Induction of behavioral supersensitivity to apomorphine by DFP treatment

The effect of DFP, a long-acting inhibitor of acetylcholinsterase, on apomorphine-induced climbing behavior, was tested in mice. Twelve hours following the intraperitoneal administration of a single dose of DFP, animals demonstrated a significant increase in apomorphine-induced climbing behavior. This effect was not observed twenty-four hours following DFP pretreatment. These results suggest that acute administration of a cholinomimetic agent, may produce behavioral supersensitivity to dopamine agonists.     

D-LSD binding to brain homogenates: possible relationship to serotonin receptors

Using a rapid filtration technique we find stereospecific high-affinity $\text{d}$-LSD binding (4 × 10^?9M, half-saturation) in brain fractions from a number of subcortical as well as cortical brain regions. Among the putative neurotransmitters tested only serotonin effectively displaces $\text{d}$-LSD from this specific binding site. Moreover, only the serotonin-displaceable component of binding is saturable in a high-affinity range. No change is observed in specific $\text{d}$-LSD binding in forebrain homogenates from rats in which ascending serotonergic pathways are destroyed by lesions in the raphe nucleus. We conclude that a vast majority of the $\text{d}$-LSD binding sites may be associated with a postsynaptic serotonin receptor rather than a presynaptic receptor associated with serotonergic (raphe) inputs.     

Progressive behavioral changes during chronic lidocaine administration: relationship to kindling.

Chronic, five times weekly administration of lidocaine (60 mg/kg, i.p.) to rats resulted in the progressive development of abnormal eating behavior and seizures. Experimental rats became omniphagic, eating significantly more feces, straw, and gauze than controls. Following an average of 15 lidocaine injections unassociated with seizures, animals began to have major motor convulsions, which then increased in frequency and duration. A pharmacological kindling mechanism is suggested for the progressive effects of lidocaine on behavior and seizures.     

Parity-associated reductions in behavioral sensitivity to opiates

Behavioral and physiological responses differ between primiparous and multiparous female rodents. Specifically, multiparous females respond with the full repertoire of maternal behaviors much more rapidly and with greater intensity than their primiparous counterparts. Since opiates inhibit the expression of maternal behavior in postpartum rats and can be reversed by means of the opiate antagonist naloxone, we investigated whether multiparous females would be resistant to the inhibitory effects of opiates on maternal behavior, relative to primiparous females. In Experiment 1 we evaluated the effects of a range of doses of morphine sulfate (MS; 0.625, 1.25, 2.5, 5.0, and 10.0 mg/kg or saline) on maternal behavior in primiparous females on Days 5-6 of lactation. The 5.0 and 10.0 mg/kg doses effectively disrupted maternal behavior, whereas the lower doses were ineffective or only marginally disruptive. In Experiment 2, age-matched female rats were timed-mated and tested for maternal behavior from Day 5 to 13 of lactation, after daily injections of the 5.0 mg/kg dose of MS. On Day 5 of lactation, this morphine treatment eliminated full maternal behavior in 87% of the primiparous animals, but only 37% of the multiparous animals were affected. By Day 10 of lactation, 100% of the multiparous females displayed full maternal behavior after MS treatment, whereas only 69% of primiparous females were responsive. In Experiment 3, analgesic responses were measured both in rats experiencing their initial or second pregnancy, and in postpartum, lactating rats after MS (5.0 mg/kg) administration. Using a tail-flick apparatus to measure analgesia, we found multigravid females to be significantly less analgesic prepartum than primigravid females, suggesting less sensitivity to endogenous opioids.(ABSTRACT TRUNCATED AT 250 WORDS)     

Transformations in flagellar structure of Rhodobacter sphaeroides and possible relationship to changes in swimming speed

Rhodobacter sphaeroides is a photosynthetic bacterium which swims by rotating a single flagellum in one direction, periodically stopping, and reorienting during these stops. Free-swimming R. sphaeroides was examined by both differential interference contrast (DIC) microscopy, which allows the flagella of swimming cells to be seen in vivo, and tracking microscopy, which tracks swimming patterns in three dimensions. DIC microscopy showed that when rotation stopped, the helical flagellum relaxed into a high-amplitude, short-wavelength coiled form, confirming previous observations. However, DIC microscopy also revealed that the coiled filament could rotate slowly, reorienting the cell before a transition back to the functional helix. The time taken to reform a functional helix depended on the rate of rotation of the helix and the length of the filament. In addition to these coiled and helical forms, a third conformation was observed: a rapidly rotating, apparently straight form. This form took shape from the cell body out and was seen to form directly from flagella that were initially in either the coiled or the helical conformation. This form was always significantly longer than the coiled or helical form from which it was derived. The resolution of DIC microscopy made it impossible to identify whether this form was genuinely in a straight conformation or was a low-amplitude, long-wavelength helix. Examination of the three-dimensional swimming pattern showed that R. sphaeroides changed speed while swimming, sometimes doubling the swimming speed between stops. The rate of acceleration out of stops was also variable. The transformations in waveform are assumed to be torsionally driven and may be related to the changes in speed measured in free-swimming cells. The roles of and mechanisms that may be involved in the transformations of filament conformations and changes in swimming speed are discussed.     

