Tatsuaki Shibuya

Morphological and physiological properties of pheromone-triggered flipflopping descending interneurons of the male silkworm moth, Bombyx mori

Abstract1.The morphology of descending interneurons (DNs) which have arborizations in the lateral accessory lobe (LAL) of the protocerebrum, the higher order olfactory center, and have an axon in the ventral nerve cord (VNC), were characterized in the male silkworm moth, Bombyx mori.2.Two clusters (group I, group II) of DNs which have arborizations mainly in the LALs were morphologically characterized. The axons of these DNs are restricted to the dorsal part of the each connective (Figs. 1–5).3.Pheromonal responses of the group I and group II DNs were characterized. Flipflopping activity patterns, which have two distinct firing frequencies (high and low) in response to sequential pheromonal stimulation, were usually recorded (Figs.6–10).4.Two types of flipflopping activity patterns were classified into those that had an antiphasic relationship (called the ‘FF’ type) between the left and right connectives and those with a synchronized relationship (‘ff’ type) (Figs. 8–12). We propose that some group II DNs show ‘FF’ flipflopping activity patterns (Fig. 10).5.A state transition was usually elicited by less than 10 ng bombykol, the principal pheromone component. Extra impulses were elicited during constant light stimulation (Fig. 9).6.Our results suggest that the LAL olfactory pathways might be important for producing flipflopping activity patterns (Fig. 11).

Descending protocerebral neurons related to the mating dance of the male silkworm moth

Descending protocerebral neurons in the male silkworm moth brain responding to the sexual pheromone (Bombykol) were identified. The neurons responded well with a tonic type of response and the high-frequency spikes evoked continued even after the end of the stimulus. Characteristics of the dose-response curves of the neurons to the pheromone remarkably resembled those of the wing vibration which is one of the mating behavioral components of the male moths.

Long-lasting excitation of protocerebral bilateral neurons in the pheromone-processing pathways of the male moth Bombyx mori

Intracellular recording and staining with Lucifer yellow were used to characterize the responses and structure of pheromone-processing bilateral neurons in the protocerebrum of the brain of the male silkworm moth Bombyx mori. Numerous olfactory bilateral neurons innervated a particular neuropil region lateral to the central body, the lateral accessory lobe (LAL). The LALs are linked to each other by bilateral neurons with arborizations in each LAL. The LAL appears to be important for collecting the olfactory information from both sides of the brain. Many of the bilateral neurons showed a characteristic long-lasting excitation (LLE) that outlasted the olfactory stimuli (1.5 s). In some preparations, the LLE lasted more than 20 s and the firing gradually decreased to the background level.

PHYSIOLOGY AND MORPHOLOGY OF OLFACTORY NEURONS ASSOCIATING WITH THE PROTOCEREBRAL LOBE OF THE HONEYBEE BRAIN

Physiology and morphology of olfactory neurons associated with the protocerebral lobe around the alpha-lobe of the mushroom body were studied in the brain of the honeybee Apis mellifera using intracellular recording and staining techniques. The responses of neurons to behaviorally relevant odorants (a blend, and components of the Nasonov pheromone, and some other non-pheromonal odors) were recorded. Different response patterns were observed within different neurons, and often within the same neuron, in response to different stimuli. All the neurons stained had innervations in the protocerebral lobe. The cell profiles varied from cells connecting the antennal lobe with both the protocerebral and lateral protocerebral lobes (projection neurons), cells linking the pedunculus of the mushroom body with both the protocerebral and lateral protocerebral lobes (PE1 neurons), cells linking the alpha-lobe and protocerebral lobe with the calyces of the mushroom body (feedback neurons), and cells linking the alpha-lobe and protocerebral lobe with the antennal lobe (recurrent neurons), to cells connecting the protocerebral lobe with the contralateral protocerebrum (bilateral neurons). These findings suggest that the protocerebral lobe acts as an olfactory center associating with other centers, and provides multi-layered recurrent networks within the protocerebrum and between the deutocerebrum and the protocerebrum in honeybee olfactory pathways.

Responses of single olfactory receptor cells to sex pheromones in the tobacco cutworm moth, Spodoptera litura

Abstract A single olfactory receptor cell of the male tobacco cutworm moth was recorded at the basal region of the sensillum trichodeum and its response to pheromones. Low frequency impulses were recorded from the olfactory receptor to compound A alone. Stimulation with a mixed ratio (9:1) of compound A and compound B increased the frequency of impulses more than compound A alone. However, increase of compound B in the ratio (5:5, 1:9) reduced gradually the frequency of impulses. Stimulation by compound B alone was without effect. It appears that the synergistic effect probably involve mechanisms at the level of the olfactory receptor cell.

