Effect of thiopental sodium and barbitone sodium on the total acetylcholine content and acetylcholinesterase activity in the brain tissue of Arvicanthis niloticus

The total ACh content and AChE activity were determined 1 hr after the i.p. injection of different doses of thiopental sodium (5, 10 and 20 mg/ml/100 g body wt) and barbitone sodium (20, 40 and 80 mg/ml/100 g body wt). The effect of different time intervals (1 min, 10 min, 30 min, 1 hr, 2.5 hr, 5 hr, 8 hr, 12 hr, 24 hr and 48 hr) on the total ACh content and AChE activity was investigated after i.p. injection of 10 mg thiopental sodium and 40 mg barbitone sodium/ml/100 g body wt. Both thiopental sodium and barbitone sodium increased the total ACh content in the brain tissue of Arvicanthis niloticus. Both drugs inhibited the brain AChE activity. It is thought that the increase in the total ACh content in the brain tissue of Arvicanthis niloticus may be due to a decrease in the release of ACh from the neuronal tissue and a decrease in AChE activity.     

Effect of barbitone sodium and thiopental sodium on brain dopamine, noradrenaline, serotonin and 5-hydroxyindoleacetic acid content in Arvicanthis niloticus

The quantitative estimation of total dopamine (DA), noradrenaline (NE), serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) content in the whole brain tissue of normal Nile grass rat, Arvicanthis niloticus, gives and average of 631 +/- 12 ng DA/g, 366 +/- 12 ng NE/g, 617 +/- 15 ng 5-HT/g and 431 +/- 10 ng 5-HIAA/g fresh brain tissue. The effect of barbitone sodium and thiopental sodium on the total DA, NE, 5-HT and 5-HIAA content in the brain tissue of the Nile grass rat, Arvicanthis niloticus, was studied. The total DA, NE, 5-HT and 5-HIAA contents were determined 5 hr after i.p. injection of different doses of barbitone sodium (20, 40 and 80 mg/ml/100 g body wt) and thiopental sodium (5, 10 and 20 mg/ml/100 g body wt). The effect of different time intervals (1, 10, 30 min, 1, 2.5, 5, 8, 16, 24 and 48 hr) on the total brain DA, NE, 5-HT and 5-HIAA content was investigated after i.p. injection of 40 mg of barbitone sodium and 10 mg of thiopental sodium/ml/100 g body wt. Both barbitone sodium and thiopental sodium caused an increase in DA, NE and 5-HT content and a decrease in 5-HIAA content in the brain tissue of Arvicanthis niloticus. The increase in the whole brain contents of DA, NE and 5-HT after the administration of barbitone sodium and thiopental sodium may be due either to inhibition of transmitter release by an action at the monoamine nerve terminal or to effects causing a decrease in nerve impulse flow. On the other hand, the decrease in 5-HIAA may be due to the decrease in the turnover of 5-HT.     

Regional brain acetylcholine kinetics: effects of reserpine.

Regional brain acetylcholine (ACh) utilization was estimated from the rate of decline in ACh content following intracerebroventricular injection of hemicholinum-3 (HC-3, 20 μg). Rats were killed by microwave irradiation at various time intervals after HC-3 injection and ACh levels measured by radioimmunoassay. ACh content declined exponentially in all brain areas, with maximum depletion occurring within 30–60 min. The relative order of cholinergic activity in the regions studied was: hippocampus striatum hypothalamus pons-medulla. Endogenous ACh content was reduced by 13–18% in all regions 24 h after injection of reserpine (5 mg/kg, i.p.). Reserpine did not alter either the utilization rates nor the extent of HC-3-induced depletion of ACh. These results indicate a general effect of reserpine on the functional storage capacity of brain ACh.     

Circadian rhythmicity in the nervous system of the cockroach, Periplaneta americana

Diurnal rhythmicity of nervous activity in Periplaneta americana was investigated, using acetylcholine (ACh) content, acetylcholinesterase (AChE) and spontaneous electrical activities as indices. AChE and electrical activities were maximum at 0 hr and minimum at 12 hr, while ACh showed an opposite rhythm. Central nervous system extract from cockroaches at 12 hr elevated the electrical activity while 0 hr-extract exerted inhibition. Lower concentrations of ACh had an elevatory influence while higher concentrations inhibited the electrical activity. A hypothesis is proposed, suggesting synthetic and releasing phases of ACh in a regular diurnal cycle, to explain the results obtained.     