Nicotine-induced changes in the metabolism of specific brain proteins

The effect of acute and chronic nicotine on the metabolism of specific brain proteins was examined by measuring incorporation of labeled valine into protein, with densitometric scanning of proteins resolved by gel electrophoresis. Acute and chronic administration of nicotine (0.4 mg/kg per 30 min for 2 hours, s.c., or 0.5 mg/kg per 30 min for 5 days (Alzet mini-pump implanted subcutaneously) reduced incorporation of [¹⁴C]valine administered by approximately 6–7%. The results with chronic nicotine administration indicated a lack of tolerance for this effect of nicotine. Mecamylamine, a nicotinic ganglionic antagonist, does not seem to block the inhibition of protein synthesis. Small increases in protein content were observed in a high- and a low-molecular-weight region of SDS-polyacrylamide gel, used to separate proteins from newborn brain. In adult brain after chronic nicotine administration, selective increases and a decrease were seen in selective bands. Results are consonant with selective effects of nicotine on the synthesis or degradation of specific brain proteins.Special Issue Dedicated to Dr. Abel Lajtha.     

Studies of myelin proteins in multiple sclerosis brain tissue

Using radioimmunoassays (RIA) for the myelin specific proteins, myelin proteolipid protein (PLP) and myelin basic protein (MBP) and an enzyme assay for the activity of the myelin marker enzyme 23 cyclic-3 phosphohydrolase (CNPase), we have studied plaque, periplaque and normal appearing white matter (NAWM) regions of multiple sclerosis (MS) brain tissue, as well as normal control brain tissue. We found that all three myelin proteins are decreased in all regions, including NAWM, of MS brain, with a decreasing gradient from NAWM to periplaque to plaque. The NAWM was not significantly different from the periplaque region. Surprisingly, when the ratios of the proteins were calculated, MBP activity, although decreased was found to be relatively preserved.     

Age-dependent changes in sensitivity to antigen: its relationship with the antigen processing system.

The relationship between the antigen processing or accessory cell system and the maturation, with age, of antibody-producing capability was investigated in the mouse. This was done by analyzing the antibody responses given by immunocompetent cells from neonatal and from adult male mice in an identical antigen-processing system environment. Specifically, 4 x 10(7) normal spleen cells from either 12-day-old or adult mice were challenged with varying numbers of SRC in adult irradiated syngeneic recipients. The subsequent IgM and IgG2a PFC responses for both age groups were analyzed in terms of antigen dose-antibody response curves. Analyses of these curves indicate: 1) the dose of antigen required to elicit the optimal antibody response is essentially identical for both age groups and (2) the bandwidths obtained using neonatal donors are significantly narrower than those obtained with adult donors. Whereas, intact neonatal and adult mice exhibit differences in antigen optimal doses, these differences are eliminated when the immunocompetent cells are stimulated in the presence of identical antigen-processing systems. It is concluded that maturation of the antigen-processing system results in an increased sensitivity to antigen. Examination of the bandwidths of the dose-response curves revealed that immunocompetent cells from the young mice, either in situ or in adult irradiated recipients exhibited narrower bandwidths than did their adult counter parts. Thus, the increase in bandwidth observed with age is attributed to changes in the population of immunocompetent cells--perhaps a reflection of increased diversity, and is not due to the antigen-processing system. Quantitation of the antigen-processing function using accessory cell-depleted and partially restored mice indicated that when IgG responses were compared a higher frequency of accessory cells was demonstrated in adultspleens as opposed to neonatal spleens.     

Erythrocyte membrane fluidity and changes in plasma lipid composition: a possible relationship in childhood obesity

We have studied plasma lipid patterns and erythrocyte membrane fluidity in 60 obese children and 20 normal children. Plasma levels of total cholesterol and associated low-density lipoproteins were significantly increased in 20 obese patients with respect to controls. A significant decrease in membrane fluidity, measured as an increase in the fluorescence polarization value of the probe 1,6-diphenyl-1,3,5-hexatriene, associated with an increase in the cholesterol/protein ratio has been shown in obese patients. The study of the correlation between erythrocyte membrane fluidity and plasma cholesterol has indicated that significant changes in fluidity and membrane lipid composition also occur in erythrocytes of obese patients with normal plasma lipid levels. These findings confirm that the erythrocyte membrane responds very early to modifications of plasma lipoproteins and suggest that in childhood obesity a modified transfer of cholesterol from plasma to erythrocyte membrane may take place.     

