• The Korean Journal of Physiology and Pharmacology
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• v.8 no.3
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• pp.153-159
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• 2004

The interstitial cells of Cajal (ICCs) are the pacemaker cells in gastrointestinal tract and generate electrical rhythmicity in gastrointestinal muscles. Therefore, ICC may be modulated by endogenous agents such as neurotransmitter, hormones, and prostaglandins (PGs). In the present study, we investigated the effects of prostaglandins, especially $PGE_2$, on pacemaker currents in cultured ICCs from murine small intestine by using whole-cell patch clamp techniques. ICCs generated spontaneous slow waves under voltage-clamp conditions and showed a mean amplitude of $-452{\pm}39\;pA$ and frequency of $18{\pm}2$ cycles/min (n=6). Treatments of the cells with $PGE_2$ $(1\;{\mu}M)$ decreased both the frequency and amplitude of the pacemaker currents and increased the resting currents in the outward direction. $PGE_2$ had only inhibitory effects on pacemaker currents and this inhibitory effect was dose-dependent. For characterization of specific membrane EP receptor subtypes, involved in the effects of $PGE_2$ on pacemaker currents in ICCs, EP receptor agonists were used: Butaprost $(1\;{\mu}M)$, $EP_2$ receptor agonist, reduced the spontaneous inward current frequency and amplitude in cultured ICCs (n=5). However sulprostone $(1\;{\mu}M)$, a mixed $EP_1$ and $EP_3$ agonist, had no effects on the frequency, amplitude and resting currents of pacemaker currents (n=5). SQ-22536 (an inhibitor of adenylate cyclase; $100\;{\mu}M$) and ODQ (an inhibitor of guanylate cyclase; $100\;{\mu}M$) had no effects on $PGE_2$ actions of pacemaker currents. These observations indicate that $PGE_2$ alter directly the pacemaker currents in ICCs, and that the $PGE_2$ receptor subtypes involved are the $EP_2$ receptor, independent of cyclic AMP- and GMP-dependent pathway.

• YAKHAK HOEJI
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• v.36 no.3
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• pp.220-229
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• 1992

The muscarinic acetylcholine receptors of the dog unpregant uterus were characterized using $[^3H]quinuclidinyl$ benzilate(QNB) as a radioligand and the binding of muscarinic receptor agonists and antagonists in the uterus was compared to that in the urinary bladder which contains almost exclusively the M2 receptors in order to determine the receptor subtypes in the uterus. $[^3H]QNB$ binding to uterus and bladder was rapid, saturable and reversible. Scatchard analysis of the saturation data gave linear plots and the Hill coefficients were close to unit, which indicated that each preparation contained a single population of specific binding sites for $[^3H]QNB$. The KD values(120 pM) for QNB were almost identical in both organs, whereas the $B_{max}$ value of 256 fmol/mg protein in the uterus was significantly different from that of 563 fmol/mg protein in the bladder. Muscarinic agonists and antagonists inhibited in a competitive manner the $[^3H]QNB$ binding to the same extent in both organs. The competition binding studies using antagonists(atropine and pirenzepine) exhibited a single binding site and this site had a low affinity for pirenzepine with the Ki value of about 330 nM. However, high and low affinity binding sites were observed with carbachol, methacholine and oxotremorine. These binding studies with agonists and antagonists did not show any differences in drug affinities between uterus and bladder. These results indicate that the muscarinic receptors in the uterus are M2 receptors which have a low affinity for pirenzepine.

• Animal Bioscience
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• v.35 no.12
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• pp.1904-1910
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• 2022

Objective: This study aimed to investigate the effects of corticotropin-releasing factor (CRF) on the feed intake of broiler chickens and explore its influencing mechanism. Methods: The study included two trials. In trial 1, 32 male broiler chickens (Arbor Acres, Gallus gallus domesticus) were given ventricle buried tubes, and they were allowed to recover for 3 days. At 8:00 AM, intracerebroventricular (ICV) injection with CRF or normal saline was performed in 10-day-old broiler chickens, which were divided into the 5, 10, and 20 ㎍ and control (normal saline) groups according to the dose of CRF injection. In trial 2, chickens were divided into the 10 ㎍ and control group (physiological saline) to repeat trial 1. Results: Results of trial 1 showed that the cumulative amount of feed intake in the 10 or 20 ㎍ groups was considerably lower than that of the control group after ICV injection with CRF. The lowest amount of feed intake was obtained with the addition of 10 ㎍ of CRF. In trial 2, the expression of ghrelin in the hypothalamus injected with 10 ㎍ of CRF increased significantly, but the expression of ghrelin in various sections of the small intestine considerably decreased. The expression of CRF receptor subtypes 1 (CRFR1) in the hypothalamus and some parts of the small intestine remarkably increased, and the expression of CRF receptor subtypes 2 (CRFR2) increased only in the duodenum, whereas the expression of growth hormone secretagogue receptor (GHSR-1α) in the jejunum and ileum increased considerably after ICV injection of 10 ㎍ of CRF. Conclusion: The CRF at 10 ㎍ increased ghrelin expression in the hypothalamus and CRFR1 expression in the small intestine, and this phenomenon was related to the suppressed feed intake of broiler chickens.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1996.04a
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• pp.206-206
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• 1996

