systems. The relationship between the disappearance of electrical synaptic connectivity and the appearance of chemical neurotransmission is not well understood. We report here that identified motoneurons from the snail Helisoma formed transient electrical and chemical connections during regeneration both in vivo and in vitro.