Photoperiod cues and the modulatory action of octopamine and 5-hydroxytryptamine on locomotor and pheromone response in male gypsy moths,Lymantria dispar

Experiments were conducted to determine whether the biogenic amines octopamine (OA) and 5-hydroxytryptamine (5-HT) exert modulatory effects on pheromone responsiveness and random locomotor activity in male gypsy moths. When injected into males, OA significantly enhanced sensitivity to pheromone, while 5-HT enhanced general locomotor activity, results that were very similar to those previously shown for the cabbage looper. Maximal effect of the amines, however, was observed when injection occurred just prior to the onset of scotophase, rather than photophase, as we had originally hypothesized for this diurnally active insect. Male gypsy moths also displayed a prominent scotophase response, with sensitivity to pheromone greater in the scotphase compared with photophase, but with the level of random locomotor activity lower in scotophase than in photophase. The upwind flight behavior of males to a pheromone source in a wind tunnel, as well as the time spent at the source, were also significantly different in the two light regimes. Furthermore, when exposed to a 1 h scotophase (instead of the normal 8), or to continuous dark conditions, while males exhibited response to pheromone and locomotor activity during the same scotophase and photophase periods as observed in a 16:8 light : dark cycle, the levels of response, as well as qualitative aspects of the upwind flight behaviors in both periods were a function of the light intensity. Our combined results suggest that male gypsy moths display a bimodal rhythm of locomotor and pheromone response over the diel cycle, with light intensity and scotophase onset providing critical cues for the expression of behaviors, as well as the modulatory action of the amines. © 1992 Wiley-Liss, Inc.     

Selective modulation of task performance by octopamine in honey bee (<Emphasis Type="Italic">Apis mellifera</Emphasis>) division of labour

Octopamine treatment has previously been shown to increase honey bee foraging behaviour. We determined the effects of octopamine on other tasks to learn how octopamine affects division of labour in honey bee colonies. Octopamine treatment did not increase the rate of corpse removal from the hive, suggesting that elevated brain levels of octopamine do not act to increase the performance of all flight-related tasks. Octopamine treatment also did not increase attendance in the queen's retinue, suggesting that elevated brain levels of octopamine do not act to increase responsiveness to all olfactory stimuli. Consistent with these findings, octopamine treatment enhanced the foraging response to brood pheromone but not the cell capping response, a component of brood care. These results demonstrate a relatively specific form of neuromodulation by octopamine in the regulation of division of labour in honey bee colonies.     

Environmental regulation of female calling and male pheromone response periodicities in the codling moth (Laspeyresia pomonella)

Codling moth female calling and male pheromone responsiveness under the defined conditions of 23°C and light:dark (LD) 16:8 occurred primarily during scotophase. Under either continuous photophase or scotophase females called with periodicities very similar to their periodicity under the LD cycle, indicating that the rhythmicity is circadian. Male response rhythmicity was maintained under continuous photophase. A decrease in the temperature from 23° to 16°C resulted in a reduction in the proportion calling when the decrease in temperature occurred during scotophase and a shift of maximal calling into photophase when the decrease in temperature occurred 3 hr prior to the initiation of scotophase. Decreases of temperature from 23° to 16°C and of light intensity did not produce similar shifts in the periodicity of male upwind orientation. Of 6 pheromone dosages from 10^?5 to 10² μg, 10^?1 and 10⁰ μg elicited the most male upwind orientation.     

Biogenic amines modulate olfactory receptor neurons firing activity in Mamestra brassicae

The modulatory effects of the biogenic amines octopamine and serotonin on pheromonal receptor neurons of Mamestra brassicae were investigated. The responses to sex pheromone components of two cells types (A and B) in single male long sensilla trichodea were monitored. Cell types A and B do not respond to the same compound. The response of type A to a pulse of the major sex pheromone component increased 5 min after octopamine injection. Responses of type B to other odorants increased after 30 min. In the absence of any pheromone stimulation the background firing activity of type A increased following octopamine injection. This background activity was used to evaluate the kinetics of octopamine and other biogenic amine effects on olfactory receptor neurons. Octopamine increased this background activity in a concentration- and time-dependent manner. Clonidine, an octopamine agonist, was shown to be more powerful in increasing the background activity of olfactory receptor neurons. The effects of octopamine and clonidine were hypothesized to arise from specific receptor activation as chlorpromazine (an octopamine antagonist) was shown to block the effect of octopamine. Serotonin, a known neuromodulator in most animal species, induced a reversible inhibition of spike firing. Altogether, these results indicate that biogenic amines can modulate the sensitivity of olfactory receptor neurons of moths either directly or by an action on adaptation.     

