Activation of DUM cell interneurons by ventral giant interneurons in the cockroach, periplaneta americana

Abstract

Dorsal unpaired median (DUM) cells in orthopteran insects are known to contain the neuromodulatory substance octopamine, and DUM cells with peripheral axons augment synaptic activity at neuromuscular junctions. One of the most studied systems in the cockroach is the giant interneuron (GI) system which controls the initial movements of a wind-mediated escape response. Our data demonstrate that DUM cells that are restricted to the central nervous system (DUM interneurons) receive inputs from ventral giant interneurons (vGIs) but not from dorsal giant interneurons (dGIs). In contrast, DUM cells that have peripheral axons consistently fail to be excited by any giant interneurons. The DUM interneurons are excited by vGIs on both sides of the CNS and, when the vGIs are excited in pairs, summation occurs. Wind fields that have been generated for two of the DUM interneurons are omnidirectional. These data, taken along with the known association of DUM cells with the neuromodulatory substance octopamine, suggest that the DUM interneurons may act to modulate central synapses.

Prothoracic DUM neurons of the cricket Gryllus bimaculatus ? responses to natural stimuli and activity in walking behavior

“…Although not conclusive, this investigation pointed to a possible direct and indirect connection of DUM cells with ascending interneurons of the abdominal cord. Pollack et al (1988) could not reveal any direct connection of DUMa type neurons in cockroach thoracic ganglia to giant interneurons transmitting cercal sensory information through the ventral nerve cord. These findings are compatible with an information transfer from the cerci to thoracic interneurons exciting the DUM cells.…”

“…Although it is not known whether or not the DUMc neurons we recorded from really contain and secrete octopamine, their behavioral role could depend on a comparable mechanism. Pollack et al (1988) also discuss a modulation of central synapses by local DUM neurons in the cockroach. Similar intraganglionic DUM cells, which lack any peripheral axons, possess relatively small somata and do not generate action potentials, have been demonstrated by Goodman et al (1980).…”

“…DUM dorsal unpaired median; DUMETi dorsal unpaired median neuron of the extensor tibiae muscle; SPL sound pressure level; TTL transistor-transistor logic the brain contain somata of a group of neurons with a characteristic morphology, the dorsal unpaired median (DUM) cells (locust : Plotnikova 1969;cockroach: Crossman et al 1971;cricket: Clark 1976; Davis and Alanis 1979). From a large cell body in the sagittal midline of the ganglion, a primary neurite gives rise to a pair of symmetrical lateral neurites, which either leave the ganglion through segmental nerves to innervate peripheral muscles (Hoyle 1978;Evans and O'Shea 1978) or run through inter-segmental tracts within the connectives (Arikawa et al 1984;Tanaka and Washio 1988) or remain completely intraganglionic (Goodman et al 1980;Pollack et al 1988). A common physiological feature of DUM neurons is a large action potential with hyperpolarizing afterpotential, which is evoked at a number of independent spike initiating regions and triggers an action potential also at the cell membrane of the soma (Heitler and Goodman 1978;Hoyle and Dagan 1978).…”

“…The continually growing body of data on the morphology, output connections and effects of DUM neurons in dissected preparations contrasts sharply with the very limited knowledge of the different stimulus modalities which influence these cells under normal conditions (Hoyle and Dagan 1978) and the neuronal paths which transmit this information (Pollack et al 1988). The present study addresses these questions for the DUM neurons in the prothoracic ganglion of the cricket, Gryllus bimaculatus.…”

Wasp venom injected into the prey's brain modulates thoracic identified monoaminergic neurons

“…This long latency response indicates that the wind sensory input is most probably not conveyed directly to the OA neurons in the thorax but may be conveyed through a polysynaptic connection via the brain. In support of this, Pollack et al (1988) showed that the GIs probably do not synapse directly onto the efferent OA neurons. Moreover, removing the brain nearly completely abolished the robust response of the OA neurons to wind.…”