Modulation of high-voltage-activated Ca2+ channels by muscarinic receptor agonists was investigated in isolated parasympathetic neurons of neonatal rat intracardiac ganglia using the amphotericin B perforated-patch whole cell recording configuration of the patch-clamp technique. Focal application of the muscarinic agonists acetylcholine (ACh), muscarine, and oxotremorine-M to the voltage-clampe...

1. The effects of muscarinic receptor agonists on the electrically-evoked surface-negative field potential (N-wave) were measured in the guinea-pig olfactory cortex slice maintained in vitro. 2. Bath-superfusion of (+/-)-muscarine, acetylcholine (ACh), carbachol (CCh), or methacholine (MCh) (10-200 microM) produced reversible, dose-dependent depressions of the N-wave (ACh and MCh effects were o...

Under physiological circumstances, cellular responses often reflect integration of signaling by two or more different receptors activated coincidentally or sequentially. In addition to heterologous desensitization, there are examples in which receptor activation either reveals or potentiates signaling by a different receptor type, although this is perhaps less well explored. Here, we characteri...

Preincubation with receptor agonists or phorbol esters desensitized muscarinic-receptor-mediated [3H]cyclic GMP responses in mouse neuroblastoma N1E-115 cells. However, desensitization mediated by phorbol esters was heterologous, whereas that effected by receptor agonist was specific towards the muscarinic receptors. In addition, there was no loss of cell surface muscarinic receptors, as measur...

Acetylcholine and muscarinic agonists inhibit chemosensory activity in the rabbit carotid sinus nerve (CSN). Because the mechanism of this inhibition is poorly understood, we have investigated the kinetics and distribution of muscarinic receptors in the rabbit carotid body with the specific muscarinic antagonist [3H]quinuclidinylbenzilate ([3H]QNB). Equilibrium binding experiments identified di...

The chronotropic response of embryonic chick hearts to cholinergic agents is first clearly detectable on day 5 in ouo and full responsiveness develops by day 7. Muscarinic acetylcholine receptors in fully responsive 9day-old hearts specifically bind the muscarinic antagonist quinuclidinyl benzilate. Binding is blocked effectively by muscarinic agonists and antagonists but is poorly inhibited by...

One component of muscarinic receptor inhibition of the function of cardiac ventricles is mediated by the inhibition of activated adenylate cyclase activity in sarcolemma. We have shown previously that muscarinic agonists inhibit GTP- but not Gpp(NH)p-activated adenylate cyclase activity, and various studies in other tissues indicate that nonhydrolyzable GTP analogues prevent inactivation of the...

The chronotropic response of embryonic chick hearts to cholinergic agents is first clearly detectable on day 5 in ouo and full responsiveness develops by day 7. Muscarinic acetylcholine receptors in fully responsive 9day-old hearts specifically bind the muscarinic antagonist quinuclidinyl benzilate. Binding is blocked effectively by muscarinic agonists and antagonists but is poorly inhibited by...

In lampreys, reticulospinal neurons integrate sensory inputs to adapt their control onto the spinal locomotor networks. Whether and how sensory inputs to reticulospinal neurons are modulated remains to be determined. We showed recently that cholinergic inputs onto reticulospinal neurons play a key role in the initiation of locomotion elicited by stimulation of the mesencephalic locomotor region...

The purpose of the present study was to determine the effects of muscarinic cholinergic receptor antagonists and agonists on prepulse inhibition (PPI) of the acoustic startle reflex in rats. The muscarinic receptor antagonist scopolamine (0.03-1.0 mg/kg) produced a significant dose-dependent decrease in PPI without affecting startle amplitude. In contrast, N-methyl scopolamine, the quaternary a...