Action of some drugs on gecko olfactory bulb mitral cell responses to odor stimulation

The probable relationships of neural connectivity of the olfactory bulb have been established in morphologicaP, 12 and evoked-potential studies 11,1~,1a,19. There are a few descriptions of the mitral cell activity in response to odor stimulation 4,5,7,17,1s. In general, the effect of odor presentation to the pr imary neurons on the mitral cell activity could be described as excitation, suppression or null 4. However, effects of drugs on the odor-evoked electrical response of the mitral cell have not been reported. This study is a preliminary report on the effects of some drugs on the excitation type of odor-evoked response of the mitral cell. Effects of some drugs on the suppression type of response to odor will be reported elsewhere. The drugs were applied locally by iontophoresis from microelectrodes or extensively by perfusion of solutions over the exposed olfactory bulb. Adult geckos (Gekko gecko) were anesthetized with urethane. The head of the gecko was fixed in a holder, the olfactory bulbs were exposed and a shallow pool was formed to direct a continuous flow of reptilian Ringer over them. Procian brown or Fast Green dye permeated from the surface into the external plexiform layer within 3 min as shown by histological examination of paraffin sections. For the perfusion method, 7-aminobutyric acid (GABA), carnosine and bicucultine were made up as 10 -3 M solutions in Ringer and exchanged for the Ringer flowing continuously at about 0.04 ml,sec over the bulbar surface. In the electrophoretic method, glass microelectrodes were filled with GABA (0.5 M, pH 3) or carnosine (0.25 M, pH 7). Two electrodes were mounted in a holder with their tips separated vertically by about 200 #m, so that when the upper one was positioned in the glomerular layer (GL) the lower one was in the external plexiform layer (EPL) about 400 #m below the surface. The recording microelectrode was inserted adjacent to the tip of an electrophoresis electrode. Electrode positions were usually selected by the field potential method 11,1~ and in some instances confirmed by means of dye deposition. Conventionalextracellular

Induced wave responses of the accessory olfactory bulb to odorants in two species of turtle, pseudemys scripta and geoclemys reevesii

Abstract 1. 1. Induced wave responses of the accessory olfactory bulb to various chemical stimuli applied to the vomeronasal mucosa were recorded on two species of aquatic turtles. 2. 2. Vapor stimuli and aqueous stimuli yielded responses in either or both turtles. 3. 3. Stimulants to which turtles responded well were different in the two species. 4. 4. Single electrical stimulation delivered to the vomeronasal nerve caused oscillatory potential responses similar to those caused by odor stimulation.

Distribution and fine structure of antennal olfactory sensilla in Japanese dung beetles, Geotrupes auratus Mtos. (Coleoptera : Geotrupidae) and Copris pecuarius Lew. (Coleoptera : Scarabaeidae)

Abstract The distribution and fine structure of olfactory sensilla on the antennal flagella of the Japanese dung beetles, Geotrupes auratus (Coleoptera : Geotrupidae) and Copris pecuarius (Coleoptera : Scarabaeidae) were studied by scanning and transmission electron microscopy. In both types of dung beetles, sensilla on the antennal segments were most abundant on the apical 3 lamellar segments, where sensilla basiconica were particularly concentrated. The sensilla were solely concentrated in the central part of the distal side of both the 9th and 10th segments in G. auratus and the 7th and 8th segments in C. pecuarius , respectively. The numbers of sensilla in these areas (channels) of the 9th and 10th segments in G. auratus were approximately 4,500 and 3,000, respectively. In C. pecuarius , there were about 1,900 sensilla on the 7th segment and l,700 sensilla on the 8th. The cuticles of the sensilla in both species were perforated by numerous elongate pores, with a pore density of about 45/ μm 2 in G. auratus and 30/ μm 2 in C. pecuarius . Each sensillum basiconicum in C. pecuarius was generally associated with 2 sensory neurons. The sensory cilia passed into the sensillum lumen and branched profusely, occupying most of its space. On the basis of the fine structure and dense location, these sensilla are considered to have an olfactory function for food detection.

Olfactory responses to the sex pheromone component and its behavioural inhibitor in the male cigarette beetle, Lasioderma serricorne

Abstract Electroantennogram and single sensillum recordings were performed on the male cigarette beetle, Lasioderma serricorne , antennae. Strong antennal responses were elicited by not only natural sex pheromone component (4S,5S,7S)-serricornin (SSS-serricornin) but also non-natural behavioural inhibitor, (4S,5S,7R)-serricornin (SSR-serricornin). In the case of mixture application of the SSS- and SSR-serricornin, integrated electroantennogram responses were observed. Single sensillum recording from male flagella sensilla showed that the majority of basiconic type sensilla responded to the behavioural inhibitor as well as to the sex pheromone. However, a few of them responded only to the inhibitor. The behavioural inhibitory action of SSR-serricornin toward the SSS-serricornin results from central integration of the information from separate receptor cells rather than blockage at the peripheral receptors.

The effect of some drugs on the mitral cell odor-evoked responses in the gecko olfactory bulb

The activity of odor-evoked olfactory mitral cell response of the gecko was recorded extracellularly by glass microelectrodes. The activities of the mitral cell observed during the presentation of the odor (n-amyl acetate) could be described as excitation, suppression or zero. The present experiments were undertaken to study the neural activities of the mitral cell in the olfactory bulb by perfusion application of some drugs (cobalt chloride, carnosine, norepinephrine, GABA and D-L-homocysteate) on the olfactory bulb surface or iontophoretic application of some drugs (carnosine, norepinephrine, GABA and D-L-homocysteate) to the glomerulus and the external plexiform layer to change the physiological environment. The effect of the drugs suggested that the synaptic neurons on the mitral cell have different chemical characteristics.