Biomaterial Database

Mechanisms underlying spontaneous phasic contractions and sympathetic control of smooth muscle in the rat caudal epididymis. 2021

Retsu Mitsui, and Hikaru Hashitani, and Richard J Lang, and Dirk F van Helden

Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.

Here we investigate mechanisms underlying spontaneous phasic contractions (SPCs) and sympathetic control of contractility in the rat epididymis, a long tubular duct involved in transportation and maturation of sperm. Longitudinal contractions of short segments (~ 1.5 mm) of rat proximal and distal caudal epididymal duct were measured + / - nerve stimulation. The extent of sympathetic innervation of these duct regions was determined by immunohistochemistry. Proximal caudal duct segments (150-300 μm dia.) exhibited SPCs, while distal segments (350-500 μm) were quiescent in ~ 80% of preparations. SPC amplitude and frequency were reduced by the L-type voltage-dependent Ca2+ channel (LVDCC) blocker nifedipine (1 μM), with the T-type voltage-dependent Ca2+ channel (TVDCC) blocker ML218 (1 μM) specifically decreasing SPC frequency. SPCs were inhibited upon blockade of the SR/ER Ca2+-ATPase (CPA 10 μM). SPCs were also inhibited by caffeine (1 μM), 2-APB (100 μM), niflumic acid (100 μM), or by lowering extracellular [Cl-] from 134.4 to 12.4 mM but not by ryanodine (25 μM) or tetracaine (100 μM). Electrical field stimulation (EFS) at 2 Hz for 60 s caused a sustained α1-adrenoceptor-sensitive contraction in distal segments and enhanced and/or induced α2-adrenoceptor-sensitive oscillatory phasic contractions in proximal and distal segments, the latter mimicked by application of the α2-adrenoceptor agonist clonidine. We hypothesise that SPCs in the proximal cauda are triggered by pacemaker mechanisms involving rhythmic IP3 receptor-operated SR/ER store Ca2+ release and resultant activation of CaCC with TVDCCs and possibly LVDCCs subserving in this process. Sympathetic nerve-released noradrenaline induces α2-adrenoceptor-mediated phasic contractions in the proximal and distal cauda. These findings provide new pharmacological targets for male infertility and contraception.

UI	MeSH Term	Description	Entries
D008297	Male		Males
D009119	Muscle Contraction	A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.	Inotropism,Muscular Contraction,Contraction, Muscle,Contraction, Muscular,Contractions, Muscle,Contractions, Muscular,Inotropisms,Muscle Contractions,Muscular Contractions
D009130	Muscle, Smooth	Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. (From Stedman, 25th ed)	Muscle, Involuntary,Smooth Muscle,Involuntary Muscle,Involuntary Muscles,Muscles, Involuntary,Muscles, Smooth,Smooth Muscles
D009543	Nifedipine	A potent vasodilator agent with calcium antagonistic action. It is a useful anti-anginal agent that also lowers blood pressure.	Adalat,BAY-a-1040,Bay-1040,Cordipin,Cordipine,Corinfar,Fenigidin,Korinfar,Nifangin,Nifedipine Monohydrochloride,Nifedipine-GTIS,Procardia,Procardia XL,Vascard,BAY a 1040,BAYa1040,Bay 1040,Bay1040,Monohydrochloride, Nifedipine,Nifedipine GTIS
D009638	Norepinephrine	Precursor of epinephrine that is secreted by the ADRENAL MEDULLA and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers, and of the diffuse projection system in the brain that arises from the LOCUS CERULEUS. It is also found in plants and is used pharmacologically as a sympathomimetic.	Levarterenol,Levonorepinephrine,Noradrenaline,Arterenol,Levonor,Levophed,Levophed Bitartrate,Noradrenaline Bitartrate,Noradrénaline tartrate renaudin,Norepinephrin d-Tartrate (1:1),Norepinephrine Bitartrate,Norepinephrine Hydrochloride,Norepinephrine Hydrochloride, (+)-Isomer,Norepinephrine Hydrochloride, (+,-)-Isomer,Norepinephrine d-Tartrate (1:1),Norepinephrine l-Tartrate (1:1),Norepinephrine l-Tartrate (1:1), (+,-)-Isomer,Norepinephrine l-Tartrate (1:1), Monohydrate,Norepinephrine l-Tartrate (1:1), Monohydrate, (+)-Isomer,Norepinephrine l-Tartrate (1:2),Norepinephrine l-Tartrate, (+)-Isomer,Norepinephrine, (+)-Isomer,Norepinephrine, (+,-)-Isomer
D010656	Phenylephrine	An alpha-1 adrenergic agonist used as a mydriatic, nasal decongestant, and cardiotonic agent.	(R)-3-Hydroxy-alpha-((methylamino)methyl)benzenemethanol,Metaoxedrin,Metasympatol,Mezaton,Neo-Synephrine,Neosynephrine,Phenylephrine Hydrochloride,Phenylephrine Tannate,Neo Synephrine,Tannate, Phenylephrine
D002121	Calcium Channel Blockers	A class of drugs that act by selective inhibition of calcium influx through cellular membranes.	Calcium Antagonists, Exogenous,Calcium Blockaders, Exogenous,Calcium Channel Antagonist,Calcium Channel Blocker,Calcium Channel Blocking Drug,Calcium Inhibitors, Exogenous,Channel Blockers, Calcium,Exogenous Calcium Blockader,Exogenous Calcium Inhibitor,Calcium Channel Antagonists,Calcium Channel Blocking Drugs,Exogenous Calcium Antagonists,Exogenous Calcium Blockaders,Exogenous Calcium Inhibitors,Antagonist, Calcium Channel,Antagonists, Calcium Channel,Antagonists, Exogenous Calcium,Blockader, Exogenous Calcium,Blocker, Calcium Channel,Blockers, Calcium Channel,Calcium Blockader, Exogenous,Calcium Inhibitor, Exogenous,Channel Antagonist, Calcium,Channel Blocker, Calcium,Inhibitor, Exogenous Calcium
D004822	Epididymis	The convoluted cordlike structure attached to the posterior of the TESTIS. Epididymis consists of the head (caput), the body (corpus), and the tail (cauda). A network of ducts leaving the testis joins into a common epididymal tubule proper which provides the transport, storage, and maturation of SPERMATOZOA.
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D012433	Ryanodine	A methylpyrrole-carboxylate from RYANIA that disrupts the RYANODINE RECEPTOR CALCIUM RELEASE CHANNEL to modify CALCIUM release from SARCOPLASMIC RETICULUM resulting in alteration of MUSCLE CONTRACTION. It was previously used in INSECTICIDES. It is used experimentally in conjunction with THAPSIGARGIN and other inhibitors of CALCIUM ATPASE uptake of calcium into SARCOPLASMIC RETICULUM.