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. 1974 Dec;52(4):549–557. doi: 10.1111/j.1476-5381.1974.tb09723.x

Protection by phentolamine against the effects of phenoxybenzamine on transmitter release elicited by nerve stimulation in the perfused cat heart

MB Farah, SZ Langer
PMCID: PMC1776890  PMID: 4376039

Abstract

1 The effects of cocaine, phentolamine and phenoxybenzamine on neuronal uptake of [3H]-noradrenaline and on 3H-transmitter and noradrenaline overflow elicited by nerve stimulation were determined in the perfused heart of the cat.

2 During perfusion with cocaine 3.4 × 10-7M, there was a 2-fold increase in transmitter overflow while neuronal uptake of [3H]-noradrenaline was inhibited by 31.3 ± 2.1%.

3 After exposure to phenoxybenzamine 8.7 × 10-7 M for 20 min and washing with drug-free solution for 165 min there was an 8-fold increase in transmitter overflow during nerve stimulation. Under these conditions neuronal uptake of [3H]-noradrenaline was inhibited by only 17.5 ± 5.4%.

4 There was no significant change in transmitter overflow or in neuronal uptake of [3H]-noradrenaline, 155 min after a 30 min exposure to phentolamine (3.2 × 10-5M).

5 Perfusion with phentolamine (3.2 × 10-5M) before and during exposure to phenoxybenzamine (8.7 × 10-7M), prevented the increase in transmitter overflow observed after perfusion with phenoxybenzamine alone.

6 Protection by phentolamine against the effects of phenoxybenzamine supports the view that the effects on transmitter release obtained after perfusion with phenoxybenzamine are due to the blockade of presynaptic α-adrenoceptors which regulate transmitter release through a negative feed-back mechanism.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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