GENERAL AND COMPARATIVE ENDOCRINOLOGY 45, 175- 180 (1981) Octopamine and Short-Term Hyperlipaemia in the Locust I. ORCHARD, B. G. LOUGHTON, AND RODNEY A. WEBB Department of Biology, York University, 4700 Keele Street, Downsview, Ontario, M3J IP3, Canada Accepted January 28, 1981 The response of locusts to experimental handling has been examined. “Excitation” in- duced by handling resulted in an elevation of both hemolymph octopamine and hemolymph lipid levels. Octopamine levels rose within 2 min, while protein-bound lipid rose within 5 min. Both responses followed a similar time course with the levels falling between 1 and 2 hr following excitation. Lipid levels did not return at this time in neck-ligated locusts but remained high. The excitation induced hyperlipaemia was reduced by injection of the CX- adrenergic blocking agent phenoxybenzamine. Injection of octopamine potentiated hyper- lipaemia in neck-ligated locusts. The possibility of a cause-and-effect relationship between octopamine levels and lipid levels is discussed. The elevation of hemolymph lipid levels in the locust has been shown to be under the control of adipokinetic hormone (AKH), which is released from the glandular lobe of the corpus cardiacum (CC) (see review by Stone and Mordue, 1980). This hyperli- paemia normally occurs in response to the demands of flight and persists over a pro- longed time period (Jutsum and Golds- worthy, 1976). An analogous elevation of hemolymph sugars has been observed in the cockroach in response to injection of extracts of the CC (Steele, 1961). However, Matthews and Downer (1974) showed that hemolymph trehalose levels in the cock- roach also increased in response to stress. This response was maximal after 15 min but was detectable during the first hour after excitation. Subsequently Downer (1979) showed that the response was independent of the presence of the CC and termed the phenomenon excitation induced hyper- trehalosaemia (EXIT response). After in- jecting several biogenic amines and their antagonists into neck-ligated cockroaches, Downer (1979) proposed that the EXIT response was mediated by octopamine. Gole and Downer (1979) demonsrated in- creases in adenosine 3’5’-monophosphate (cyclic-AMP) levels in cockroach fatbody in vitro together with the release of treha- lose after incubation with octopamine. It was suggested from this work that the EXIT response may be mediated by a direct action of octopamine upon the fat- body. Octopamine has been shown to be pres- ent in hemolymph of lobsters (Livingstone et al., 1980) and locusts (David and Lafon-Cazal, 1979). Recently Goosey and Candy (1980) have demonstrated an in- crease in octopamine at the initiation of flight in locusts. The possibility that oc- topamine acts as a hormone is implied by the observations that octopamine is re- leased from neurohemal tissue into the he- molymph of lobsters (Evans et al., 1976) and that octopamine is associated with neurohemal tissue in insects (see Dymond and Evans, 1979). However, for a clearer understanding of the role of octopamine in stress-induced physiological changes it is essential to examine any stress-induced changes in hemolymph octopamine levels. We have examined the changes in hemo- lymph lipid and octopamine levels in the locust following excitation induced by han- dling and injection of saline. We have also examined the effects of injection of oc- topamine, an a-adrenergic blocking agent, 175 0016~6480/81/100175-06$01.00/O Copyright @ 1981 by Academic Press, Inc. All rights of reproduction in any form reserved.