Developmental study of the Proboscis Extension Response to heat in Rhodnius prolixus along the life cycle.

Triatominae are blood-sucking insects that localise their hosts using a range of sensory signals to find food, and among them, the heat emitted by the hosts. Heat is one of the main short-range cues in vertebrate hosts, able to trigger alone the Proboscis Extension Response (PER) that precedes the bite. Previous studies demonstrated that heat responsiveness of fifth-instar nymphs is maximum to moderate temperatures (30-35°C) compatible with those of their vertebrate host's body surface.

Daily variation of the response to heat in Rhodnius prolixus: the roles of light and temperature as synchronisers.

Triatominae are blood-sucking insects that localise their hosts with their multimodal host associated perceptive signals. Among that sensory information, one of the main short-range cue is heat which, even in isolation, is able to trigger the Proboscis Extension Response (PER) preceding the bite. Previous studies have demonstrated a rhythmic variation of the response to host signals compatible with the nocturnal habits of triatomine insects.

Response to heat in Rhodnius prolixus: the role of the thermal background.

Heat is the principal host-associated cue for the blood-sucking bug Rhodnius prolixus. It is both necessary and sufficient to trigger the "proboscis extension response" (PER), an essential element of the feeding behaviour of this insect. The aim of this study was to determine whether the temperature of an object itself or the thermal contrast between the object and the environmental background is responsible for triggering the PER.

Antennal pathways in the central nervous system of a blood-sucking bug, Rhodnius prolixus.

The haematophagous bug Rhodnius prolixus has been a model system in insect physiology for a long time. Recently, several studies have been devoted to its sensory systems, including olfaction. However, few data are available on the basic organisation of the nervous system in this species.

Adrenergic drugs modify the level of noradrenaline in the insular cortex and alter extinction of conditioned taste aversion in rats.

We compared the effect of conditioned taste aversion in rats by measuring the amount of sucrose that they drunk after conditioning, which differed according to whether rats had drunk the sucrose freely (SD: self drinking) during the conditioning session, or had been forced to drink it (IO: intra-oral administration through a chronically implanted cannula). The SD procedure delayed the extinction of conditioned taste aversion. Enhanced arousal, alertness, awareness or attention in the SD condition may have strengthened the memory of the taste.

Insular cortex lesions alter conditioned taste avoidance in rats differentially when using two methods of sucrose delivery.

The insular gustatory cortex may be essential for the evaluation of saliency and representation of the incentive values of tastes. Gustatory cortex lesions should interfere with conditioned taste avoidance according to these factors, which depend on the conditioned taste avoidance protocol used. The present study was aimed at investigating the effects of bilateral lesions of the gustatory cortex-focusing on electrolytic and excitotoxic lesions.

Frontal lesions do not alter the differential extinction of taste aversion conditioning in rats, when using two methods of sucrose delivery.

The frontal cortex is involved in the planning of behavioural responses and in the processing of their outcomes. Thus it contributes to several learning mechanisms, including those of conditioned taste aversion (CTA). A solution of sucrose drunk freely by a rat from a drinking tube-self-drinking protocol (SD)-was used as a conditioned stimulus in CTA.

Conditioned taste aversion using four different means to deliver sucrose to rats.

A solution of sucrose either to be drunk from a drinking tube-self-drinking procedure (SD)-or perfused intraorally as a consequence of nose-pokes-self-administration procedure (SA)-or perfused as a consequence of licking an empty tube (LA)-was paired with an LiCl-induced malaise in rats. The effects were compared to those of a procedure consisting of intraoral administration (IO) of sucrose not contingent to any specific action of the rat. Similar levels of conditioned taste aversion (CTA) were obtained but extinction in the IO procedure was quicker than in the SA procedure, which was itself quicker than in the SD procedure.

Effects of aging on the acquisition and extinction of excitatory conditioning in Drosophila melanogaster.

Young (7-day-old), middle-aged (28-day-old), and old (49-day-old) Drosophila melanogaster were compared for acquisition, then extinction, of excitatory conditioning of the Proboscis Extension Response. The contribution of nonassociative processes (sucrose-induced Central Excitatory State, Pseudoconditioning) in the elicitation of conditioned responses was simultaneously assessed. Old flies displayed a faster and stronger acquisition than middle-aged ones, whereas no significant acquisition was stated in young flies.

A new attempt to assess the effect of learning processes on the cholinergic system: studies on fruitflies and honeybees.

The effect of training on the functioning of the cholinergic system was investigated in fruitflies and in honeybees. Drosophila were submitted to a passive avoidance conditioning of the proboscis extension response (PER). Flies had to learn to suppress the sugar-induced PER to avoid an aversive quinine reinforcement.

Spontaneous locomotor activity of Drosophila melanogaster flies at various gravity levels (0 g, 1 g, 1.8 g) during parabolic flights.

The spontaneous locomotor activity of young, middle-aged and old Drosophila melanogaster of both sexes has been videorecorded during three parabolic flights separated by one-day intervals. Fast shifts between 0 g, 1 g and 1.8 g phases are obtained during parabolic flights.

Effects of ageing on visual discrimination learning in Drosophila melanogaster.

Two experiments examined conditioned suppression of the Proboscis Extension Response (PER), unconditionally released by sucrose stimulation of gustatory tarsal receptors, in young (7-day-old), middle-aged (30-day-old) and old (50-day-old) Drosophila melanogaster males, reared at 25 degrees C. Individual flies were trained in a differential conditioning procedure in which a white stimulus signalled a quinine reinforcer, whereas a black stimulus was non-reinforced. When trained from the outset with the discriminative procedure, flies of all ages acquired the discrimination, although the acquisition of PER suppression to the white stimulus was retarded in middle-aged and old flies.

Hypergravity, aging and longevity in Drosophila melanogaster.

1. Drosophila melanogaster flies have been used in studies of the effect of hypergravity (HG) on aging and longevity. 2.