Octopamine and tyramine modulate pheromone-sensitive olfactory sensilla of the hawkmoth <Emphasis Type="Italic">Manduca sexta</Emphasis> in a time-dependent manner

In moths octopamine improved pheromone-dependent mate search time dependently. In the nocturnal hawkmoth Manduca sexta long-term tip recordings of trichoid sensilla were performed to investigate whether biogenic amines modulate pheromone transduction time dependently. At three Zeitgebertimes octopamine, tyramine and the octopamine antagonist epinastine were applied during non-adapting pheromone-stimulation. At ZT 8-11, during the photophase, when sensilla were adapted, octopamine and to a lesser extent tyramine increased the bombykal-dependent sensillar potential amplitude and initial action potential (AP) frequency. In addition, during the photophase, when sensilla are less able to resolve pheromone pulses, octopamine rendered pheromone responses more phasic and sensitive, and raised the spontaneous AP frequency. During the late scotophase, at ZT 22-1, when the antenna appeared maximally sensitized for pheromone pulse detection and endogenous octopamine levels are high, exogenously applied octopamine was ineffective. Epinastine blocked the pheromone-dependent AP response at ZT 8-11 and slightly affected it at ZT 22-1, while it had no effect on the sensillar potential amplitude. Epinastine decreased the spontaneous AP activity during photophase and scotophase and rendered pheromone responses more tonic in the scotophase. We hypothesize that the presence of octopamine in the antenna is obligatory for the detection of intermittent pheromone pulses at all Zeitgebertimes.     

Physiological Mechanisms of Pheromonostatic Responses: effects of Adrenergic Agonists and Antagonists on Moth (Helicoverpa armigera) Pheromone Biosynthesis

The adrenergic agonists octopamine, tyramine and clonidine inhibited the normal pheromonotropic action due to PBAN (pheromone biosynthesis activating neuropeptide) in incubations of intersegmental tissues that are situated between the 8th and 9th abdominal segments of the moth ovipositor tip. This inhibition was reversed in the presence of the adrenergic antagonists phentolamine, yohimbine and chlorpromazine. Incubations of 8th segments alone, which do not produce pheromone, resulted in elevated levels of intracellular cAMP in the presence of octopamine. The physiological significance of this phenomenon is unclear. However, clonidine (an alpha(2) selective agonist) did not duplicate octopamine stimulation of intracellular cAMP in 8th segment cultures. In intersegmental membrane cultures clonidine successfully duplicated the octopamine inhibition of both pheromone and intracellular cAMP production. The physiological significance of octopaminergic receptors mediating the inhibitory response of intersegments was investigated by experiments in vivo. When PBAN was injected into photophase females the normal pheromonotropic activity due to the injected PBAN dropped after 2h. In the presence of clonidine, normal peak stimulatory levels were never attained and a faster decline was observed. Clonidine also inhibited the pheromonotropic response of 24h-decapitated females to PBAN. Adrenergic antagonists successfully reversed the inhibitory effect of clonidine in decapitated females, but did not reverse the effect of clonidine in photophase females. In addition, when clonidine was injected into female moths during the scotophase normal peak pheromone titers were reduced although no effect on calling behavior was observed. Copyright 1997 Elsevier Science Ltd. All rights reserved     

The circadian rhythm of flight activity of Spodoptera exigua males in response to sex pheromone

In many moths, male attraction to the blend of synthetic sex pheromone releasing continuously in the field shows an apparent circadian rhythm similar to that of locomotion activity. In this study, the daily rhythms of electroantennography (EAG) and behavioral responses to sex pheromone, and the daily rhythms of locomotion activity were measured in male beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). The peaks of males trapped by light and sex pheromone were all during the latter part of the night in the field. However, there was no significant variation among time intervals in the EAG responses of male antennae to sex pheromone stimuli. The principal period of locomotion activity under L15:D9 (LD) continued to occur during the scotophase and the subjective scotophase in the day of constant darkness (DD1) and the second of two consecutive days of constant darkness (DD2). The majority of males contacted the sex pheromone source in a wind tunnel during the latter part of the scotophase under LD and the subjective scotophase for DD1 and DD2. There were significant associations between the rhythm of the behavioral response to sex pheromone and locomotion activity. These results suggested that the male's behavioral response to sex pheromone in the beet armyworm could be observed only until locomotion activity of the male occurred at the end of the dark period, despite sex pheromone being released continuously from synthetic pheromone‐baited traps in the field.     