Effects of varying doses of methionine sulfoximine on liver glutamine synthetase activity and time courses of blood and urinary nitrogenous compounds in the chicken (Gallus domesticus)

1. The activity of liver glutamine synthetase was inhibited to 7-12% of the control activity by an intracardiac injection with methionine sulfoximine (MSM) at dosages of 20, 50, 75 and 100 mg/kg body wt. 2. Plasma glutamine concentrations in all the MSM treatments decreased sharply, then reached steady-state levels within 0.5-2.5 hr, which were almost proportional to a dose of MSM. 3. Blood ammonia concentration sharply increased to a steady-state level attained at 4.5 hr, which was proportional to a dose of MSM. The excretion rate of urinary ammonia augmented linearly up to the dose dependent maximum rates within 2-5 hr. 4. Plasma uric acid concentration dropped linearly by about 6.4 mg/100 ml at doses of 50, 75 and 100 mg MSM and by 3.7 mg/100 ml at a dose of 20 mg MSM within 2.5 hr, then recovered a little. 5. The decreases in excretion rates of urinary uric acid for the first 4 hr were almost the same at doses of 50 mg and larger, being twice as large as that of the control chicken. 6. Any doses of MSM affected neither the time course of excretion rate of total urinary nitrogen nor its total amounts for 7 hr after MSM treatment.     

Effect of dimethyl sulphoxide on mitochondrial biogenesis in regenerating rat liver and Saccharomyces cerevisiae

Effect of dimethyl sulphoxide (DMSO) on mitochondrial biogenesis in regenerating rat liver and cells of Saccharomyces cerevisiae during aerobiosis has been studied by monitoring the cytochrome oxidase activity. A single dose of DMSO (275 mg/100-125 g body wt) to normal rats stimulated cytochrome oxidase activity in liver mitochondria while the same dose to partial hepatectomized rats inhibited the enzyme activity. Administration of low dose of DMSO (92 mg/100-125 g body wt) to partial hepatectomized rats did not alter the enzyme activity. Anaerobic cells of S. cerevisiae on aerobiosis for 2 hr attained cytochrome oxidase activity level on par with aerobic cells. Inclusion of DMSO (275 mg/100 ml) in the growth medium of S. cerevisiae during respiratory adaptation exerted partial inhibitory effect on the formation of cytochrome oxidase at 2 hr period, while the 10-fold concentration inhibited the enzyme formation completely. However, the inhibitory effect of DMSO on enzyme formation was abolished on prolonged growth (18 hr and above), while these doses had no influence on cytochrome oxidase in aerobic cells of S. cerevisiae. The results imply that DMSO may be exerting its effect on the assembly of subunits into active enzyme complex during mitochondrial biogenesis.     

Effects of intravenous injection of butyrate on the exocrine pancreatic secretion in guinea pigs

1. The stimulus-secretion coupling in the pancreatic exocrine responses to i.v. injection of sodium butyrate was investigated in guinea pigs in vivo and in vitro. 2. Intravenous single injection of sodium butyrate (12.5-100 mumol/100 g body wt) caused an increase in fluid and amylase secretion in a dose-dependent manner. The responses evoked by sodium butyrate (100 mumol/100 g body wt) were not affected by prior injection of atropine (0.14 mumol/100 g body wt) or hexamethonium (4 mumol/100 g body wt). 3. The chloride concentration in secreted fluid increased slightly with an increase in flow rate in response to sodium butyrate, but decreased in response to secretin. 4. The amylase release from the pancreatic segments evoked by sodium butyrate (10(-6)-10(-2) M) increased dose-dependently. The responses were potentiated in the presence of secretin (1 C.H.R.u./ml), but were suppressed in the presence of acetylcholine (10(-6) M) or in a Ca-free solution containing EGTA (10(-4) M). 5. These results suggest that the secretory effects in response to i.v. injection of sodium butyrate probably arise from direct action on the acinar cells, and that an increase in cellular calcium concentration might be an important step in the secretion process, in guinea pig exocrine pancreas.     

