Effects of diazepam on the behaviour of weaned pigs in three putative models of anxiety

The present study examined the effects of diazepam (a widely used anxiolytic benzodiazepine) on the behavioural response of pigs to three novel experimental situations used to measure anxiety-related behaviour in rodents. Twelve weaned pigs (two pairs from each of the three litters) were tested in an elevated plus-maze at the age of 6 weeks, a light/dark test at the age of 7 weeks and an open-field test at the age of 8 weeks. Six of the pigs were pre-treated with diazepam (valium) and the other six with saline (control). In the elevated plus-maze, diazepam-treated pigs had a higher number of entries into open arms (P=0.04), spent more time on open arms (P=0.07), and had a higher number of total arm entries (P=0.05) than pigs from the control group. However, diazepam had no significant effects on behaviour in the light/dark test (i.e., latency to enter lit compartment, number of entries into lit compartment and the time spent in lit compartment) or the open-field test (i.e., number of lines crossed, number of entries into centre). In summary, the anxiolytic effects of diazepam on the pigs' behaviour were only demonstrated in the elevated plus-maze, where the time spent on open arms and the number of entries into open arms could be interpreted as measures of anxiety in pigs.     

Lavender Oil-Potent Anxiolytic Properties via Modulating Voltage Dependent Calcium Channels

Recent clinical data support the clinical use of oral lavender oil in patients suffering from subsyndromal anxiety. We identified the molecular mechanism of action that will alter the perception of lavender oil as a nonspecific ingredient of aromatherapy to a potent anxiolytic inhibiting voltage dependent calcium channels (VOCCs) as highly selective drug target. In contrast to previous publications where exorbitant high concentrations were used, the effects of lavender oil in behavioral, biochemical, and electrophysiological experiments were investigated in physiological concentrations in the nanomolar range, which correlate to a single dosage of 80 mg/d in humans that was used in clinical trials. We show for the first time that lavender oil bears some similarities with the established anxiolytic pregabalin. Lavender oil inhibits VOCCs in synaptosomes, primary hippocampal neurons and stably overexpressing cell lines in the same range such as pregabalin. Interestingly, Silexan does not primarily bind to P/Q type calcium channels such as pregabalin and does not interact with the binding site of pregabalin, the α2δ subunit of VOCCs. Lavender oil reduces non-selectively the calcium influx through several different types of VOCCs such as the N-type, P/Q-type and T-type VOCCs. In the hippocampus, one brain region important for anxiety disorders, we show that inhibition by lavender oil is mainly mediated via N-type and P/Q-type VOCCs. Taken together, we provide a pharmacological and molecular rationale for the clinical use of the oral application of lavender oil in patients suffering from anxiety.     

Loop diuretics have anxiolytic effects in rat models of conditioned anxiety

A number of antiepileptic medications that modulate GABA(A) mediated synaptic transmission are anxiolytic. The loop diuretics furosemide (Lasix) and bumetanide (Bumex) are thought to have antiepileptic properties. These drugs also modulate GABA(A) mediated signalling through their antagonism of cation-chloride cotransporters. Given that loop diuretics may act as antiepileptic drugs that modulate GABAergic signalling, we sought to investigate whether they also mediate anxiolytic effects. Here we report the first investigation of the anxiolytic effects of these drugs in rat models of anxiety. Furosemide and bumetanide were tested in adult rats for their anxiolytic effects using four standard anxiety models: 1) contextual fear conditioning; 2) fear-potentiated startle; 3) elevated plus maze, and 4) open-field test. Furosemide and bumetanide significantly reduced conditioned anxiety in the contextual fear-conditioning and fear-potentiated startle models. At the tested doses, neither compound had significant anxiolytic effects on unconditioned anxiety in the elevated plus maze and open-field test models. These observations suggest that loop diuretics elicit significant anxiolytic effects in rat models of conditioned anxiety. Since loop diuretics are antagonists of the NKCC1 and KCC2 cotransporters, these results implicate the cation-chloride cotransport system as possible molecular mechanism involved in anxiety, and as novel pharmacological target for the development of anxiolytics. In view of these findings, and since furosemide and bumetanide are safe and well tolerated drugs, the clinical potential of loop diuretics for treating some types of anxiety disorders deserves further investigation.     

