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Vascular responses and noradrenaline overflows in the isolated blood‐perfused cat spleen: some effects of cocaine, normetanephrine and α‐blocking agents
Author(s) -
Cripps Heather,
Dearnaley D. P.
Publication year - 1972
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1972.sp010052
Subject(s) - phenoxybenzamine , normetanephrine , orthodromic , medicine , spleen , endocrinology , chemistry , anesthesia , stimulation , catecholamine , receptor
1. Vascular responses and noradrenaline overflows have been studied in the isolated blood‐perfused cat spleen in response to electrical stimulation of the splenic nerve with trains of 200 supramaximal pulses at a frequency of 10 Hz given at 10 min intervals. 2. In the absence of blocking agents the spleen gave well‐defined responses and a mean maximum overflow of 436 ± 96 pg noradrenaline per stimulus ( n = 4) at the third train of stimuli. 3. Cocaine (2 × 10 −5 M ) increased the response nearly threefold and raised the overflow to 840 ± 131 pg/stim ( n = 4). At later stimulations the responses remained stable, but the overflows rose progressively to 1076 ± 51 pg/stim after five trains of stimuli. 4. Normetanephrine (10 −4 M ) had no significant effect on response, but elevated the overflow to a mean maximum of 868 ± 169 pg/stim ( n = 4). 5. Cocaine (2 × 10 −5 M ) and normetanephrine (10 −4 M ) given together increased the response by a factor of 6·5 and raised the overflow to 1258 ± 247 pg/stim ( n = 4). 6. Hydergine (approx. 10 −5 M ) almost completely abolished the response and raised the overflow to 859 ± 173 pg/stim ( n = 4). 7. Cocaine (2 × 10 −5 M ), normetanephrine (10 −4 M ) and hydergine (approx. 10 −5 M ) given in combination abolished the response and raised the overflow to 4089 ± 1148 pg/stim ( n = 4). 8. Phenoxybenzamine (10 −4 M ) abolished the response and elevated the overflow to 4215 ± 738 pg/stim ( n = 4). 9. These results are interpreted in terms of selective and combined block of ‘uptake I’, ‘uptake II’ and α‐adrenergic receptors. Facilitation of transmitter release by α‐blocking drugs, and the possible existence of an uptake process associated with the α‐receptors are discussed.