Development of the gin trap reflex inManduca sexta: a comparison of larval and pupal motor responses
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Responses of motor neurons in larvae and pupae ofManduca sexta to stimulation of tactile sensory neurons were measured in both semiintact, and isolated nerve cord preparations. These motor neurons innervate abdominal intersegmental muscles which are involved in the production of a general flexion reflex in the larva, and the closure reflex of the pupal gin traps.
Larval motor neurons respond to stimulation of sensory neurons innervating abdominal mechanosensory hairs with prolonged, tonic excitation ipsilaterally, and either weak excitation or inhibition contralaterally (Figs. 4A, 6).
Pupae respond to tactile stimulation of mechanosensory hairs within the gin traps with a rapid closure reflex. Motor neurons which innervate muscles ipsilateral to the stimulus exhibit a large depolarization, high frequency firing, and abrupt termination (Figs. 2, 4B). Generally, contralateral motor neurons fire antiphasically to the ipsilateral motor neurons, producing a characteristic triphasic firing pattern (Figs. 7, 8) which is not seen in the larva.
Pupal motor neurons can also respond to sensory stimulation with other types of patterns, including rotational responses (Fig. 3 A), gin trap opening reflexes (Fig. 3 B), and ‘flip-flop’ responses (Fig. 9).
Pupal motor neurons, like larval motor neurons, do not show oscillatory responses to tonic current injection, nor do motor neurons of either stage appear to interact synaptically with one another. Most pupal motor neurons also exhibit i-V properties similar to those of larval motor neurons (Table 1; Fig. 10). Some pupal motor neurons, however, show a marked non-linear response to depolarizing current injection (Fig. 11).
KeywordsMotor Neuron Sensory Neuron Current Injection Nerve Cord Rotational Response
posterior branch of the dorsal nerve, resp
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- Bate CM (1972) Neuronal control and differentiation of a pupal reflex in sphingid moths. PhD thesis, Cambridge UniversityGoogle Scholar
- Bate CM (1973a) The mechanism of the pupal gin trap. I. Segmental gradients and the connexions of the triggering sensilla. J Exp Biol 59:95–107Google Scholar
- Bate (1973b) The mechanism of the pupal gin trap. II. The closure movement. J Exp Biol 59:109–119Google Scholar
- Bate CM (1973c) The mechanism of the pupal gin trap. III. Interneurones and the origin of the closure mechanism. J Exp Biol 59:121–135Google Scholar
- Bell RA, Joachim FA (1976) Techniques for rearing laboratory colonies of tobacco hornworms and pink bollworms. Ann Entomol Soc Am 69:365–373Google Scholar
- Booker R, Truman JW (1987) Postembryonic neurogenesis in the CNS of the tobacco hornworm,Manduca sexta. I. Neuroblast arrays and the fate of their progeny during metamorphosis. J Comp Neurol 255:548–559Google Scholar
- Heitler WJ, Burrows M (1977) The locust jump. I. The motor programme. J Exp Biol 66:203–219Google Scholar
- Kent KS, Levine RB (1988a) Neural control of leg movements in a metamorphic insect: sensory and motor elements of the larval thoracic legs inManduca sexta. J Comp Neurol 271:559–576Google Scholar
- Kent KS, Levine RB (1988b) Neural control of leg movements in a metamorphic insect: persistence of the larval leg motor neurons to innervate the adult legs ofManduca sexta. J Comp Neurol 276:30–43Google Scholar
- Levine RB (1986) Reorganization of the insect nervous system during metamorphosis. Trends Neurosci 9:315–319Google Scholar
- Levine RB (1989) Expansion of the central arborizations of persistent sensory neurons during insect metamorphosis: the role of the steroid hormone, 20-hydroxyecdysone. J Neurosci 9:1045–1054Google Scholar
- Levine RB, Truman JW (1982) Metamorphosis of the insect nervous system: changes in morphology and synaptic interactions of identified neurones. Nature 299:250–252Google Scholar
- Levine RB, Truman JW (1985) Dendritic reorganization of abdominal motoneurons during metamorphosis of the moth,Manduca sexta. J Neurosci 5:2424–2431Google Scholar
- Levine RB, Pak C, Linn D (1985) The structure, function and metamorphic reorganization of somatotopically projecting sensory neurons inManduca sexta larvae. J Comp Physiol A 157:1–13Google Scholar
- Levine RB, Truman JW, Linn D, Bate CM (1986) Endocrine regulation of the form and function of axonal arbors during insect metamorphosis. J Neurosci 6:293–299Google Scholar
- Levine RB, Waldrop B, Tamarkin DA (1989) The use of hormonally-induced mosaics to study alterations in the synaptic connections made by persistent sensory neurons during insect metamorphosis. J Neurobiol 20:326–338Google Scholar
- Matsumoto SG, Hildebrand JG (1981) Olfactory mechanisms in the mothManduca sexta: response characteristics and morphology of central neurons in the antennal lobes. Proc R Soc Lond B 213:249–277Google Scholar
- Pearson KG, Heitler WJ, Steeves JD (1980) Triggering of locust jump by multimodal inhibitory interneurons. J Neurophysiol 43:257–278Google Scholar
- Truman JW (1983) Programmed cell death in the nervous system of an adult insect. J Comp Neurol 216:445–452Google Scholar
- Waldrop B, Levine RB (1988) Interneurons involved in multisegmental reflexes in larvae and pupae of the mothManduca sexta. Soc Neurosci Abstr 14:1003Google Scholar
- Weeks JC, Jacobs GA (1987) A reflex behavior mediated by monosynaptic connections between hair afferents and motoneurons in the larval tobacco hornworm,Manduca sexta. J Comp Physiol A 160:315–329Google Scholar
- Weeks JC, Truman JW (1985) Independent steroid control of the fates of motoneurons and their muscles during insect metamorphosis. J Neurosci 5:2290–2300Google Scholar
- Weevers R DeG (1966) A lepidopteran saline: effects of inorganic cation concentrations on sensory, reflex and motor responses in a herbivorous insect. J Exp Biol 44:163–175Google Scholar