Serotonergic modulation of crayfish hindgut

Neuroscience Institute, Georgia State University, Atlanta, Georgia 30302-5030, USA.
Biological Bulletin (Impact Factor: 1.64). 09/2009; 217(1):50-64.
Source: PubMed


The crayfish hindgut is a morphologically differentiated tube that varies along its length in the distribution of muscles and glands, contractile properties, serotonergic innervation, patterns of 5-HT receptor expression, and sensitivity to serotonin (5-HT). Anatomical differences divide the hindgut into five distinct segments along its length. Spontaneous pulsatile contractions produced by the isolated hindgut decrease in force and increase in frequency along the anterior-posterior axis. Central input to the hindgut comes from a large cluster of 5-HT-immunoreactive neurons in the terminal abdominal ganglion that form a large nerve plexus on the hindgut. 5-HT(1alpha) and 5-HT(2beta) receptors vary in their distribution along the hindgut, and are associated with longitudinal and circular muscles and with axon collaterals of the 5-HT-immunoreactive neurons. Application of 30 nmol l(-1) to 1 mumol l(-1) 5-HT to rostral, middle, or caudal sections of hindgut produced tension changes that varied with the concentration and section. 5-HT also initiated antiperistaltic waves in the posterior hindgut. These results indicate that 5-HT is an important neuromodulator for initiating contractions and coordinating activity in the different functional compartments along the rostral-to-caudal axis of the hindgut.

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    • "This sustained slow contraction is ideal for movement of wastes along the hindgut and expulsion of feces (Brenner and Wilkens 2001; Wrong et al. 2003). Distinct physiological regions of the hindgut are evident that respond in different ways to neuromodulators (Musolf et al. 2009). For example , the posterior portion of the hindgut acts not only to expel feces but also functions in ion and water uptake (Mykles 1979; Factor 1995) and this region of the gut can undergo forward or reverse peristalsis depending on the animal's needs (Ebara 1969; Mercier and Lee 2002). "
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    ABSTRACT: The purpose of the report is to describe dissection techniques for preparing the crayfish hindgut and to demonstrate how to make physiological recordings with a force transducer to monitor the strength of contraction. In addition, we demonstrate how to visually monitor peristaltic activity, which can be used as a bioassay for various peptides, biogenic amines and neurotransmitters. This preparation is amenable to student laboratories in physiology and for demonstrating pharmacological concepts to students. This preparation has been in use for over 100 years, and it still offers much as a model for investigating the generation and regulation of peristaltic rhythms and for describing the mechanisms underlying their modulation. The pharmacological assays and receptor sub-typing that were started over 50 years ago on the hindgut still contribute to research today. This robust preparation is well suited to training students in physiology and pharmacology.
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