The C-terminus ends of the second putative transmembrane domains of both m1 and m2 muscarinic receptors contain a triplet of amino acid residues consisting of leucine (L), tyrosine (Y) and threonine (T), This triplet is repeated as LYT-LYT in m2 receptors at the interface between the second transmembrane domain and the first extracellular loop. Interestingly, however, it is repeated in a transposed fashion (LYT-TYL) in the sequence of m1 receptors. In this work we employed site-directed mutagenesis to investigate the possible significance of this unique sequence diversity for determining the distinct differential drug-receptor interaction and cellular function at m1 muscarinic receptor. Mutation of the LYTTYL sequence of m1 receptors to the corresponding m2 receptor LYTLYT sequence, however, did not result in a significant change in the binding affinity of the agonist carbachol or in the affinity of the majority of a series of receptor antagonists which are able to discriminate between wild-type m1 and m2 receptors. Surprisingly, the LYTLYT ml receptor mutant demonstrated markedly enhanced coupling to activation of phospholipase C without a change in its coupling to increased cyclic AMP formation. There was also an enhanced receptor sensitivity in transducing elevation of intracellular Ca$\^$2+/. These changes were not due to alterations in the rate of receptor. desensitization or sequestration, On the other hand, the reverse LYTLYT-LYTTYL mutation in the m2 receptor did not alter its coupling to inhibition of adenylate cyclase, but slightly enhanced its coupling to stimulation of PI hydrolysis, Our data suggest that the LYTTYL/LYTLYT sequence difference between ml and n12 muscarinic receptors is not involved in determining receptor pharmacology. On the other hand, while these differences might play a role in the modulation of muscarinic receptor coupling to PI hydrolysis, they are not important for specifying coupling of various subtypes of muscarinic receptors to different cellular signaling pathways.

• Biomolecules & Therapeutics
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• v.25 no.5
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• pp.471-481
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• 2017

The canonical transient receptor potential channels (TRPCs) constitute a series of nonselective cation channels with variable degrees of $Ca^{2+}$ selectivity. TRPCs consist of seven mammalian members, TRPC1, TRPC2, TRPC3, TRPC4, TRPC5, TRPC6, and TRPC7, which are further divided into four subtypes, TRPC1, TRPC2, TRPC4/5, and TRPC3/6/7. These channels take charge of various essential cell functions such as contraction, relaxation, proliferation, and dysfunction. This review, organized into seven main sections, will provide an overview of current knowledge about the underlying pathogenesis of TRPCs in cardio/cerebro-vascular diseases, including hypertension, pulmonary arterial hypertension, cardiac hypertrophy, atherosclerosis, arrhythmia, and cerebrovascular ischemia reperfusion injury. Collectively, TRPCs could become a group of drug targets with important physiological functions for the therapy of human cardio/cerebro-vascular diseases.

• Biomedical Science Letters
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• v.13 no.4
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• pp.333-339
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• 2007

Recently, much attention has been paid to human retinoblastoma since it provide a good model system for studying mechanisms underlying cell growth, differentiation, proliferation, and apoptosis, and for developing cancer therapy. However, until now it is unclear whether purinergic receptors are involved in the calcium mobilization in the retinoblastoma cells. In this regard, we measured possible purinergic signaling in WERI-Rb-1 cells using $Ca^{2+}$ imaging technique and RT-PCR method. ATP-induced $[Ca^{2+}]_i$ transients was maintained to about $90.7{\pm}1.0%$ of the control (n=48) even in the absence of extracellular calcium. The ATP-induced intracellular calcium response was only attained to $10.4{\pm}1.8%$ (n=55) of peak amplitude of the control after preincubation of 1 ${\mu}MU-73122$, a PLC inhibitor, but it was not affected by 1 ${\mu}MU-73343$, a inactive form of U-73122. And also ATP-induced $[Ca^{2+}]_i$ rise was almost attenuated by 20 ${\mu}M$ 2-APB, a putative $IP_3$ receptor inhibitor. Two subtypes of $IP_3$ receptor $(IP_{3-1}R,\;IP_{3-2}R)$ were identified by a RT-PCR method. These findings suggest that purinergic stimuli can cause calcium mobilization via $PLC-IP_3$ pathway after the activation of P2Y receptors in the retinoblastoma cells, which may play important roles in cell proliferation, differentiation, growth, and cell death.