Octopamine modulates the sensitivity of silkmoth pheromone receptor neurons

Effects of octopamine and its antagonist epinastine on electrophysiological responses of receptor neurons of Antheraea polyphemus specialised to the pheromone components (E,Z)-6,11-hexadecadienyl acetate and (E,Z)-6,11-hexadecadienal were investigated. Injections of octopamine and epinastine into the moths had no effect on the transepithelial potential of the antennal-branch preparation nor on the spontaneous nerve impulse frequency in either type of receptor neuron. However, in the presence of continuous low-intensity pheromone stimulation, octopamine significantly increased the nerve impulse frequency in the acetate receptor neuron, but not in the aldehyde receptor neuron. Octopamine and epinastine had no significant effect on the receptor potential amplitudes elicited in both receptor neuron types by pheromone stimulation. However, the peak nerve impulse frequency in the response of both receptor neuron types to pheromone was significantly affected: decreased by epinastine and increased by octopamine over a broad range of pheromone concentrations. In control experiments, injection of physiological saline did not significantly alter the peak nerve impulse frequency. The effect of octopamine was established within 1 h after injection and persisted for about 4 h. The possibility of a direct action of octopamine on the nerve impulse generation by the receptor neurons is discussed. Accepted: 8 January 2000     

Endogenous control of circadian rhythms of pheromone production in the turnip moth, Agrotis segetum

The circadian variation of pheromone production in the turnip moth, Agrotis segetum, was characterized by quantifying (Z)-7-dodecenyl acetate (Z7-12:OAc), the most abundant pheromone component produced by female turnip moth, at different times of day. Under 17:7 h light-dark cycle (LD), the peak of Z7-12:OAc production occurred around 4 h into the scotophase, while there was very little pheromone production during the photophase. When females were maintained under constant darkness (DD), the periodicity of pheromone production was sustained for 3 consecutive days. Furthermore, the rhythm in pheromone production could be entrained to a shifted LD. These results demonstrate that the pheromone production in the turnip moth is regulated endogenously by a circadian clock. To understand how the circadian rhythm of pheromone production is generated, circadian variation of pheromone- biosynthesis-activating neuropeptide (PBAN)-like activity in the brain-suboesophageal ganglion complexes (Br-SOG), hemolymph, and ventral nerve cord (VNC) was also examined. Under both LD and DD, only the VNC displayed a circadian variation in the PBAN-like activity, which was significantly higher during the late-photophase than that in the scotophase. In addition, the present study showed that removal of VNC in isolated abdomen did not affect PBAN stimulation of pheromone production, while severing the VNC impaired normal pheromone production. The role of Br-SOG, VNC, and hemolymph in the regulation of the periodicity of pheromone production is discussed.     

Sublethal effects of neuroactive compounds on pheromone response thresholds in male oriental fruit moths

The pheromone-mediated flight behavior of male Oriental fruit moths in a sustained-flight tunnel was observed after males were treated topically with sublethal concentrations of permethrin, carbaryl, chlordimeform, dieldrin, octopamine, serotonin, yohimbine, and cyproheptadine. With the exception of serotonin all compounds were found to disrupt one or more specific elements of the male precopulatory flight sequence. Among the insecticides, dieldrin was least active, whereas permethrin, carbaryl, and chlordimeform induced unique effects at specific phases of the sequence. Octopamine induced a hypersensitivity to the olfactory signal and mimicked one of the effects observed with chlordimeform. Yohimbine and cyproheptadine significantly decreased moth activation to the chemical signal but did not alter flight performance in responding moths. Yohimbine and cyproheptadine also reversed the effects induced by octopamine. The results of our study show that the complex precopulatory sequence of behaviors exhibited by males is very sensitive to sublethal concentrations of a range of neuroactive compounds.     