Piplartine, an amide alkaloid from Piper tuberculatum, presents anxiolytic and antidepressant effects in mice

In the present work, we studied the effects of piplartine (PIP), an amide alkaloid isolated from the roots of Piper tuberculatum (Piperaceae), in the elevated plus maze, open field, rota rod, pentylenetetrazole (PTZ)-induced seizures, and forced swimming tests, in mice (Swiss, male, 25 g) to assess anxiolytic, sedative, muscle relaxant, anticonvulsant and antidepressant effects, respectively. Results showed that PIP (50 and 100 mg/kg, i.p.), similarly to diazepam, significantly increased not only the number of entrances (100% and 66%, respectively) but also the time of permanence in the open arms (104% and 199%, respectively), indicating that PIP presents an anxiolytic activity. Both effects were completely blocked by the previous administration of flumazenil what suggests the involvement of benzodiazepine type receptors. In the open field test, although PIP did not alter the number of crossings, it significantly increased grooming (103% and 119%) and rearing (60% and 23%), at the doses of 50 and 100 mg/kg respectively, as compared to controls. However, in the rota rod test, PIP was devoid of effect. Although in the PTZ-induced convulsion test, PIP did not alter the latency time for the onset of the first convulsion, as compared to controls, it significantly reduced in 58% and 60%, respectively, the animal's latency time to death. Furthermore, a significant and dose-dependent decrease in the immobility time, as evaluated by the forced swimming test, was observed after PIP administration (41% and 75% decrease, at the doses of 50 and 100 mg/kg, respectively), suggesting an antidepressant effect, similarly to that observed with imipramine, a classical antidepressant drug used as standard. In conclusion, we showed that PIP presents significant anxiolytic and antidepressant activities, making this drug potentially useful in anxiety and depression.     

Effects of the LHRH antagonist Cetrorelix on affective and cognitive functions in rats

The decapeptide LHRH antagonist, Cetrorelix, inhibits gonadotropin and sex-steroid secretion. Cetrorelix is used for IVF-ET procedures and for the treatment of benign prostatic hyperplasia, endometriosis and leiomyomas. However little is known about the effects of Cetrorelix on brain functions. Previously we have tested Cetrorelix in mice on the impairment of the consolidation of a passive avoidance behavior caused by beta-amyloid 25–35, anxiolytic action in the plus-maze, antidepressive action in a forced swimming test, tail suspension and open-field behavior following its administration into the lateral brain ventricle. In the present study we repeated and extended the experiments in rats in order to determine whether there are species differences in the action of Cetrorelix between mice and rats. The effects of Cetrorelix evaluated included the methods used in mice without tail suspension test and extended by measuring core temperature. Cetrorelix fully blocked the impairment of the consolidation of passive avoidance learning when given icv 30 min following administration of beta-amyloid 25–35. If beta-amyloid 25–35 and Cetrorelix were given simultaneously, Cetrorelix was ineffective. Cetrorelix elicited slight anxiogenic and stronger anxiolytic action in the plus-maze, depending on the dose used. In the forced swimming tests, Cetrorelix showed antidepressive-like action. In open-field behavior tests Cetrorelix displayed a U-type action on locomotion with 0.5 and 2 µg increasing locomotion, and increase rearing but and had no effect on grooming at 0.5–2 µg. Cetrorelix had no action on core temperature. Our findings demonstrate that Cetrorelix is able to correct the impairment of the memory consolidation caused by beta-amyloid 25–35. Cetrorelix elicits anxiolytic and antidepressive action, slightly increases locomotion and rearing in open field, but it does not influence the core temperature. The results obtained in rats are similar to those reported previously by us in mice. Collectively our findings confirm the effects of Cetrorelix on brain function in two species and suggest the possible merit of a clinical trial with Cetrorelix in patients with anxiety, depression and Alzheimer's disease.     

The contribution of latent inhibition to reduced generalization after pre-exposure to the test stimulus

Two experiments assessed the contribution of latent inhibition to the generalization-reducing effects of pre-exposure to the test stimulus using a taste aversion procedure in rats. In both experiments, lithium chloride induced illness was paired with a flavor compound (AX) of either salt or sugar (A or B) and hydrochloric acid (X). Generalization of the resulting aversion to a test compound (BX), was assessed after varying pre-exposure to BX, X, and B. Experiment 1 showed that generalization to BX was less when BX itself had been exposed than equivalent pre-exposure to either B and X separately or to B and a new compound (CX). Experiment 2 showed that levels of generalization varied directly as a function of the amount of pre-exposure to BX. The findings show that latent inhibition alone cannot account for the generalization-reducing effect of pre-exposure to BX.     

