Identification of muscarinic receptor subtypes involved in catecholamine secretion in adrenal medullary chromaffin cells by genetic deletion

Abstract

BACKGROUND AND PURPOSEActivation of muscarinic receptors results in catecholamine secretion in adrenal chromaffin cells in many mammals, and muscarinic receptors partly mediate synaptic transmission from the splanchnic nerve, at least in guinea pigs. To elucidate the physiological functions of muscarinic receptors in chromaffin cells, it is necessary to identify the muscarinic receptor subtypes involved in excitation. EXPERIMENTAL APPROACHTo identify muscarinic receptors, pharmacological tools and strains of mice where one or several muscarinic receptor subtypes were genetically deleted were used. Cellular responses to muscarinic stimulation in isolated chromaffin cells were studied with the patch clamp technique and amperometry. KEY RESULTSMuscarinic M1, M4 and M5 receptors were immunologically detected in mouse chromaffin cells, and these receptors disappeared after the appropriate gene deletion. Mouse cells secreted catecholamines in response to muscarinic agonists, angiotensin II and a decrease in external pH. Genetic deletion of M1, but not M3, M4 or M5, receptors in mice abolished secretion in response to muscarine, but not to other stimuli. The muscarine-induced secretion was suppressed by MT7, a snake peptide toxin specific for M1 receptors. Similarly, muscarine failed to induce an inward current in the presence of MT7 in mouse and rat chromaffin cells. The binding affinity of VU0255035 for the inhibition of muscarine-induced currents agreed with that for the M1 receptor. CONCLUSIONS AND IMPLICATIONSBased upon the effects of genetic deletion of muscarinic receptors and MT7, it is concluded that the M1 receptor alone is responsible for muscarine-induced catecholamine secretion. AbbreviationsHA, haemagglutinin; IR, immunoreactivity; KO, knockout; nAChR, nicotinic ACh receptor BJP British Journal of Pharmacology

Alpha 7 nicotinic receptor coupling to heterotrimeric G proteins modulates RhoA activation, cytoskeletal motility, and structural growth

“…We examined the effect of mAChR activation on neurite growth using carbachol, which activates M1, M4, and M5 mAChRs endogenously expressed in PC12 cells (Berkeley and Levey ; Harada et al . ). Previous studies have shown that the Gαi coupled M4 mAChRs dominates in PC12 cells (Berkeley and Levey ).…”

Ca_v1.3 Channels as Key Regulators of Neuron-Like Firings and Catecholamine Release in Chromaffin Cells

“…Of particular interest in CC biology is the potential role of muscarinic receptors, whose activation causes prolonged membrane depolarizations, increased cell firing and sustained catecholamines release [4, 21]. The action is mediated by the M1 muscarinic receptor [132] and proceeds through the inhibition of TASK1-like channels [130]. As muscarine activates the PKC pathway in RCCs [4, 133], it is likely that Nav channels may undergo the well-known PKC-dependent down-regulation mediated by muscarinic receptors [134].…”

Molecular mechanism for muscarinic M1 receptor‐mediated endocytosis of TWIK‐related acid‐sensitive K+ 1 channels in rat adrenal medullary cells

“…; Harada et al . ). Briefly, rats were killed by cervical dislocation and the adrenal glands were taken out.…”

“…This muscarinic excitation in mouse AM cells was abolished by the genetic ablation of M 1 receptor (M 1 R) (Harada et al . ), and the muscarinic inhibition of TASK1 channels in rat and mouse AM cells was suppressed by MT7 (Harada et al . ), a specific M 1 R antagonist (Servent & Fruchart‐Gailard, ).…”

“…), and the muscarinic inhibition of TASK1 channels in rat and mouse AM cells was suppressed by MT7 (Harada et al . ), a specific M 1 R antagonist (Servent & Fruchart‐Gailard, ). These results indicate that M 1 R activation results in suppression of TASK1 channels in AM cells.…”