Effect of envenomation on enzymes of brain of albino rats

Effects of high doses of cobra venom, (150 micrograms/120 +/- 20 g body wt) and viper venom (300 micrograms/120 +/- 20 g body wt) on aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), acetylcholinesterase (ACh) and alkaline phosphatase (ALP) of brain of albino rats were studied. While AST, LDH, ACh and ALP activities increased in both viper and cobra venom treated rats, ALT decreased in both groups compared to control.     

Toxic effects of garlic extract and garlic oil in rats

Significant rise in urea and D-aspartate aminotransferase and inhibition of alkaline phosphatase in serum were observed in rats fed garlic extract (2 ml/100 g body wt, intragastrically) for 10 days. The liver showed histological changes. Garlic oil feeding (10 mg/100 g body wt, intragastrically) after 24 hr fasting was found lethal. The cause of death appears to be acute pulmonary oedema. On histological examination, all the organs of the dead rats revealed severe congestion. However, similar feeding of garlic oil was well tolerated by rats in the fed state. Also, 24 hr fasted rats could tolerate this dose of garlic oil, provided they were previously adapted to garlic oil feeding.     

Hyponatremia-induced brain edema in guinea pigs is reduced by treatment with the novel anion transport inhibitor L-644,711

Cerebral edema in various disease states may result from astroglial swelling due to increased NaCl uptake mediated by enhanced Cl-HC03 exchange. We evaluated this mechanism in the pathogenesis of cerebral edema in acute hyponatremia by administering L-644,711, a fluorenyloxyacetate derivative that functions as an anion exchange inhibitor, to guinea pigs with severe reductions in serum Na+ concentration. Acute hyponatremia was induced for 54 hr by daily injections of arginine vasopressin (10 U/day) and 5% dextrose in water (7.5% body wt/day). Experimental animals received L-644,711, 20 mg/kg/day, while controls were given an equal volume of the diluent. This regimen lowered the serum Na from normal levels to 108 +/- 3 and 109 +/- 4 mM in experimental and control animals, respectively. Drug treatment resulted in less cerebral edema characterized by a reduction in brain total tissue water 432 +/- 4 vs 466 +/- 8 ml/100 g dry wt experimental vs control, P less than 0.005. This difference was composed mainly of less expansion of the intracellular water space, 287 +/- 11 vs 323 +/- 9 ml/100 g dry wt experimental vs control, p less than 0.005. The cerebral cortical Na+ +Cl content was reduced from 55.5 +/- 1.3 (control) to 39.5 +/- 1.1 mEq/100 g dry wt (experimental), p less than 0.01. These results indicate that treatment of guinea pigs with L-644,711 decreases brain NaCl content and attenuates cerebral edema during severe acute hyponatremia without normalizing the serum Na+ concentration.     

Phylogeny and historical demography of economically important rodents of the genus Arvicanthis (Mammalia: Muridae) from the Nile Valley: of mice and men

The present study clarified the taxonomy, phylogeny and historical demography of semicommensal Nile rats ( Arvicanthis ) from the Nile Valley in Sudan. Nile rats are important crop pests and zoonotic disease reservoirs and are closely associated with agricultural settlements in the Nile Valley. Phylogenetic analysis of the complete cytochrome b gene (1140 bp) of 23 individuals from six localities in Sudan (from two previously recognized species, Arvicanthis niloticus and Arvicanthis testicularis ), supported the existence of only a single species, A. niloticus , from the Nile Valley. Historical demography of the Sudanese Nile Valley population inferred from mismatch coefficients indicated that an exponential population expansion event occurred approximately 144 000–288 000 years ago, corresponding in time with early human expansion and colonization from Africa to the Middle East, Europe, and the world. The inferred high level of gene flow and large size of Sudanese Nile populations of A. niloticus is consistent with historically recent (300 years ago) exponential human population growth and intense agricultural activity inferred from archaeological and historical evidence. Two African Arvicanthis clades were well supported by the broader phylogenetic analysis: (1) A. niloticus , Arvicanthis abyssinicus and Arvicanthis neumanni and (2) Arvicanthis rufinus and Arvicanthis ansorgei from western Africa. Within the first clade, divergence between lineages of A. niloticus s.s. from west and north-east Africa (8.9%) suggests specific recognition, but sampling of geographically intermediate localities is required. Based on hypothesized palaeodrainage and palaeoclimatic patterns, we propose a simple model for speciation of Arvicanthis in Africa.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 641–655.     

