EEG of rhesus monkeys following prolonged low-level feeding of pesticides

Bioelectrical activity of brain in Rana tigrina (Daudin) in response to phosalone poisoning

An acute dose of phosalone, intraperitoneally injected to Rana tigrina alters the bioelectrical activity of the brain. The frequency levels of delta, theta, alpha, and beta waves remained similar in both control and experimental groups, while the amplitude of the waves was significantly decreased by 40 to 60% in the latter group. The total work done (TWD) was also significantly reduced. The above disturbance in the brain electrical activity may have correlation to the inhibition of cation-linked ATPase, as well as the cholinesterase activity.

Effects of single and repeated administration of endosulfan on behaviour and its interaction with centrally acting drugs in experimental animals: a mini review

The organochlorine cyclodiene insecticide, endosulfan readily penetrates into the brain. The neurotoxic action of endosulfan has been attributed to its α-isomer. Endosulfan sulphate which is a chief metabolite of endosulfan seems to contribute to its acute neurotoxic action which is manifested by clonic convulsions in experimental animals. Convulsant and proconvulsant effects of endosulfan are apparent after its chronic exposure at low dose levels. These effects have been attributed to its γ-aminobutyric acid antagonistic action. Repeated exposure to low doses has resulted in behavioral changes too. Endosulfan-induced hyper-excitability has been associated with its muscarinic receptor stimulating action. The insecticide has been shown to produce aggressive behaviour and learning impairment by activating serotonergic mechanism. A dopaminergic involvement has been suggested for endosulfan-induced hypermotoractivity and circling movement. Animals exposed chronically to low doses of the insecticide have responded more markedly than control animals to the pharmacological actions of diazepam, chlorpromazine, pentobarbital and ethanol. The findings reviewed here emphasize awareness that chronic occupational exposure to low doses of endosulfan may result not only in behavioral abberations but in hazardous interaction with centrally acting drugs too.

The influence of carbaryl on the uptake of (3H)-noradrenaline (3H)-NA by rat hypothalamic slices

The uptake of (3H)-NA by rat hypothalamic slices was investigated following carbaryl poisoning. The insecticide was administered to rats orally in a single dose of 50% LD50 and of 20% LD50, and in repeated dosing for 14 days (5% LD50 daily). The kinetics of (3H)-NA uptake was defined by the modified Lineweaver-Burk plots (Rmax was used instead of Vmax and Km was replaced with t05 max). The results indicated that in all the experiments carbaryl elevated the (3H)-NA uptake by hypothalamic slices in a dosage dependent fashion (insignificantly at the 20% LD50 dose level, p greater than 0.05) as evidenced by the increased Rmax values. However, carbaryl simultaneously decreased the kinetics of the process in the hypothalamus since t0.5max values were enhanced (insignificantly at the 5% LD50 dose level, p greater than 0.05). Carbaryl produced a dose-dependent increase of t0.5max values. The changes in the (3H)-NA uptake may be related to the increase of NA level in the hypothalamus following exposure to carbaryl observed by other authors.

Effects of cyclodiene compounds on calcium pump activity in rat brain and heart

The in vitro and in vivo effects of aldrin, dieldrin, and endrin on calmodulin regulated Ca2+-pump activity in rat brain synaptosomes and heart sarcoplasmic reticulum were investigated. All the 3 cyclodiene compounds inhibited both brain synaptosomal and heart sarcoplasmic reticulum Ca2+-pump activity in vitro in a concentration dependent manner. Calmodulin depleted Ca2+-pump activity was insensitive to the action of toxic compounds. Oral administration of pesticides (0.5-10 mg/kg) to rats similarly decreased the Ca2+-pump activity, in addition to decreasing the levels of calmodulin of both brain and heart thus indicating disruption in membrane Ca2+ transport mechanisms. Exogenous addition of calmodulin (1-20 micrograms) could effectively reverse the pesticide induced inhibition. Ca2+-pump activity is more sensitive to the 3 cyclodiene compounds in brain than in heart. The results of the present study indicate that the cyclodiene compounds may produce neurotoxic effects by altering calmodulin regulated calcium dependent events in neurons.

Distribution of neurotoxic esterase activity in the brain of control and diisopropyl phosphorofluoridate-treated hens: in vivo and in vitro exposure

Neurotoxic esterase (NTE) is a protein which is hypothesized to be the site where certain organophosphorus compounds act to produce delayed-onset neurotoxicity. Adult white Leghorn hens (Gallus domesticus) were injected subcutaneously (0.5 mg/kg and 2.0 mg/kg) with diisopropyl phosphorofluoridate (DFP). Control and DFP-treated hens were killed 24 h after treatment and their brains sectioned into telencephalic, cerebellar, diencephalic, mesencephalic, metencephalic tegmentum, and myelencephalic portions. NTE activity was highest in the telencephalon and cerebellum, and brainstem activity progressively decreased moving caudally with the myelencephalon approaching reported spinal cord levels. Percent inhibition of NTE by DFP (0.5 mg/kg and 2.0 mg/kg) did not differ among brain regions or whole brain. The IC50's for DFP were not significantly different either among brain regions or whole brain. The results suggest that nervous system regions with higher NTE levels are protected from delayed neuropathy by virtue of overabundant NTE activity.

Effects of oral and intramuscular carbaryl administrations on repeated chain acquisition in monkeys

A type of learning task was utilized to determine the effective dose of carbaryl on Macaca fascicularis for both oral and in routes of administration. Monkeys were required to press four buttons in a set order; the order was changed daily. A baseline reversal design was utilized to test all animals several times at each concentration. The im carbaryl injections resulted in consistent, statistically reliable decrements in total session time and increases in errors at 5 and 10 mg/kg for the 4 animals in this section of the experiment, but produced no change in performance at 1 mg/kg. Errors increased in 3 of 4 monkeys after 3 mg/kg injections. Oral doses as high as 50 mg/kg were not consistently effective in changing performance on the task in any of 5 animals included in this section of the experiment. Some support was given to the suggestion that monkeys are more tolerant of carbaryl than are rats. These are the first reported effects (other than the LD50) of carbaryl in monkeys.

Deldrin toxicity and successive discrimation reversal in squirrel monkeys (Saimiri sciureus)

Seven squirrel monkeys were systematically exposed to dieldrin (C12H10DC16) at two oral doses: 0.10 and 0.01 mg/kg-day. Two zero-dose controls were included. After 55 days of exposure dose assignments were shifted and continued for an additional 54 days. The higher dose group was shifted to zero exposure and lower dose group was shifted to high-dose exposure. Controls continued at zero exposure. The monkeys were presented with a visual nonspatial successive discrimination reversal task. During the first 55 days (preshift), control and low-dose monkeys learned the task; high-dose monkeys did not (p less than 0.001). During the subsequent 54 days (postshift), all groups performances remained at the approximate level achieved at the end of the preshift period. It was concluded that the high dose disrupted learning acquisition. This effect is speculated to be attributed to disruption of hippocampal activity. The low dose had no effect on task acquisition or maintenance.