An ethological analysis of open-field behaviour in chickens

Two salient but previously unacknowledged aspects of open-field testing involve contact with a potential predator, as a consequence of placement in the open field by a human, and separation from imprinted companions. As a result we propose that open-field behaviour in chickens (Gallus gallus) represents a compromise between opposing tendencies to reinstate contact with conspecifics and minimize detection in the face of possible predation. Five experiments were conducted to test various implications of this model. Manipulations designed to enhance the predatory overtones of open-field testing were found to postpone reinstatement behaviours (e.g. distress calling and escape attempts) and prolong behaviours that serve to minimize detection (e.g freezing). Unlike the more traditional view of open-field behaviour as an index of general emotionality, our model suggests that the principal reason for movement is based on attempts to reinstate social contact. In support of the model, birds tested in the presence of cagemates showed significantly longer durations of freezing than those tested individually. The same was true for birds maintained in social isolation for two days prior to testing. The applicability of this approach to conceptualizing the behaviour of chickens in the open field is discussed, and the supposed relationship between fear and distress calling is critically evaluated.     

Phytochemical and biological analysis of Skullcap (Scutellaria lateriflora L.): A medicinal plant with anxiolytic properties

The phytochemistry and biological activity of Scutellaria lateriflora L. (American skullcap) which has been traditionally used as a sedative and to treat various nervous disorders such as anxiety was studied. In vivo animal behaviour trials were performed to test anxiolytic effects in rats orally administered S. laterifolia extracts. Significant increases in the number of entries into the center of an "open-field arena"; number of unprotected head dips, number of entries and the length of time spent on the open arms of the Elevated Plus-Maze were found. The identification and quantification of the flavonoid, baicalin in a 50% EtOH extract (40 mg/g) and its aglycone baicalein in a 95% EtOH extract (33 mg/g), as well as the amino acids GABA in H2O and EtOH extracts (approximately 1.6 mg/g) and glutamine in a H2O extract (31 mg/g), was performed using HPLC. These compounds may play a role in anxiolytic activity since baicalin and baicalein are known to bind to the benzodiazepine site of the GABAA receptor and since GABA is the main inhibitory neurotransmitter.     

Behavioral effects of acute and chronic triazolam treatments in albino rats

Previous behavioral studies on triazolam (TZ), which are small in number, could only speculate about tolerance to the anxiolytic effect of TZ, as the experiments did not cover sufficient time (of 4 to 7 days) for tolerance to develop. Therefore longer time for chronic TZ administration is used. We investigated the effects of TZ on motor activity and exploratory behavior using plus maze and open field. Three experiments were conducted. In the first, five groups of rats were acutely treated with different doses of TZ (0.25 mg/kg-4.0 mg/kg). In the second set of experiments, rats were treated chronically with a single daily dose of TZ (started with 0.25 mg/kg and increased by time to 1.0 mg/kg) for 5 weeks (representing clinical use). In the third, rats were treated chronically with three daily doses of TZ (started with 0.25 mg/kg and increased by time to 0.5 mg/kg) for 20 days (mimicking drug abuse). Acute TZ administration produced dose dependent anxiolytic effects and a decrease in motor activity with higher doses. Chronically treated rats, either once daily or three times daily doses, showed tolerance to both anxiolytic and sedative effects of TZ. It may be concluded that tolerance to the anxiolytic and sedative effects of TZ would develop after chronic administration either with clinical use or its abuse.     

Antinociceptive and gastroprotective effects of inhaled and orally administered Lavandula hybrida Reverchon "Grosso" essential oil

In this study the antinociceptive and the gastroprotective effects of orally administered or inhaled Lavandula hybrida Reverchon "Grosso" essential oil, and its principal constituents linalool and linalyl acetate were evaluated in rodents. Either when orally administered (100 mg/kg) or inhaled for 60 min lavender essential oil significantly reduced the acetic acid-writhing response in a naloxone-sensitive manner. In the hot plate test, analgesic activity observed after oil inhalation was inhibited by naloxone, atropine, mecamylamine pretreatment suggesting the involvement of opioidergic as well as cholinergic pathways. Regardless of the administration route and the experimental model used both linalool and linalyl acetate did not produce significant analgesic response. Oral or inhalatory treatment with analgesic doses of essential oil did not affect mice spontaneous locomotor activity. Concerning the gastric effects, lavender oil, linalool and linalyl acetate oral administration protected against acute ethanol-induced gastric ulcers but did not prevent indomethacin-induced lesions indicating no interference with arachidonic acid metabolic cascade. In conclusion, besides this gastroprotection, lavender oil reveals an interesting analgesic activity mainly relevant after inhalation, at doses devoid of sedative side effect, suggesting the interest for potential application of this oil in aromatherapy.     