The effects of adrenaline, reserpine, and atropine on acetylcholine content of the brain and peripheral ganglia in stress.

The effects of adrenaline, reserpine and atropine on ACh content in the cerebral cortex and brain stem and in the gastric tissues were investigated in the rats at rest and during stress induced by forced swimming. Adrenaline administered intraperitoneally twice at an interval of two hours in doses of 0.1 mg/kg and then subcutaneously in a dose 0.5 mg/kg increased acetylcholine content in the cerebral cortex of resting and in the gastric tissues of resting and swimming rats. Reserpine in doses of 3 mg/kg given 48, 24 and 7 hours before the experiment caused a significant rise in ACh content in the cerebral cortex of resting rats and in the brain stem during stress. Atropine given in a dose of 6 mg/kg at 8 h intervals during 2 days caused a significant fall in ACh level in the cerebral cortex and brain stem of resting rats, in the cortex of swimming animals, as well as a considerable rise in the gastric tissues of swimming rats.     

The rate of breakdown of methyl methanesulphonate, dimethyl sulphate and N-methyl-N-nitrosourea in the rat

1. The rates of decomposition of methyl methanesulphonate, dimethyl sulphate and N-methyl-N-nitrosourea in the rat were measured. 2. Dimethyl sulphate is no longer detectable in the blood of the rat 3min. after an intravenous dose (75mg./kg. body wt.). Methyl methanesulphonate is only just detectable in the blood 1(1/2)hr. after an intravenous dose (100mg./kg. body wt.). N-Methyl-N-nitrosourea is no longer detectable in the blood 15min. after an intravenous dose (100mg./kg. body wt.). 3. The exhalation of (14)CO(2) after an intragastric dose of N[(14)C]-methyl-N-nitrosourea (100mg./kg. body wt.) is appreciably slower than after an intravenous dose, from which it is estimated that the lifetime in the rat is 2-3hr.     

CHOLINESTERASE ACTIVITY OF NODAL AND INTERNODAL REGIONS OF MYELINATED NERVE FIBERS OF FROG

The distribution of cholinesterase (Ch-esterase) in isolated myelinated fibers of the frog has been investigated. Quantitative microgasometric measurements have confirmed the previous histochemical observations. Both approaches indicate that in frog nerve fibers acetylcholinesterase (ACh-esterase) is the only or the predominant enzyme when selective inhibitors and different substrates are used: acetylcholine (ACh), butyrylcholine, and acetyl-B-methylcholine (Mecholyl). By means of the microgasometric technique, a significant difference in ACh-esterase activity between axons isolated from ventral (37.2 ± 1.7 µmole x 10^-5 ACh/mm²/hr) and dorsal roots (2.0 ± 0.9 µmole x 10^-5 ACh/mm²/hr) was found. In the region of the node of Ranvier the enzyme activity (50.4 ± 4.4 µmole x 10^-5 ACh/mm²/hr) appears to be considerably higher than in the internodal area (36.6 ± 2.1 µmole x 10^-5 ACh/mm²/hr). The findings are discussed in relation to the theory of saltatory conduction and the ACh system.     

Acetylcholine release from the carotid body by hypoxia: evidence for the involvement of autoinhibitory receptors.

The purpose of the present study was to investigate whether hypoxia influences acetylcholine (ACh) release from the rabbit carotid body and, if so, to determine the mechanism(s) associated with this response. ACh is expressed in the rabbit carotid body (5.6 +/- 1.3 pmol/carotid body) as evidenced by electrochemical analysis. Immunocytochemical analysis of the primary cultures of the carotid body with antibody specific to ACh further showed that ACh-like immunoreactivity is localized to many glomus cells. The effect of hypoxia on ACh release was examined in ex vivo carotid bodies harvested from anesthetized rabbits. The basal release of ACh during normoxia ( approximately 150 Torr) averaged 5.9 +/- 0.5 fmol.min-1.carotid body-1. Lowering the Po2 to 90 and 20 Torr progressively decreased ACh release by approximately 15 and approximately 68%, respectively. ACh release returned to the basal value on reoxygenation. Simultaneous monitoring of dopamine showed a sixfold increase in dopamine release during hypoxia. Hypercapnia (21% O2 + 10% CO2) as well as high K+ (100 mM) facilitated ACh release from the carotid body, suggesting that hypoxia-induced inhibition of ACh release is not due to deterioration of the carotid body. Hypoxia had no significant effect on acetylcholinesterase activity in the medium, implying that increased hydrolysis of ACh does not account for hypoxia-induced inhibition of ACh release. In the presence of either atropine (10 microM) or domperidone (10 microM), hypoxia stimulated ACh release. These results demonstrate that glomus cells of the rabbit carotid body express ACh and that hypoxia overall inhibits ACh release via activation of muscarinic and dopaminergic autoinhibitory receptors in the carotid body.     