• YAKHAK HOEJI
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• v.45 no.2
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• pp.205-213
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• 2001

The dopaminergic receptors were consisted of two distinct subtypes, $D_1$and $D_2$, each having different function. The present study was attempted to investigate the effects of R(-)-2,10,11-trihydroxy-N-n-propylnoraporphine (TNPA), a dopamine $D_2$receptor agonist, on renal function in dog. TNPA (5.0~15.0 $\mu$g/kg), when given into the vein, produced a dose-dependently antidiuresis along with the decrease in osmolar clearance ( $C_{osm}$) and urinary excretion of sodium and potassium ( $E_{Na}$ , and $E_{K}$). It also increased reabsorption rates of sodium and potassium in renal tubules ( $R_{Na}$ , $R_{K}$) without any changes in glomerular filtration rate (GFR), renal plasma flow (RPF) and free water clearance ( $C_{H2o}$). TNPA (0.5~1.5 $\mu$g/kg/min) infused into a renal artery decreased urine flow both in the experimental and the control kidneys. TNPA (1.5~5.0 $\mu$g/kg) administered via the carotid artery also greatly exhibited antidiuresis even at intravenously ineffective doses. Changes of renal function by TNPA given into both the renal artery and the carotid artery were almost the same aspect to those induced by intravenous TNPA. These results obtained from the present study suggest that TNPA produces antidiuresis by increasing the reabsorption rates of electrolytes in renal tubules, mainly distal tubule, through changing of central function.unction.

• Biomolecules & Therapeutics
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• v.7 no.3
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• pp.278-284
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• 1999

DK1001 is a thebain derivative, which is newly synthesized as an alkaloid analgesic. This study was designed to study effects of DK1001 on the ligands binding to the opioid receptor subtypes, and general pharmacology of DK1001. DK1001 inhibited the binding of [$^3H$]DAMGO, a selective mu-subtype agonist, to the opioid receptor of rat forebrain in a concentration-dependent manner. $EC_{50}$ of DK1001 was significantly lower than that of morphine. DK1001 inhibited the binding of 〔$^3$H〕DPDPE, a selective delta-subtype agonist concentration-dependently. DK1001(0.5 mg/kg) had no effects on behavior, body temperature, blood pressure. respiratory rate, and intestinal charcoal propulsion of mice. In addition, DK1001 did not affect on the contractilities of isolated muscle strips of aorta, ileum, and trachea of rats. These results suggest that DK1001 might be a potent analgesic without serious side effects.

• Animal cells and systems
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• v.1 no.3
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• pp.497-505
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• 1997

Dopamine plays diverse roles in the fetal brain development and differentiation. However, the development of the dopaminergic neurons and its receptors has not been fully understood. In our studies, in situ hybridization and immunohistochemical methods were used to investigate the ontogeny of dopaminergic neurons and its receptor subtypes during the fetal development of the rat. In situ hybridization data showed that dopamine $D_1$ and $D_2$ receptor mRNAs were expressed in the ventricular and subventricular zones of ganglionic eminence, thalamus, hypothalamus, and cortical neuroepithelium on gestational day 13. Expression of dopamine $D_1$ and $D_2$ receptors during gestational days 17 and 19 reached the same or similar level of that in the adult brain. Expression of $D_1$ receptor mRNA preceded that of $D_2$ receptor mRNA in the early developmental stage, although this pattern was reversed with the sharp increase of $D_2$ receptor mRNA soon after. $D_2$ receptor mRNA was expressed in substantia nigra of mesencephalon of the fetal rat brain. However, $D_1$ receptor mRNA was not detected in substantia nigra. Our results indicate that dopamine might function in the fetal brain during the early gestational period.

• Bulletin of the Korean Chemical Society
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• v.27 no.11
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• pp.1861-1864
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• 2006