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Biomedical subjects

C Raper

Publications and source records attributed to C Raper.

At least 37 records · Page 2Linked to original sources
PubMed1972

Pharmacological actions of a new -adrenoceptor agonist, MJ-9184-1, in anaesthetized cats.

1. The effects of (-)-isoprenaline and the new beta-adrenoceptor agonist, MJ-9184-1, on the lungs, on the cardiovascular system, and on slow contracting skeletal muscle have been compared in cats under chloralose anaesthesia.2. Both amines reduced the increases in airways resistance produced by 5-HT, depressed incomplete tetanic contractions of the soleus muscle, lowered the blood pressure and produced an increase in heart rate. In comparison with (-)-isoprenaline, MJ-9184-1 had a long duration of action.3. The effects of MJ-9184-1 and (-)-isoprenaline were antagonized by the beta-adrenoceptor antagonist, propranolol.4. MJ-9184-1 was approximately half as potent as (-)-isoprenaline in its effects on pulmonary resistance and soleus muscle contractility, and one seventh as potent in producing chronotropic effects in the heart.5. These results suggest that MJ-9184-1 possesses some specificity as a beta(2) receptor stimulant.

Adrenergic beta-Agonists↗
PubMed1970

Prejunctional actions of some beta-adrenoreceptor antagonists in the vas deferens preparation of the guinea-pig.

1. The beta-adrenoceptor antagonists propranolol, pronethalol, MJ 1999 and Ciba 39089-Ba reduced responses to field stimulation of the guinea-pig isolated vas deferens preparation without significantly affecting responses to exogenously added noradrenaline.2. This prejunctional blocking action of the drugs cannot be correlated with their action as beta-adrenoceptor antagonists or non-specific depressants.3. The blockade produced was more pronounced at low (5-20 Hz) than at high (50 Hz) frequencies of stimulation.4. The blockade was slow in onset, and once established was poorly reversed by washing the preparation over a period of 1 to 2 h.5. The blockade produced could be reversed by dexamphetamine and cocaine.6. These experiments suggest that the beta-adrenoceptor antagonists may have some actions which closely resemble those of the adrenergic neurone blocking agent guanethidine.

Adrenergic beta-Antagonists↗
PubMed1969

Post-tetanic and drug-induced repetitive firing in the soleus muscle of the cat.

1. The effects of a high frequency indirect tetanus on the responses to subsequent infrequently applied nerve shocks have been compared in the tibialis anterior and soleus muscles of cats and rabbits.2. Post-tetanic augmentation of twitches in the cat soleus muscle was shown to be partly due to repetitive firing and partly due to increased synchronization of the muscle fibre response. Post-tetanic repetitive firing was not evident in the responses of the other three muscles studied.3. Post-tetanic repetitive responses in the cat soleus muscle and nerve did not originate in the nerve trunk and were not produced by direct muscle stimulation; they were abolished by doses of tubocurarine smaller than those necessary to reduce the twitch tension below the pre-tetanic level. These findings support the conclusion of others that the repetitive firing originates at the neuromuscular junction.4. The repetitive firing could not be explained by an increase in the sensitivity of the motor endplates to acetylcholine, suggesting that an increase in and/or a prolongation of the output of transmitter from the motor nerve contributes to it.5. The cat soleus muscle was shown to be more sensitive to neostigmine than were the other three muscles studied, and acetylcholinesterase determinations showed that this muscle possesses less enzyme activity.6. It is concluded that an increase in transmitter output, coupled with a weaker cholinesterase activity, probably accounts for the post-tetanic repetitive activity in the cat soleus muscle.7. Post-tetanic repetitive firing was absent in cat soleus muscles which had been cross-innervated with the nerve formerly innervating a fast-contracting muscle.

Acetylcholine↗