The isolated cremaster muscle preparation and (external) spermatic nerve-cremaster muscle preparation of the guinea-pig.
The isolated cremaster muscle preparation and spermatic nerve-cremaster muscle preparation of the guinea-pig were studied in vitro to determine their suitability as pharmacological test models. The preparation was contracted by acetylcholine, carbachol, succinylcholine and decamethonium (pD2 values, 4-2, 5-3, 7-3 and 7-4, respectively) through an action on a curare-sensitive cholinoceptor. Lobeline and DMPP were ineffective. Nicotine contracted the muscle, but there was tachyphylaxis. Tubocurarine and hexamethonium presumably competitively antagonized acetylcholine (pA2 values, 7-3 and 5-8); lobeline was a non-competitive antagonist (pD'2 value, 6-4). Atropine and mecamylamine exerted a dualistic action against acetylcholine (final pD'2 values, 5-3 and 6-7, respectively). Tubocurarine, succinylcholine and decamethonium exhibited their typical action when tested with spermatic nerve-cremaster muscle preparation; the latter two drugs also produced muscle spasm. Hexamethonium was a weak blocker of neuromuscular transmission. Atropine, mecamylamine, lobeline and DMPP exhibited neuromuscular blocking activity; however, directly evoked muscle twitches were also notably affected. The cremaster muscle preparations seem to add usefully to the list of currently used in vitro tests, with the added advantage that a mammalian skeletal muscle model is used for simultaneous quantitative studies.
D000009:Abdominal Muscles; D000818:Animals; D004558:Electric Stimulation; D005837:Genitalia, Male / Q000294:innervation; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008959:Models, Neurological; D009132:Muscles / Q000502:physiology; D009469:Neuromuscular Junction / Q000187:drug effects; D010276:Parasympatholytics / Q000494:pharmacology; D010277:Parasympathomimetics / Q000494:pharmacology; D013997:Time Factors
D010276:Parasympatholytics; D010277:Parasympathomimetics