Effects of chronic buspirone treatment on female mice exposed to the long-lasting psychoemotional influence

The effects of chronic treatment (30 days) with the 5-HT1A receptor partial agonist buspirone (0.05, 1 and 10 mg/kg i.p.) on the behaviour of C57BL/6J female mice exposed to long-lasting psychoemotional influence were studied. The influence involved forced living of each female with an aggressive male separated with a perforated transparent partition in the same cage and daily female's presence during 10-min intermale confrontations behind a partition caused by introducing of another male to the aggressive male. Chronic buspirone injection (in all used doses) did not affect the behaviour of females estimated in the "partitions" and "open field" tests at the end of the drug treatment. The anxiolytic effect of buspirone only at the dose of 1 mg/kg on the female's plus-maze behaviour was revealed. In the Porsolt, test buspirone in the dose of 1 mg/kg caused a slight increase in the duration of immobility indicating a slight pro-depressive effect. Thus, chronic buspirone treatment of females exposed to the long-lasting psychoemotional impact has a different effect on their behaviour depending on the dose and test conditions.     

Anxiolytic and anticonvulsant properties of doramectin in rats: behavioral and neurochemistric evaluations

Doramecin is an antiparasitic drug that may interfere with gamma-aminobutyric acid (GABA) neurotransmission. Some behavioral manifestations are related with GABAergic neurotransmissions as anxiety and seizures. The objective of the present study was to examine the possible central nervous system (CNS) effects of doramectin (100, 300 and 1000 microg/kg, SC) in rats, using anxiety behavioral models, susceptibility to seizures and central neurotransmitter evaluations. The open-field results showed (i) few alterations in locomotion frequency; (ii) a biphasic effect on rearing frequency that may be the consequence of least habituation in open-field; (iii) the reduction of grooming durations might be attributed to a possible anxiolytic effect of doramectin since GABAergic agonists reduced this parameter in apparatus. Our data in the hole board showed no effects in locomotion and rearing frequencies but increased head dipping frequency of rats administered doramectin similarly to anxiolytic drugs. In plus-maze test, doramectin administration increased the number of entries and time into open arms, indicating also an anxiolytic effect. Doramectin protected animals from convulsant effects of picrotoxin, indicative of an anxiolytic pharmacological profile of a drug with GABAergic properties. The alterations observed in central dopaminergic, noradrenergic and serotoninergic neurotransmissions might be the consequence of reinforcement in central GABAergic neurotransmission induced by doramectin. The present results suggest that doramectin has the pharmacological profile of an anxiolytic/anticonvulsant drug with GABAergic properties.     

Anxiolytic activity of Indian Abies pindrow Royle leaves in rodents: an experimental study

Putative anxiolytic activity of ethanolic extract of Indian A. pindrow Royle leaf was investigated in rats using various experimental paradigms of anxiety viz. open field exploratory behaviour, elevated plus maze (EPM) and elevated zero maze (EZM) tests. Pilot studies indicated that single dose administration of extract had little to no acute behavioural effects, hence the extract was administered orally at different dose levels once daily for three consecutive days, while lorazepam (LR) (0.5 mg/kg, i.p.) was administered acutely. Ethanolic extract of A. pindrow (AP) leaves (50 and 100 mg/kg, p.o.) showed significant anxiolytic effects on all the paradigms of anxiety. The results indicate that AP and LR induced a significant increase in open field ambulation and slight increase in rearings and activity in center, whereas grooming and faecal droppings remain unchanged. In EPM, significant augmentation of open arm entries, and time spent on open arms was noted in AP treated rats. In EZM test, significant increase in time spent on open arms and entries in open arms was observed, whereas slight increase in head dips and stretched attend postures was also observed. The AP extract showed consistent and significant anxiolytic activity in all the tests. The effects induced by ethanolic extract of AP were less marked than those of lorazepam were.     