Nicotinic autoreceptor function in rat brain during maturation and aging: possible differential sensitivity to organophosphorus anticholinesterases

Acetylcholine (ACh) release is modulated pre-synaptically by both muscarinic and nicotinic receptor-mediated processes. While muscarinic autoreceptors inhibit ACh release, nicotinic autoreceptors enhance ACh release and thus disruption of these processes could potentially affect cholinergic toxicity following exposure to anticholinesterases. Marked age-related differences in sensitivity to some organophosphorus (OP) anticholinesterases have been reported. We compared nicotinic autoreceptor function (NAF) during maturation and aging and evaluated its potential modulation by the common OP insecticide, chlorpyrifos (CPF). Cortical synaptosomes were pre-loaded with [3H]choline, superfused (0.6 ml/min) with physiological buffer and [3H]ACh release was evoked with potassium (KCl, 9 mM), with or without co-addition of exogenous ACh to stimulate nicotinic autoreceptors. Fractions of perfusate were subsequently collected and area under the curve (AUC) for [3H] was analyzed by scintillation counting. The difference in evoked release due to co-addition of exogenous ACh was defined as NAF. Under these conditions, atropine (ATR, 0.1 microM) appeared requisite for NAF; thus this muscarinic antagonist was subsequently added to all perfusion buffers. In synaptosomes from adult tissues, exogenous ACh (3-100 microM) significantly increased release in a concentration-dependent manner. The nicotinic antagonist mecamylamine (MEC, 100 microM) substantially reduced the potassium-evoked release elicited by co-addition of ACh (10 microM). Interestingly, the nicotinic agonists nicotine (NIC) and dimethylphenylpiperazinium (DMPP; 0.1-10 microM) had no effect on release. The active metabolite of CPF (i.e. chlorpyrifos oxon (CPO), 1-10 microM) inhibited NAF in vitro. Maturation-related expression of NAF was noted (AUC with co-addition of 10 microM ACh: 7-day rats, 7+/-6; 21-day rats, 44+/-6; 90-day rats, 196+/-37; 24-month rats, 173+/-52). NAF was substantially reduced (67-91%) 96 h after maximum tolerated dosages of CPF in adult and aged rats (279 mg/kg, sc) but not in juveniles (127 mg/kg, sc), even though AChE inhibition was similar among the age groups (>80%). Together these data suggest that NAF is differentially expressed during maturation and that this neuromodulatory process may be selectively altered by some OP insecticides, potentially contributing to age-related differences in response to AChE inhibitors. As NAF has been postulated to be activated under conditions of 'impaired' cholinergic function, selective alteration of this pre-synaptic process by OP anticholinesterases may be also important in age-related conditions associated with cholinergic hypofunction.     

Crustacean social behavioral changes in response to isolation

Periods of isolation during which animals have no social contact are common in the design of behavioral experiments. They are used, for example, to test memory and recognition responses, or to ensure a baseline condition before experimental manipulations commence. We investigated the effect of isolation periods on the aggressive behavior of matched pairs of the crayfish Cherax destructor in two contexts. The first experiment tested the effects of a period of isolation between two encounters. The second experiment tested the effects of isolation before an encounter by pairing one crayfish from a communal living environment with another crayfish from an isolated one. Fight outcome and aggression levels were analyzed, resulting in three conclusions about the social biology of C. destructor. First, encounters between familiar opponents are influenced by the outcome of the familiarization fight for about 2 weeks. Second, the level of aggression and the outcome of an encounter are affected over different time frames. Third, individuals that are isolated before an encounter can be disadvantaged. These data suggest that isolation, or events that occur during periods of isolation, affect multiple elements of social behavior in C. destructor. This suggestion has implications for the interpretation of previous results and future studies in crustaceans and other taxa.     

Studies on the turnover of mouse brain synaptosomal proteins

(l) The half-lives of the proteins of various fractions of whole mouse brain increase with increasing insolubility; the supernatant and hypotonic-extractable proteins had half-lives of about 13 days, whereas the membrane proteins solubilized with Triton X-100 and SLS had half-lives of about 18 days. The proteins of the subfractions of synaptosomes had half-lives ranging from 15 to 19 days; those in the cytoplasm had a half-life of 18·3 days, in the membranes, about 17 days and in the synaptic vesicles, 15·6 days. (2) Although the half-life of the synaptic vesicles was not significantly different from that of other synaptosomal subfractions, the vesicles exhibited a different protein pattern on acrylamide gels, an observation which implies that the proteins of the vesicles are qualitatively different from those of other synaptic membranes. (3) The uptake of labelled lysine into the cytoplasm of the synaptosomes of youg mice in vivo was very rapid. (4) The data derived from the relative specific radioactivities of synaptosomal fractions compared with their whole brain analogs support the contention that a sizeable fraction of the synaptosomal cytoplasmic protein was transported to the synapse by axoplasmic flow. The relative specific radioactivities of synaptosomal membrane and synaptic vesicle proteins rose much more quickly than the comparable activities for the cytoplasmic material, and the alternate possibility of synthesis in situ is discussed.