Effects of Exogenous Selenium on Nicotine-Induced Oxidative Stress in Rats

The effect of two different doses of selenium [1 and 50 μg selenium/100 g body weight (wt)] on nicotine-induced oxidative damage in liver was investigated in experimental rats. Male albino rats were maintained for 60 days as follows: (1) control group (normal diet), (2) nicotine group (0.6 mg/kg body wt)/day, (3) high-dose selenium (50 μg/100 g body wt)/day, (4) high-dose selenium (50 μg/100 g body wt) + nicotine (0.6 mg/kg body wt)/day, (5) low-dose selenium (1 μg/100 g body wt)/day, and (6) low-dose selenium (1 μg/100 g body wt) + nicotine (0.6 mg/kg body wt)/day. Nicotine administration caused a decrease in the activity of antioxidant enzymes, an increase in the concentration of lipid peroxidation products and protein carbonyls and an increase in the activity of nitric oxide synthase compared to the control group. Coadministration of nicotine and selenium reduced the concentration of lipid peroxidation products and increased the activity of antioxidant enzymes compared to the nicotine group. Selenium also enhanced the metabolism of nicotine. The antioxidant effect was more significant in the group administered a low dose of selenium.     

Zea mays L. extracts modify glomerular function and potassium urinary excretion in conscious rats

Diuretic and uricosuric properties have traditionally been attributed to corn silk, stigma/style of Zea mays L. Although the diuretic effect was confirmed, studies of the plant's effects on renal function or solute excretion were lacking. Thus, we studied the effects of corn silk aqueous extract on the urinary excretion of water, Na+, K+, and uric acid. Glomerular and proximal tubular function and Na+ tubular handling were also studied. Conscious, unrestrained adult male rats were housed in individual metabolic cages (IMC) with continuous urine collection for 5 and 3 h, following two protocols. The effects of 25, 50, 200, 350, and 500 mg/kg body wt. corn silk extract on urine volume plus Na+ and K+ excretions were studied in water-loaded conscious rats (2.5 ml/100 g body wt.) in the IMC for 5 h (Protocol 1). Kaliuresis was observed with doses of 350 (100.42 +/- 22.32-120.28 +/- 19.70 microEq/5 h/100 g body wt.; n = 13) and 500 mg/kg body wt. (94.97+/- 29.30-134.32 +/- 39.98 microEq/5h/100 g body wt.; n = 12; p<0.01), and the latter dose resulted in diuresis as well (1.98 +/- 0.44-2.41 +/- 0.41 ml/5 h/100 g body wt.; n = 12; p<0.05). The effects of a 500 mg/kg body wt. dose of corn silk extract on urine volume, Na+, K+ and uric acid excretions, and glomerular and proximal tubular function, were measured respectively by creatinine (Cler) and Li+ (ClLi) clearances and Na+ tubular handling, in water-loaded rats (5 ml/100 g body wt.) in the IMC for 3 h (Protocol 2). Clcr (294.6 +/- 73.2, n = 12, to 241.7 +/- 48.0 microl/ min/100 g body wt.; n = 13; p<0.05) and the Na+ filtered load (41.9 +/- 10.3, n = 12, to 34.3 +/- .8, n = 13, p<0.05) decreased and ClLi and Na+ excretion were unchanged, while K+ excretion (0.1044 +/- 0.0458, n=12, to 0.2289 +/- 0.0583 microEq/min/100 body wt.; n = 13; p<0.001) increased. For Na+ tubular handling, the fractional proximal tubular reabsorption (91.5 +/- 3.5, n = 12, to 87.5 +/- 3.4%; n = 13; p<0.01) decreased, and both fractional distal reabsorptions--I and II--increased (96.5 +/- 1.5, n = 12, to 97.8 +/- 0.9%; n = 13; p<0.01; and 8.2 +/- 3.5, n = 12, to 12.2 +/- 3.4%, n = 13, p<0.01, respectively). To summarize, in water-loaded conscious rats (2.5 ml/100 body wt.), corn silk aqueous extract is diuretic at a dose of 500 mg/kg body wt. and kaliuretic at doses of 350 and 500 mg/kg body wt. In water-loaded conscious rats (5.0 ml/100 g body wt.), corn silk aqueous extract is kaliuretic at a dose of 500 mg/kg body wt., but glomerular filtration and filtered load decrease without affecting proximal tubular function, Na+, or uric acid excretion.     