Absence of anxiolytic response to chlordiazepoxide in two common background strains exposed to the elevated plus-maze: importance and implications of behavioural baseline

Although genetic background is acknowledged as a potentially important determinant of mutant phenotypes, publications on genetically modified mice far outnumber those on progenitor strains. We have recently reported major differences in basal anxiety levels (elevated plus-maze & light/dark exploration) among three strains (C57BL/6JOlaHsd, 129/SvEv and 129S2/SvHsd) employed as progenitor stock in European laboratories (Rodgers et al. in press). Furthermore, the phenotypes of these inbred strains differed significantly from that of an outbred strain (Swiss-Webster) commonly used in behavioural pharmacology. In view of these findings, the present study assessed possible differences in the anxiolytic efficacy of chlordiazepoxide (0, 7.5 & 15.0 mg/kg, IP) in three of these strains (Swiss-Webster (SW), C57BL/6JOIaHsd (C57) & 129S2/SvHsd (129)). Experimentally naive mice were exposed to the elevated plus-maze, sessions were videotaped and behaviour analysed using ethological software. The performance of control subjects confirmed significant strain differences in basal levels of activity (SW > C57 > 129) and anxiety-related behaviours (129 = SW > C57), with hypolocomotion dominating the 129 profile. SW mice displayed an anxioselective response to both doses of chlordiazepoxide (CDP), with significant reductions in open arm avoidance and risk assessment observed in the absence of any change in general activity. In direct contrast, the lower dose of CDP (7.5 mg/kg) was without effect in either inbred strain, whereas treatment with 15.0 mg/kg induced a profile indicative of muscle relaxation/mild sedation in C57 mice and virtually abolished all behavioural activity in 129 mice. Although the absence of an anxiolytic response to CDP in C57 mice may be attributed to their low basal anxiety levels, the profile of 129 mice strongly suggests an abnormality in benzodiazepine/GABAA receptor function. The implications of these findings for research on mutant mice are discussed.     

Anxiolytic activity of Indian Hypericum perforatum Linn: an experimental study

The putative anxiolytic activity of 50% ethanolic extract of Indian Hypericum perforatum (IHp) was investigated in rats using various experimental paradigms of anxiety viz. open field exploratory behaviour (OFB), elevated plus maze (EPM), elevated zero maze (EZM), novelty induced suppressed feeding latency (FL) and social interaction (SI) tests. Pilot studies indicated that single dose administration of IHp had little to no acute behavioural effects, hence the extract of IHp was administered orally at different dose levels once daily for three consecutive days, while lorazepam (LR) (0.5 mg/kg, i.p.) was administered acutely. IHp extract (100 and 200 mg/kg, p.o.) showed significant anxiolytic effects on all the paradigms of anxiety. The results indicate that IHp and LR induced a significant increase in open field ambulation and slight increase in rearings and activity in centre, whereas grooming and fecal droppings remain unchanged. In EPM, significant augmentation of open arm entries, open arm/closed arm entries ratio and time spent on open arms was noted in IHp treated rats. In EZM test, significant increase in time spent on open arms and entries in open arms were observed, whereas slight increase in head dips and stretched attend postures were also observed. IHp and LR significantly attenuated the novelty induced increase in feeding latency. IHp treated rats also showed significant increase in social interaction in the novel environment. The IHp extracts showed consistent and significant anxiolytic activity in all the tests. The effects induced by 50% ethanolic extract of IHp were less marked than those of lorazepam were.     

Involvement of opioidergic system of the ventral hippocampus, the nucleus accumbens or the central amygdala in anxiety-related behavior

In the present study, the influence of opioidergic system of the ventral hippocampus, the nucleus accumbens or the central amygdala on anxiety-related behaviour was investigated in rats. As a model of anxiety, the elevated plus maze which is a useful test to investigate the effects of anxiogenic or anxiolytic drugs in rodents was used. Bilateral microinjection of different doses of morphine (2.5, 5 and 7.5 microg/rat) into the ventral hippocampus or the nucleus accumbens increased the percentage of open arm time (%OAT) and open arm entries (%OAE) but not locomotor activity, indicating an anxiolytic response. However, intra-central amygdala administration of the opioid did not show any response. On the other hand, microinjection of a dose of naloxone into the ventral hippocampus (2 microg/rat) or the nucleus accumbens (1 microg/rat) increased open arm time (%OAT), but not open arm entry (%OAE) which may indicate an anxiolytic effect. Pre-treatment administration of naloxone (0.5, 1 and 2 microg/rat) reversed the anxiolytic effect of morphine (7.5 microg/rat) injected into the ventral hippocampus in a dose-dependent manner. A dose of the antagonist (1 microg/rat) also reduced the morphine response (2.5 microg/rat) when injected in the nucleus accumbens. In conclusion, it seems that the opioidergic system in the ventral hippocampus and the nucleus accumbens are involved in anxiety-related behaviors and the ventral hippocampus may be the main site of action of the anxiolytic properties of morphine.     

