ABSTRACT
Objective To investigate the effect of ethanol on level of the main hippocampal subtype of muscarinic receptor(M1)in mice,and evalu?ate whether the content change on this receptor could be linked with alterations in cognition,so as to further reveal the mechanism of brain damage in?duced by ethanol. Methods Sixty female mice were randomly divided into four groups. The model mice were induced by intragastric administration of ethanol at dose of 8%,16%,and 32%respectively of 0.2 mL/10 g for 8 weeks according to the protocol,and control group were treated with intra?gastric administration of distilled water. The capability of learning and memory were examined by Morris water maze,and ELISA method was used to measure the M1 receptor content in hippocampus in each group of mice. Results Compared with first day,the mean escape latency period on the fifth day was significantly shortened in each group. There was no significant difference between ethanol and control group for the mean escape latency period on the fifth day. Compared with the control group,the active time in the target quadrant was significantly shortened in 16%and 32%ethanol group. M1 receptor content in hippocampus formation was significantly decreased in all the ethanol group mice. The ethanol concentration was nega?tive correlated with the M1 receptor content. Conclusion Chronic alcoholism can induce the memory impairment in mice,which might be associat?ed with the low level of M1 receptor subtype in hippocampus of mice.
ABSTRACT
Cholinergic system in CNS is involved in learning and memory. Scopolamine as muscarinic acetylcholine receptor antagonist is used for creation of memory impairment. The purpose of this study is evaluation of scopolamine-based amnesia on memory retention and the effect of this phenomenon on the number of neurons contains M1-receptors in the male Wistar rats hippocampal regions. Thirty-five male Wistar rats (200+/-20 g) were distributed randomly into five groups. Control group (intact samples) and 3 experimental groups with sham group (saline) were tested by the method of passive avoidance (shuttle box) in doses of 0.2, 0.5 and 1 mg/kg (intraperitoneally) as a single dose. After one week, memory test was taken from the rats. Finally, brains dissected from sacrificed rats, and then processed tissues were stained with antibody against M1 receptors (Immunohistochemistry technique) followed by counting of hippocampal CA1, CA3 and DG regions. Our results showed significant decrease in neurons contains M1-receptors in all area of hippocampus. We found that the less number of M1-neurons showed in 1 mg/kg dose of scopolamine. We concluded that scopolamine as muscarinic acetylcholine receptor antagonist can reduce dose-dependently the density of M1-neurons in all areas of hippocampus.
El sistema colinérgico en el SNC está implicado en el aprendizaje y la memoria. La escopolamina como receptor antagonista de acetilcolina muscarínico es utilizada para la creación del deterioro de la memoria. El propósito de este estudio es la evaluación de la amnesia basada en escopolamina sobre la retención de memoria y el efecto de este fenómeno en la cantidad de neuronas en receptores M1 en regiones del hipocampo en ratas macho Wistar. Se distribuyeron al azar, 35 ratas macho Wistar (200+/-20 g) en cinco grupos. El grupo de control (muestras intactas) y 3 grupos experimentales con grupo de tratamiento simulado (solución salina) analizadas por método de evasión pasiva (caja de transporte) en dosis de 0,2; 0,5 y 1 mg/kg (por vía intraperitoneal) como dosis única. Al término de una semana se realizó prueba de memoria de las ratas. Por último, los cerebros diseccionados de las ratas sacrificadas y los tejidos procesados fueron teñidos con anticuerpos contra los receptores M1 (técnica inmunohistoquímica), seguido por el recuento de regiones CA1, CA3 y DG del hipocampo. Nuestros resultados mostraron una disminución significativa en las neuronas con receptores M1 en toda el área del hipocampo. Se encontró que el número menor de neuronas M1, y fue demostrado en 1 mg/kg de dosis de escopolamina. Llegamos a la conclusión de que la escopolamina como antagonista del receptor de acetilcolina muscarínico puede, dependiendo de la dosis, reducir la densidad de neuronas M1 en todas las áreas del hipocampo.
Subject(s)
Male , Animals , Rats , Muscarinic Antagonists/pharmacology , Scopolamine/pharmacology , Hippocampus , Memory , Receptor, Muscarinic M1/antagonists & inhibitors , Immunohistochemistry , Rats, WistarABSTRACT
AIM:To establish a screening model based on muscarinic receptor type 1(M1) for drugs against Alzheimer's disease (AD). METHOD: Human M1 receptor was expressed in HEK293 (human embryonic kidney) cells, and its activation was measured by the intracellular cAMP (cyclic AMP) level. Exogeneous 3H-cAMP was used to compete the intracellular cAMP binding sites. Acetylcholine chloride was used as a positive drug to ensure the sensitivity of this model. RESULT: HEK293 cell expressing system of human M1 receptor was established. Different concentrations of acetylcholine chloride (10-9～10-4 mol/L) activation of M1 receptor leads to an increase of intracellular cAMP 10.343×10-4～33.754×10-4 pmol/μl. CONCLUTION:This screening model has positive response to M1 receptor agonist and can be used for drug screening.
ABSTRACT
Aim To study the characteristics of KCNQ2/3 potassium channel expressed in CHO cells and its modulation by M_1 receptor.Methods KCNQ2 and KCNQ3 potassium channels and M_1 receptor were co-expressed in CHO cells.Whole cell patch-clamp techniques was used to observe the characteristics of KCNQ2/3 current,its modulation by the M_1 receptor,and the effects of the common potassium channel blockers.Results KCNQ2/3 current recorded in CHO cells was a slow-activation low-threshold non-inactivating,voltage-dependent outward potassium current.KCNQ2/3 current was elicited at about-60 mV,V_(1/2)(-26.8?1.2) mV and the deactivation current fitted two exponential function,with ?_(fast) of 101ms and ?_(slow) of 309 ms.The channel was not sensitive to common pharmacological blockers such as 4-AP,Ba~(2+) and TEA,but was inhibited significantly by linopirdine,with a IC_(50) of(6.5?0.83) ?mol?L~(-1).Acetylcholine suppressed the KCNQ2/3 current reversibly via M_1 receptor,with a IC_(50) of(0.7?0.05) ?mol?L~(-1).Conclusion KCNQ2 and KCNQ3 channels are the molecular basis of M-current observed in neuronal cells.KCNQ2/Q3 current expressed in CHO cells has similar characteristics as that seen in neuronal M-current.Linopirdine is a powerful blocker of KCNQ2/3 channel and acetylcholine inhibits the current by muscarinic M_1 receptor.This experiment has laid a solid basis for further study of M-current and KCNQ2/3 current,and is important for the study of neurological diseases relating to alteration of M-current,such as convulsion,epilepsy and Alzheimers disease.
ABSTRACT
AIM To observe the effects of ZMS and ZMR(isomer of ZMS),two active components of Zhimu on learning and memory ability and muscarinic subtype M 1 receptor density in aged rats. METHODS 24 month-old SD rats were randomly divided into aged control group, ZMS and ZMR treatment group. Young rats were used as normal control group. The learning and memory ability was detected by Y-maze method. The muscarinic subtype M 1 receptor density in the brain was detected by 3H-QNB binding tests. RESULTS It was found that daily oral administration of ZMS and ZMR for 40 d significantly enhanced the learning and memory ability and the muscarinic subtype M 1 receptor density in the brain of the aged rats. CONCLUSION These results suggested that ZMS and ZMR probably have potential preventive and curative action for the progressive deterioration of the cholinergic system in Alzheimers disease (AD).