Metabolic control mechanisms in mammalian systems. Hormonal regulation of phosphofructokinase in the rat prostate and seminal vesicles

1. The hormonal regulation of phosphofructokinase was investigated in the accessory reproductive organs of the orchidectomized rat. 2. Phosphofructokinase activities declined to 51% and 47% in the prostate and 9% and 6% of the normal values in seminal vesicles 4 and 8 weeks after castration respectively. Administration of testosterone (100mug./100g. body wt.) for 3 days reversed substantially the effects of orchidectomy, and phosphofructokinase activity increased to 173% in the prostate and 536% in seminal vesicles as compared with the values of castrated controls. 3. Time-course studies demonstrated that after a single injection of testosterone (5mg./100g. body wt.) phosphofructokinase activity was maximally elevated to 236% in the prostate and 342% in seminal vesicles at 24hr. 4. Dose-response studies revealed that 2.5mg. of testosterone propionate/100g. body wt. was the minimal amount necessary to induce significant increases in enzyme activity in both accessory sex organs; maximal increases were obtained with a dose of 5mg./100g. body wt. 5. The observed enzyme increases induced by testosterone were inhibited by the simultaneous administration of oestradiol-17beta, and phosphofructokinase activity in this group of rats remained at 97% in the prostate and 137% of the control values in seminal vesicles. Oestradiol-17beta by itself failed to produce any significant effect on enzyme activity in either of these secondary sexual tissues. 6. The nature of the testosterone-induced increases in phosphofructokinase activity was studied by using a variety of inhibitors of RNA and protein synthesis. Cycloheximide, 5-fluorouracil and ethionine largely blocked the androgen-stimulated rise in enzyme activity observed 24hr. after steroid injection. The inhibitory effect of ethionine was completely reversed by the simultaneous administration of methionine. 7. Actinomycin, which is known to inhibit the synthesis of messenger RNA as well as the synthesis of other cellular RNA fractions, when given simultaneously with the hormone, also inhibited the testosterone-induced increases in prostatic and seminal-vesicular phosphofructokinase. However, when the antibiotic was given 6 or 12hr. after injection of the steroid, practically no inhibition of phosphofructokinase induction was obtained. This indicates that, once the enzyme-forming machinery is turned on and allowed to operate for a few hours, actinomycin is incapable of reversing the hormone-induced enzyme responses. 8. The results presented suggest that new RNA and protein synthesis may be involved in the observed androgen-induced increases in phosphofructokinase activity in the prostate and seminal vesicles of the orchidectomized rat.     

Contribution of the fluid phase endocytosis to bile flow in cholestasis and choleresis in rats

Using a single iv injection of 1 mg Evans blue dye/100 g body wt in rats, the contribution of the fluid phase endocytosis to bile flow was estimated. In control rats, this pathway contributed 2-4% of the bile flow or 10-20 microliter/hr/100 g body wt. This contribution was not affected by cholestasis induced by taurolithocholic acid or bile duct obstruction or by choleresis induced by dehydrocholic acid. It is concluded that fluid phase endocytosis does not significantly influence bile formation but, rather, may be implicated in the remodeling of liver cell plasma membranes.     

Sensitivity of brain cholinesterase to cypermethrin toxicity in freshwater teleost Tilapia mossambica

Cypermethrin at sublethal concentrations induced significant changes in acetylcholinesterase (AChE) activity and acetylcholine (ACh) content in the brain tissue of both juvenile and adult-fish. Maximum inhibition of AChE activity is noticed at 6h and 12h after exposure to cypermethrin in juvenile and adult fish respectively. In contrast, the ACh levels registered an elevation in both the cases. During subsequent periods the rate of recovery in AChE activity and ACh content is variable in both the groups.