Diel changes in the presence and physiological actions of octopamine in the female sex-pheromone glands of heliothine moths

Recent evidence suggests that the biogenic monoamine octopamine (OA) may be involved in the regulation of female sex-pheromone production in Lepidoptera. A radioenzymatic assay coupled with high performance liquid chromatography revealed the presence of OA in the innervated sex-pheromone gland of the corn earworm moth Helicoverpa (Heliothis) zea. Significantly more OA was found in glands just before the onset of scotophase (ca 320 fmol/gland), compared to levels at mid-photophase or just after the onset of scotophase (ca 160 fmol/gland).

Exogenous OA had several actions on pheromone production. H. zea virgin females normally do not produce pheromone during the photophase, but highly significant levels of pheromone were induced by injection of OA into intact, day-2 photophase females. Importantly, this effect was absent in older females that showed increased levels of flight and oviposition activity. A second action of OA was revealed in isolated abdomen preparations from day-2 H. virescens females. Exogenous OA stimulated highly significant increases in pheromone production if abdomens were treated at the onset of scotophase, but not if they were treated in photophase. This critical period for OA action in these reduced preparations coincided with the time when peak levels of OA were present in the pheromone gland tissue. OA is therefore sufficient to induce pheromone production, but its actions in these short-lived insects depend on factor such as age and photoperiod. Diel fluctuations in OA levels in the pheromone gland, together with the observed phermonotropic actions of this amine, support the hypothesis that OA is involved in the regulation of pheromone production in these insects.     

The circadian rhythm of the sex-pheromone-mediated behavioral response in the turnip moth, Agrotis segetum, is not controlled at the peripheral level

The pheromone-mediated upwind flight of male turnip moths was observed in a flight tunnel at different times of day under conditions of a light-dark (LD) cycle, constant darkness (DD), and a shifted photoperiod. Under both LD and DD conditions, a significantly larger number of males flew to the pheromone during both the scotophase and the subjective scotophase than during the photophase and the subjective photophase for 2 consecutive days. When 1-day-old moths were transferred to a shifted LD cycle with lights turned off 4 h earlier, male behavioral responses to the pheromone advanced in time accordingly by 4 h. This showed that male behavioral responses to the pheromone are under the control of an endogenous oscillator. To further examine the level at which the circadian rhythm of the male behavioral response is regulated, the authors tested the olfactory responses of male antennal receptors to pheromone stimuli by means of electroantennograms (EAG) at different times of day. No significant variation in the sensitivity of the male antennal response to the pheromone was observed in terms of time of day. The results suggest that circadian regulation of the rhythmic behavioral response to pheromones in the male Agrotis occurs at the central nervous system level.     

烟夜蛾雄蛾性附腺因子对雌蛾性信 息素合成的抑制作用

烟夜蛾Helicoverpa assulta处女蛾在交配后1 h,其性信息素滴度即显著降低,72 h内未见恢复。生测结果表明,烟夜蛾性信息素合成抑制因子主要来源于雄蛾性附腺。不同日龄雄蛾性附腺提取物的抑制活性无显著差异。光暗期对其活性具显著影响,暗期中雄蛾的性附腺物质对雌蛾性信息素合成具有较强抑制作用,而光期中雄蛾的性附腺物质不具抑制活性。在暗期的不同时间处理,对处女蛾性信息素合成的抑制作用无显著差异。雄蛾性附腺提取物对雌蛾性信息素合成的抑制作用与注射剂量有明显的相关性,0.2 ME（雄蛾当量）是产生显著抑制作用的最小剂量。对交配雌蛾注射性信息素生物合成激活神经肽（PBAN）提取物后,其性信息素合成又可恢复,这说明雌蛾交配后,性信息素滴度降低的原因是由于缺少了PBAN的调控。     

Mechanisms of premating isolation between Helicoverpa armigera (Hübner) and Helicoverpa assulta (Guenée) (Lepidoptera: Noctuidae)

