Tachykinins as mediators of slow EPSPs in guinea-pig gall-bladder ganglia: involvement of neurokinin-3 receptors
Abstract
1. The effects of endogenous tachykinins and related peptides on intact guinea-pig gall-bladder neurones were investigated with single-electrode voltage- and current-clamp recording techniques. 2. Pressure ejection of substance P (100 microM) caused a long lasting membrane depolarization that was associated with a decrease in input resistance. In cells that were voltage-clamped to their resting membrane potential, substance P activated an inward current. 3. The reversal potentials of the substance P-induced depolarization and inward current were congruent to 0 mV. In a low-Na+ solution, the substance P-induced depolarization and inward current were reduced in amplitude. 4. Substance P increased the excitability of neurones, as evidenced by a greater anodal break activity and an increase in the number of action potentials generated during a depolarizing current pulse. 5. Substance P, neurokinin A (NKA) and neurokinin B (NKB) were applied by superfusion to determine the relative potencies of these tachykinins. NKB was the most potent, with an EC50 of 24 nM. The EC50 values for NKA and substance P were 47.8 and 281 nM, respectively. 6. The neurokinin-3 (NK-3) receptor agonist senktide depolarized neurones with an EC50 of 6.3 nM. N...Continue Reading
Citations
Endogenous neurokinins facilitate synaptic transmission in guinea pig airway parasympathetic ganglia
Substance P modulates nicotinic responses of intracardiac neurons to acetylcholine in the guinea pig
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