Static stretching provides benefits to the range of motion, modulates intramuscular connective tissue, and is incorporated into warm-up exercises. In this study, we present the effects in the motor endplate and belly muscle resulting from previous static stretching to climbing training. Twenty-four adult male Wistar rats were divided into four groups (n = 6 each): Sedentary (Sed), Climbing (Clb), Static stretching (Ss), and Static stretching prior to climbing (Ssc). The animals (Clb, Ss, and Ssc groups) were subjected to a training protocol 3×/week for 8 weeks, and the Ssc group was subjected to the Ss and Clb protocols in the same session. Samples from the animals were processed for immunostaining, histochemistry, and light microscopy. The Clb group presented a higher motor endplate; the Ss group presented no changes in the motor endplate; and the Ssc group demonstrated a higher compactness. We concluded that static stretching prior to the climbing protocol maintained the density of the motor endplate and increased the compactness of the neuromuscular junction structure. Also, there was a reduction in the myofibers’ diameter (Type I and IIa), an increase in myofibrillar densities (Type I and IIx, and total), and the reorganization of the myonuclei and the interstitium.

A rabbit antiserum was raised against a synthetic peptide corresponding to a region near the N-terminus of the Haemonchus contortus inhibitory amino acid receptor subunit, HG1. The antiserum recognized a recombinant form of the N-terminal domain of the subunit on Western blots and reacted with the ventral nerve cord of H. contortus in immunofluorescence experiments. Immunofluorescence was also detected in specific head neurons of H. contortus: these were tentatively identified as ring motor- and inter-neurons, plus a possible sensory neuron equivalent to the AQR cell of Caenorhabditis elegans. In the roundworm Ascaris suum, immunoreactivity was limited to the muscle arms, the post-synaptic component of the neuromuscular junction. The possible ligand of receptors containing the HG1 subunit is discussed in the light of this expression pattern.

5-Hydroxytryptamine has wide-ranging effects on a number of physiological systems. In addition the exogenous application of 5-hydroxytryptamine or 5-hydroxytryptamine type drugs to tissue bath preparations has revealed the presence of a large and ever growing population of 5-hydroxytryptamine receptors. The discovery that 5-hydroxytryptamine is released at the neuromuscular junction raises the question as to whether it has a physiological function and whether or not applying low concentrations of 5-hydroxytryptamine transmitter would have any significant effect on twitch response at different rates of stimulation. Previous studies have demonstrated both facilitatory and depressant effects upon twitch responses in a variety of animal models. Single twitch responses of the rat phrenic nerve diaphragm preparation at non-fatiguing (0.3 Hz) and tetanic rates of stimulation (50 Hz) were recorded under conditions of indirect (nerve) stimulation at 4 g resting tension. The preparation was incubated with 0.5, 1, 2, 4, 16 μmol litre−1 concentrations of 5-hydroxytryptamine. The results of our investigations demonstrate that while low concentrations of 5-hydroxytryptamine have no effect upon the single twitch response at resting rates of stimulation (0.3 Hz), the initial single twitch and the subsequent eighteen responses immediately following a tetanus are facilitated (P<0.05). This work demonstrates that 5-hydroxytryptamine does have significant effects upon the neuromuscular junction under conditions of physiological compromise (following tetanus). These observations are the first step, therefore, in a series of studies aimed at identifying the resident 5-hydroxytryptamine receptors within the neuromuscular junction which will subsequently enable us to predict therapeutic effect or toxicity.

The actions of diisopropylfluorophosphate (DFP), an irreversible anticholinestrase (Anti-ChE) agent, were studied on the glutamatergic neuromuscular synapse of insects. The present study reveals that DFP interacts with pre- and post-synaptic regions, also it gives alternative explanations of the symptoms of organophosphate poisoning in insects. Exposure of the metathoracic flexor tibialis muscle of Locusta migratoria to DFP (0.5 mM), at physiological solution, contained normal external calcium concentration (2 mM), increased spontaneous neurotransmitter release which was large enough to trigger action potentials (APs) and endplate potentials (EPPs). A cyclic pattern of APs and EPPs burses and silence periods were recorded. The spontaneous firing of APs and EPPs was calcium-dependent. Reduction of external calcium concentration abolished this phenomenon, suggesting a pre-synaptic site of action of DFP. A transient pre-synaptic depolarization, caused by the agent, could explain the spontaneous transmitter release and repetitive EPPs firing. The spontaneous activity, induced by DFP, was blocked by a sodium channel blocker such as tetrodotoxin. Exposure to α-bungarotoxin, α-Naja-toxin or atropine did not affect the spontaneous release of the transmitter induced by OP agent. Coupled with the pre-synaptic effect, a decrease in the peak amplitude of endplate current (EPC) and shortening of the decay time constant (τEPC) recorded after exposure to the flexor muscle to 1 mM DFP. Both the pre- and post-synaptic effects of DFP were reversible upon washing the preparation. The present findings shift the focus of the occasioners of hyperexcitation of insects treated with OPs from indirect effects of these compounds on the central nervous system (CNS) to direct effects on neuromuscular junctions and indirect effects on CNS.