Helicoverpa armigera and Helicoverpa assulta are sympatric sibling species, and in the laboratory they can interbreed and produce viable offspring. To assess the contributions of temporal barriers and sexual barriers to premating isolation, we investigated both the temporal rhythms of calling behavior and pheromone titers of H. armigera and H. assulta females and the behavioral responses of males to conspecific and heterospecific calling females in a wind tunnel. Both H. armigera and H. assulta females called throughout the scotophase, and there was more calling during the second half of the scotophase than during the first half. Maximal pheromone titer and maximal calling activity in H. armigera synchronously occurred at the sixth hour into the scotophase, whereas, in H. assulta, the maximal pheromone titer occurred 2 h before the peak of calling. Pheromone blend ratios of the two species were opposite and, within each species, changes in the ratio within the scotophase and at different ages were relatively small. Males of both H. armigera and H. assulta responded strongly to their conspecific calling females in the wind tunnel and completed the whole courtship sequence. In contrast, they did not land and had no copulation attempts in response to heterospecific calling females. These results show that the two species do not have obvious temporal differences in calling behavior and pheromone production, and the specificity of sex pheromone blend emitted by females plays a key role in their premating isolation. In addition, we summarized the potential isolation mechanisms of H. armigera and H. assulta.     

豆野螟成虫行为学特征及性信息素产生与释放节律

豆野螟Maruca vitrata (Fabricius)是一种严重的泛热带豆类蔬菜害虫。本文在（29±1）℃、相对湿度75%～80%、光周期14L∶10D条件下研究了豆野螟成虫的羽化、交尾行为以及雌蛾性信息素的释放节律。结果表明：其羽化行为全天可见,在雌蛾中,86%于暗期羽化; 在雄蛾中,73%于暗期羽化。雌雄蛾羽化行为在暗期第4、5和8 h差异达到显著 (t>4; P<0.05)。交尾活动发生在暗期19：00到5：00之间,交尾持续时间最短约为20 min,最长约为90 min,3日龄进入暗期第5 h具有最高的交尾率。1、6和7日龄成虫具有单个交尾高峰,2到5日龄成虫具有两个交尾高峰。同一日龄成虫交尾在暗期前半段平均花费的时间要明显高于在后半段花费的时间。低龄和高龄的成虫用于交尾的时间明显高于中龄的性成熟成虫。成虫的开始交尾时间随着日龄的增加逐渐前移。雄蛾对进入暗期后第5 h和第9 h处女雌蛾的性腺提取物和空气收集性信息素的触角电位反应最强,对 3日龄处女雌蛾的性腺提取物和空气收集性信息素的触角电位反应最强。处女雌蛾田间诱蛾试验表明：23：00-01：00为诱蛾高峰期,3日龄处女雌蛾的诱蛾效果最好。该蛾的羽化、交尾及性信息素产生与释放均存在节律上的一致性。雌蛾的性信息素释放的时间较长,见于整个暗期,然而交尾行为发生时间较短,主要发生于两个交尾高峰之间。     

Sublethal effects of chlordimeform on chemical communication and other reproductive behaviors in the female cabbage looper moth (Lepidoptera: Noctuidae)

Insecticides can affect the complex coordination of activities associated with reproduction through their sublethal impact on the nervous system. Our objective was to document the effects of a sublethal dose (1% mortality) of chlordimeform on reproductive events in the female cabbage looper moth, Trichoplusia ni. A significantly higher percentage of females treated with chlordimeform initiated calling at some time during the scotophase. Chlordimeform stimulated pheromone emission early in the scotophase. However, late in the scotophase pheromone emission was significantly lower in chlordimeform-treated females when compared with control females. Overall, a lower amount of pheromone was detected in glands of chlordimeform-treated females. This effect was significant only during the second half of the scotophase. We suggest that chlordimeform stimulates pheromone transport to the gland surface and calling behavior resulting in depletion of pheromone reserves over the course of the scotophase. Chlordimeform also decreased the mating success of males. Oviposition and egg hatch were also affected by chlordimeform. Mated females treated with chlordimeform laid significantly fewer eggs than acetone-treated females. In addition, hatchability of eggs laid by mated female T. ni treated with chlordimeform was significantly lower than for eggs laid by control females.     

