| RESEARCH PAPER
|Year : 1998 | Volume
| Issue : 2 | Page : 102-106
Suitability of isolated toad large intestine for bioassay of cholinomimetics
SA Igwe, G Onuaguluchi
Objective: To investigate the suitability of toad large intestine for bioassay of cholinomimetics.
Method: The effect of cholinomimetics, - ACh and carbachol (CCh) was determined using the isolated toad large intestine.The results were compared in parallel experiments using the isolated terminal guinea-pig ileum. In both preparations, equiconcentrations of agonists: 0.55, 1.1, 2.2, 4.4, X 10-6M were used and produced similar responses quantitatively. Similarly, equiconcentrations of atropine: 1.4, 2.9, 5.8, X 1 O-9M respectively produced the same degree and type of block in the two preparations.
Results: The pA2 and pD2 values in the two preparations were similar and there was no significant difference between these values and those obtained in respect of the guinea-pig ileum by previous workers. The affinity constants, dissociation constants and the intrinsic activity values obtained for the cholinomimetics were the same in the two preparations and correspond to values previously reported by other workers. The sensitivity to ACh in the toad large intestine preparation was increased by physostigmine (0.36 x 10-5M) and compared favourably with results obtained by other workers using other biological preparations.
Conclusion: Isolated toad large intestine can be used as an inexpensive alternative to the guinea-pig ileum in the bioassay of cholinomimetics.
S A Igwe
Source of Support: None, Conflict of Interest: None