Dissociation between the Espinet and perceptual learning effects in flavour aversion conditioning

In three experiments rats were given pre-exposure to two compound flavours, AX and BX, the two compounds being presented for some subjects on alternate trials (the intermixed schedule) and, for others, in separate blocks of trials (the blocked schedule). After aversion conditioning with A (in Experiments 1 and 2), the inhibitory properties of B were tested using both retardation (Experiment 1) and summation tests (Experiment 2). The results failed to support the proposal [Anim. Learn. Behav. 23 (1995) 361] that B should acquire inhibitory properties in the intermixed condition (the "Espinet effect"). Experiment 3 demonstrated that generalisation to BX after conditioning with AX was attenuated by intermixed pre-exposure (a perceptual learning effect). This pattern of results challenges the hypothesis that inhibitory learning during intermixed pre-exposure to AX and BX can account for both the Espinet and the perceptual learning effects.     

The effect of collagen degradation products (CDP) on the central dopaminergic system

The effect of collagen degradation products (CDP I--molecular weight circa 3000 D and CDP II--molecular weight circa 1200 D) on the central dopaminergic system was studied. Differences in the action of both these fractions in the apomorphine stereotypy test were noted; CDP I administered to rats in a dose of 5 micrograms just before application of the drug inducing the stereotypy enhanced the stereotypic behaviour of the animals whereas a dose of 40 micrograms significantly inhibited such behaviour. CDP II, on the other hand, had no effect on this type of stereotypy. Both fractions given in doses of 15 and 40 micrograms enhanced the stereotypy induced by amphetamine. CDP I and CDP II (15 and 40 micrograms) administered 30 min before observation of the animals intensified the cataleptic action of haloperidol, whereas both fractions (CDP I and CDP II) when administered 45 min before observation reduced the catalepsy.     

Effects of methyl-eugenol administration on behavioral models related to depression and anxiety, in rats

Croton zehntneri (Cz) is a popular plant in Brazilian folk medicine. Recently, the use of its essential oil showed depressive activity response in the central nervous system (CNS). Chemical studies show that the main compound of this oil is the methyl-eugenol (ME). This work seeks to evaluate the ME activity in behavioral models of depression and anxiety, in the rat. Male rats (60 days old) were divided into four groups (n = 10) and treated with doses of 1.0, 3.0 and 10.0 ml/100 g body wt., v.o., of ME (experimental) and saline (control). One hour after treatment, they were observed in the forced swimming test and 15 min later in the open-field test. A decrease was observed in the immobility time during the forced swimming test for all experimental groups, in comparison with control group (C = 168.8 +/- 27.3; 1.0 microl = 139.1 +/- 23.5; 3.0 microl = 137.2 +/- 18.7 and 10.0 microl = 139.8 +/- 23.6). The open-field results showed no differences in comparison to the control group. The same was observed for social interaction, plus-maze and holeboard tests, suggesting no alterations in anxiety behavior. These data suggest that ME administration induced antidepressive CNS alterations, expressed by the smallest immobility in the swimming model, and not of a level able to alter motor and exploratory activity in the open-field. The absence of effects observed in the open-field can be a result of the experimental contingency, taking low anxiety levels. These data are in contradiction to observations with Cz essential oil in these models.     

Effects of non‐host plant odour on Meligethes aeneus during immigration to oilseed rape

The use of semiochemicals for the manipulation of the pollen beetle, Meliethes aeneus (Fabricius) (Coleoptera: Nitidulidae), is being investigated for potential incorporation into a push‐pull strategy for this pest, which damages oilseed rape, Brassica napus L. (Brassicaceae), throughout Europe. Previous laboratory behavioural studies using volatiles from non‐host plants showed that M. aeneus is repelled by the odour of lavender, Lavendula angustifolia Mill. (Lamiaceae), essential oil. This article reports on semi‐field and field trials to investigate this behaviour under more realistic conditions. Semi‐field experiments were conducted to assess the relative importance of olfaction at different points in host location behaviour by M. aeneus. The results showed that oilseed rape plants treated with lavender odour were less colonised by M. aeneus in comparison with an untreated control, but that the treatment effect was much reduced if the lavender odour was applied after colonisation. The field experiment demonstrated that lavender odour caused a significant reduction in the number of adult M. aeneus infesting the oilseed rape plants in the treatment plots compared to the control plots. Overall, these findings are very encouraging for the future development of a push‐pull pest control system.