Innervation of the ventral diaphragm of the locust (Locusta migratoria)

Role of adenosine in functional recovery following anoxic coma in Locusta migratoria

When exposed to prolonged anoxia insects enter a reversible coma during which neural and muscular systems temporarily shut down. Nervous system shut down is a result of spreading depolarization throughout neurons and glial cells. Upon return to normoxia, recovery occurs following the restoration of ion gradients. However, there is a delay in the functional recovery of synaptic transmission following membrane repolarization. In mammals, the build-up of extracellular adenosine following spreading depolarization contributes to this delay. Adenosine accumulation is a marker of metabolic stress and it has many downstream effects through the activation of adenosine receptors, including the inhibition of cAMP production. Here we demonstrate that adenosine lengthens the time to functional recovery following anoxic coma in locusts. Caffeine, used as an adenosine receptor antagonist, decreased the time to recovery in intact animals and lengthened the time to recovery in semi-intact animals. A cAMP inhibitor, NKH 477, delayed recovery time in male animals. Our results show that the rate of recovery in insect systems is affected by the presence of adenosine.

Enhanced haemolymph circulation by insect ventral nerve cord: hormonal control byPseudaletia unipunctaallatotropin and serotonin

The ventral diaphragm (VD) in many insects is a muscular membrane that essentially partitions a perineural sinus from the rest of the abdomen. In the true armyworm moth Pseudaletia unipuncta (Lepidoptera: Noctuidae) we describe how the VD is characterized by a series of aliform muscles inserted into a tissue matrix that is fused to the dorsal surface of the ventral nerve cord (VNC) itself. Because of this arrangement, the abdominal VNC can attain high rates of lateral oscillation, and is capable of directing haemolymph flow. We have previously demonstrated Manduca sexta allatotropin(Manse-AT)-like immunoreactivity throughout the central nervous system (CNS)in P. unipuncta, and that both Manse-AT and serotonin (5-HT) are dose-dependent stimulators of the dorsal vessel. Here we describe both Manse-AT- and 5-HT-like immunoreactivity associated with the VD. Furthermore,both Manse-AT and 5-HT are dose-dependent stimulators of the rates of VNC oscillation, and together are capable of maintaining highly elevated rates of VNC oscillation for extended periods of time. These data indicate that both the dorsal vessel and the VD/VNC are similarly modulated by both Manse-AT and 5-HT, and that VNC oscillations play a more active role in overall haemolymph circulation than previously recognized.

Control of circulation in insects

1. Studies on the physiology of insect circulation have revealed that the insect central nervous system can exert a strong nervous control over certain dorsal vessels and diaphragms. 2. The function of neurohormonal control over the heartbeat of insects, though demonstrated, is less clear. In contrast with studies on the central nervous and skeletal neuromuscular systems, not one neurotransmitter substance has been identified in any of the vessels, pumps or diaphragms responsible for circulation in insects. 3. A coelopulse system was identified and described that suggested a very sophisticated coordination between circulation and respiration in insects. The circulatory systems of cockroach, locust, fly, moth and bee all involve unique specializations. 4. It is suggested that an autonomic nervous system is present in insects and is responsible for coordination and control of both circulation and respiration.

Suction capillaries with U-shaped opening for holding moving cells during intracellular electrical recording

The production of suction capillaries with an U-shaped cross-section is described. The capillary may be used for holding contractile cells during intracellular recording to diminish movement artifacts. In addition microelectrode penetration is facilitated by stretching the surface of the cell.

Motor innervation of the pharynx levator muscle of the snail, Helix pomatia: physiological and histological properties

(1) Motor innervation of the pharynx levator muscle of Helix pomatia was investigated with intracellular recording and axonal iontophoresis of cobalt chloride. (2) Muscle fibers respond to direct electrical stimulation of the muscle with active graded responses or non-overshooting spike potentials. (3) Each fiber is innervated via the external and internal lip nerves by several (mostly 3) excitatory nerve fibers each. Two types of EPSPs can be distinguished according to amplitude, duration, and facilitation. (4) Axonal CoCl2-staining via an external lip nerve branch revealed many nerve fibers entering the muscle and branching there into a rich network of blebbed fibers of various diameters.