Sublethal effects of resin glycosides from the periderm of sweetpotato storage roots on Plutella xylostella (Lepidoptera: Plutellidae).

Resin glycoside material extracted from the periderm tissue of storage roots from sweetpotato, Ipomoea batatas (L.) Lam., was bioassayed for effects on survival, development, and fecundity of the diamondback moth, Plutella xylostella (L.). The resin glycoside was incorporated into an artificial diet and fed to P. xylostella larvae. First instars were placed individually into snap-top centrifuge vials containing artificial diet with one of six concentrations of resin glycoside material (0.00, 0.25, 0.50, 1.00, 1.50, and 2.00 mg/ml). Each replication consisted of 10 individuals per concentration, and the experiment was repeated 13 times. Vials were incubated at 25 degrees C and a photoperiod of 14:10 (L:D) h in a growth chamber. After 6 d, surviving larvae were weighted and their sex determined, then returned to their vials. Later, surviving pupae were weighed and incubated at 25 degrees C until moths emerged. Females were fed, mated with males from the laboratory colony, and allowed to lay eggs on aluminum foil strips. Lifetime fecundity (eggs/female) was measured. There were highly significant negative correlations between resin glycoside levels and survival, and between glycoside levels and larval weight after 6 d of feeding. For larvae that lived at least 6 d, there was no additional mortality that could be attributed to the resin glycoside material. However, there was a significant positive correlation between glycoside dosages and developmental time of larvae (measured as days until pupation). Lifetime fecundity also was negatively affected at sublethal doses. Resin glycosides may contribute to the resistance in sweetpotato breeding lines to soil insect pests.

Prepulse inhibition of acoustic startle, a measure of sensorimotor gating: effects of antipsychotics and other agents in rats.

Schizophrenic patients are deficient in various neurologic measures reflecting information processing. One such measure in prepulse inhibition (PPI) of acoustic startle, in which schizophrenics display less inhibition than normal subjects. PPI is also diminished in rats treated with psychotomimetic drugs such as amphetamine and phencyclidine. PPI has been suggested as a model relevant for studying the pathophysiology of schizophrenia. We studied the effect of a variety of antipsychotics and putative antipsychotics and some key reference compounds on the acoustic startle response (ASR) and PPI. Some, but not all, antipsychotics tested (mainly selective dopamine D2 antagonists) enhanced PPI. Remoxipride and clozapine, both of which are antipsychotics, and the very potent and highly selective D2 antagonist, NCQ-298, did not. It is concluded that enhanced PPI in otherwise untreated rats does not reflect antipsychotic efficacy. We further noted that the effect on PPI was independent of the effect on ASR.

Current usage of contrast agents, anticoagulant and antiplatelet drugs in angiography and angioplasty in the UK.

Currently, there is no consensus in the UK on what constitutes best angiographic practice. To provide a basis for discussion a questionnaire was sent to all Radiology and Cardiology departments in the UK. Information was requested on practice during diagnostic angiography and angioplasty regarding the type of contrast agent used, whether and how flush solution or contrast agents themselves were heparinised, and whether bolus doses of heparin were administered. The use of other supplementary drugs including corticosteroids was also explored. Two hundred of 353 (57%) of questionnaires were returned. Over 80% who replied used non-ionic contrast agents for all angiographic procedures. The majority of the smaller group, using ionic contrast agents for uncomplicated procedures, resorted to non-ionic contrast agents in a range of circumstances in both diagnostic angiography and angioplasty. Heparinized flush solutions were used by over 75% for both types of angiographic procedures, but employing a wide range of doses. Bolus doses of heparin were administered by over 80% performing angioplasty, again in a wide range of doses, with only (a few) cardiologists monitoring the anticoagulant effect by measuring the activated whole blood clotting time in the angiographic suite. Over 70% used aspirin or dipyridamole as supplementary agents, at the time of the angioplasty and, subsequently, continued these medications for a variable period. Corticosteroid prophylaxis for high risk patients, very variably defined, was felt necessary by 58%. A wide range of regimes of both dose and timing was noted.

The atypical antipsychotic, remoxipride, blocks phencyclidine-induced disruption of prepulse inhibition in the rat.

The effect of various typical (haloperidol) and atypical (clozapine, raclopride, remoxipride) antipsychotics on phencyclidine (PCP)-induced disruption of sensorimotor gating was tested in rats using an acoustic startle paradigm. Clozapine (4-40 mumol/kg), haloperidol (1-5 mumol/kg) and raclopride (1-12 mumol/kg) failed to reverse PCP-induced disruption of prepulse inhibition (PPI) of the acoustic startle response. In contrast, remoxipride (12-60 mumol/kg) caused a dose-dependent block of this effect. PCP-induced disruption of PPI is a widely accepted animal model of a corresponding behavioural deficit observed in schizophrenia although little evidence has been presented that it is in fact sensitive to antipsychotic agents. The present results indicate that remoxipride behaves in a unique way in this model compared to clozapine, haloperidol and raclopride.

Preclinical findings with new antipsychotic agents: what makes them atypical?

Many early antipsychotics such as haloperidol, while effective in treating the symptoms of schizophrenia, cause detrimental side effects and moreover induce nonspecific sedation in many patients. Newer drugs such as remoxipride are as effective as the classical antipsychotics but induce fewer debilitating side effects. These clinical properties are reflected to some extent in their preclinical pharmacology, with drugs such as remoxipride having effects on various preclinical behavioural and biochemical models that are quite different to those exerted by drugs such as haloperidol. This article reports some new behavioural data and discusses the various mechanisms that can underlie the effect of new atypical antipsychotics.

The quasi-morphine withdrawal syndrome: effect of cannabinol, cannabidiol and tetrahydrocannabinol.

Delta-9-tetrahydrocannabinol (THC), the main psychoactive principle of cannabis, has been shown to attenuate the exhibition of signs of the quasi-morphine withdrawal syndrome in rats. Cannabinol (CBN) showed the same activity but required a dosage of approximately eight times that of THC to produce an equivalent effect. Cannabidiol was without effect at the dosage levels used. The efficacy of these cannabinoids and the potency differences recorded in this study are in accord with their effects on other behaviours, both in experimental animals and in man. The activity of THC and CBN was not affected by the narcotic antagonist, naloxone.

Self-stimulation of the nucleus accumbens and some comparisons with hypothalamic self-stimulation.

Rats were trained to respond for electrical stimulation of the nucleus accumbens (ACB) or lateral hypothalamus (HYP) in a shuttle-box apparatus. Whereas the HYP rats showed rapid acquisition and stabilization of performance, the ACB rats were slow to learn the task and commonly took longer than 20 daily sessions to stabilize. Once stabilized, both groups responded with similarly vigorous performance. All rats displayed a predominantly locomotor behaviour, which was almost totally devoid of exploratory behaviours typically associated with self-stimulation. The absence of stimulus-bound behaviours was particularly notable in the ACB group. These rats, but not the HYP rats, showed an increase in the latency to initiate stimulation during the daily 25-min test sessions. Depriving the animals of a single self-stimulation session caused a decrease in the latency of ACB rats to initiate on the following day while having no effect on the HYP rats. All ACB rats gradually developed convulsive seizures during the first 3 weeks of testing which subsequently became more frequent and severe. None of the HYP rats showed any involuntary motor effects. The results show that ACB self-stimulation is a very different phenomenon to HYP self-stimulation, and suggest that, in addition to reward and aversion, ACB self-stimulation may involve a stereotyped ritual controlled partly by adaptation and conditioning.