Effects of indole alkaloids from Gardneria nutans Sieb. et Zucc. and Uncaria rhynchophylla Miq. on a guinea pig urinary bladder preparation in situ.

Methyl-2-acetoxyethyl-2′-chloroethylamine (acetyicholine-mustard) isomerizes in aqueous solution to form a cyclic ion, N-methyl-N-(2-acetoxyethyl)aziridinium, which structurally resembles acetylcholine. It is a potent stimulant of the guinea pig ileum, being approximately one-sixth as potent as acetylcholine at pH 7.4 and one-third as potent at pH 8.4. The agonist activity is inhibited by atropine, by preincubation with acetylcholinesterase, and pretreatment with thiosulfate ion. Mepyramine does not inhibit the stimulant action.One hour exposures of ileum segments to concentrations of acetylcholine-mustard in excess of those producing maximal responses, followed by a 1 h recovery period, did not produce evidence of postsynaptic receptor alkylation. Post-treatment responses to acetylcholine were slightly depressed, but these reductions were not related to the incubation concentrations of the agonist haloalkylamine. Pilocarpine-induced responses were unaltered by this treatment whereas 5-hydroxytryptamine responses were slightly potentiated and histamine responses were slightly and inconsistently modified.These treatments produced persistent, dose-related increases in muscle tone, an effect consistent with accumulations of spontaneously liberated acetylcholine and possibly caused by inhibition of in situ acetylcholinesterase.Ostensibly, the evidence suggests that the acetylcholine-like aziridinium ion can stimulate, but not inhibit, the muscarinic receptors of the guinea pig ileum.

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Transport of 3H L-Alanine Across the Blood-Brain Barrier of in Situ Perfused Guinea Pig Brain

Biology and Physiology of the Blood-Brain Barrier - Advances in Behavioral Biology ◽

10.1007/978-1-4757-9489-2_7 ◽

1996 ◽

pp. 35-39

Author(s):

Ivanka D. Markovic ◽

Zoran B. Redzic ◽

Suzana S. Jovanovic ◽

Dusan M. Mitrovic ◽

Ljubisa M. Rakic

Keyword(s):

Guinea Pig ◽

Blood Brain Barrier ◽

Brain Barrier ◽

Blood Brain ◽

Pig Brain ◽

Guinea Pig Brain

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ANG II modifies cardiomyocyte function via extracardiac and intracardiac neurons: in situ and in vitro studies

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1997.272.3.r766 ◽

1997 ◽

Vol 272 (3) ◽

pp. R766-R775 ◽

Cited By ~ 6

Author(s):

M. Horackova ◽

J. A. Armour

Keyword(s):

Guinea Pig ◽

Receptor Antagonist ◽

Neuronal Activity ◽

Ang Ii ◽

Arterial Blood ◽

Cardiac Ganglia ◽

In Situ Experiments ◽

Anesthetized Dogs

To determine whether angiotensin II (ANG II) affects cardiac performance via neurons in intrathoracic cardiac ganglia, studies were performed on anesthetized dogs. To exclude possible vascular regulatory effects of ANG II, experiments were also performed using long-term cultures of adult guinea pig ventricular cardiomyocytes with or without intrathoracic neurons. 1) In in situ experiments in 10 anesthetized dogs, cardiac augmentation occurred when ANG II (10 microl or 0.1 ml; 10-100 microM) was administered into limited loci within acutely decentralized stellate or middle cervical ganglia that were neurally connected to, but not those disconnected from, the heart. In another 18 dogs, ANG II increased intrinsic cardiac neuronal activity when administered adjacent to such neurons or into their local arterial blood supply. Ventricular ionotropic effects elicited by ANG II were eliminated by timolol, whereas increases in intrinsic cardiac neuronal activity were not affected. Effects elicited by ANG II were eliminated by administration of a selective AT1 receptor antagonist (losartan) but not by a selective AT2 receptor antagonist (PD-123319). 2) In in vitro experiments, ANG II (100 nM) induced positive chronotropic effects on cultured adult guinea pig cardiomyocytes innervated with adult extrinsic or intrinsic cardiac neurons, but not those cultured without neurons. The frequency of calcium inward current (Ca(i)) transients (recorded by fura 2 fluorescence) increased in innervated cocultures but not in the noninnervated cardiomyocyte cultures; however, the amplitude of Ca(i) transients was not affected by ANG II in cultures or in freshly isolated adult guinea pig cardiomyocytes. ANG II-induced effects in cocultures were blocked by losartan but not PD-123319 or timolol. Thus 1) ANG II-sensitive neurons exist in intrathoracic extracardiac and intrinsic cardiac ganglia; 2) these neurons possess AT1 receptors; and 3) these neurons appear to act directly and indirectly via adrenergic neurons to enhance cardiomyocyte function.

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