Abstract
Presynaptic inhibition exerted by the common inhibitor on the closer and opener muscles and by the specific inhibitor on the opener muscle was investigated in the crab Eriphia spinifrons. In the closer muscle, activation of GABAB receptors by baclofen reduced the mean quantal content of excitatory junctional currents by about 25%. Blocking GABAB receptors with CGP 55845 diminished presynaptic inhibition at a similar percentage. GABAB receptor-mediated presynaptic inhibition is linked to G proteins. Application of pertussis toxin eliminated about 25% of the inhibition exerted by the common inhibitory neuron. GABAB receptors participate in presynaptic inhibition at release boutons of the slow and the fast closer excitor at a similar percentage. In the opener muscle, presynaptic inhibition of transmitter release from the same endings of the opener excitor was about 15% stronger with the specific inhibitor than with the common inhibitor. About 10% of the presynaptic inhibition produced by either one of the two inhibitors could be abolished by blocking GABAB receptors. The amplitudes of the excitatory junctional currents in the opener were reduced in the presence of baclofen by about 25%, suggesting that synaptic terminals of the opener excitor are endowed with a similar percentage of GABAB receptors as terminals of the slow and the fast closer excitors. Baclofen had no effect on postsynaptic inhibition, indicating that GABAB receptors are not involved in postsynaptic neuromuscular inhibition.
Similar content being viewed by others
Author information
Authors and Affiliations
Additional information
Accepted: 8 January 2000
Rights and permissions
About this article
Cite this article
Rathmayer, W., Djokaj, S. Presynaptic inhibition and the participation of GABAB receptors at neuromuscular junctions of the crab Eriphia spinifrons . J Comp Physiol A 186, 287–298 (2000). https://doi.org/10.1007/s003590050429
Issue Date:
DOI: https://doi.org/10.1007/s003590050429