大螟成虫性信息素生物合成和释放及求偶和交配行为的昼夜节律

【目的】探索大螟Sesamia inferens性信息素顺11-十六碳烯乙酸酯(Z11-16∶Ac)和顺11-十六碳烯醇(Z11-16∶OH)的合成和释放及求偶和交配行为的昼夜节律,及其与田间性信息素诱捕的关系。【方法】通过溶剂浸提和固相微萃取(solid phase microextraction, SPME)分析大螟雌蛾性信息素Z11-16∶Ac和Z11--16∶OH的滴度,结合行为观测和多地田间实时性信息素诱捕数据,调查大螟性信息素的生物合成、释放及求偶和交配行为的昼夜节律。【结果】大螟雌蛾腺体内性信息素Z11-16∶Ac和Z11-16∶OH含量可检测到的时间始于暗期前1 h,暗期后4 h快速增加,暗期8 h为第1次高峰,但光期1h又一次高峰,光期5 h还可以被显著检测到。分泌至腺体外的性信息素化合物可检测到的时间始于暗期后6 h,高峰期在暗期后10 h,光期后1 h性信息素Z11-16∶Ac滴度达到96.9±20.9 ng/雌。采用溶剂浸提法获得的Z11-16∶Ac和Z11-16∶OH的比例在暗期平均为2.8±1.9,在光期平均为2.5±0.9,统计上二者没有显著差异,而SPME法获得的Z11-16∶Ac和Z11-16∶OH的比例在暗期平均为8.5±1.2,在光期平均为5.7±0.6,统计上二者差异显著。产卵器伸出时间发生在暗期6-8 h,产卵器伸出持续时间平均为80.8±4.4 min。大螟的交配发生在暗期4-10 h,交配持续时间平均为83.4±5.0 min。广东、四川、浙江、江苏四省性诱自动计数的田间每日每小时实时计数数据显示,越冬代诱蛾比较集中,之后的世代则比较分散,田间雄蛾的性诱昼夜节律受地理环境、季节和世代等因子的影响。【结论】本研究发现大螟交配和性信息素释放的昼夜节律在时间上不一致,交配时间在暗期较早时段。雌蛾性信息素有效的释放时间范围比雄蛾对性信息素反应的要小。产卵器伸展与雌蛾性信息素化合物的释放速率加快和扩散 范围有关。     

Female sex pheromone suppression and the fate of sex-peptide-like peptides in mated moths of Helicoverpa armigera

Insect males produce accessory gland (MAG) factors that are transferred in the seminal fluid to females during copulation, and elicit changes in the mated female's behavior and physiology. Our previous studies showed that the injection of synthetic Drosophila melanogaster sex-peptide (DrmSP) into virgin females of the moth Helicoverpa armigera causes a significant inhibition of pheromone production. In this and other moth species, pheromone production, correlated with female receptivity, is under neuroendocrine control due to the circadian release of the neuropeptide PBAN. In this study, we show that PBAN, present in the hemolymph during the scotophase in females, is drastically reduced after mating. We also identify 4 DrmSP-like HPLC peaks (Peaks A, S1, S2, and B) in MAGs, with increasing levels of DrmSP immunoreactivity during the scotophase, when compared to their levels observed during the photophase. In H. armigera MAGs, a significant reduction in the pheromonostatic peak (Peak B) was already evident after 15 min of copulation, and depletion of an additional peak (Peak S2) was evident after complete mating. Peak A is also detected in female brains, increasing significantly 1 h after mating, at which time inhibition of pheromone biosynthesis also occurs. However, changes corresponding to the other MAG peaks were not detected in mated female tissues.     

The interrelationships between serotonin production and locomotion in different light regimes in southwestern Michigan opilionids, Leiobunum longipes

The comparison was made of the effect of LL and DD with LD 14:10 photoperiods on the 24-h secretion cycle of serotonin secretion and the activity patterns of Leiobunum longipes from Southwestern Michigan. LL and DD altered the normal activity patterns but did not change the pattern of serotonin secretion. The activity pattern in normal photoperiod (LD 14:10) produced a 12-h cosinor pattern, resulting in a 24-h biphasic activity peak model. The activity peaked in both scotophase and photophase . The altered patterns in LL and DD were different. In LL a rhythmic component could not be statistically determined. A high, irregular level of activity was seen, higher than the mean level in LD. In DD a combined 24 and 48 h cosinor pattern best fit the observed data. The major peaks occurred in nature during every other photophase and alternate scotophase time in the constant photoperiod conditions. Serotonin secretion patterns in LD, LL, and DD statistically fitted a 24-h cosinor model. Peak secretion times occurred in mid photophase for LD and LL. A later photophase peak was seen in DD. LL animals showed a mean level of serotonin and secretion pattern which was not statistically different from LD. The hypothesis that LD photoperiods direct a peak of serotonin secretion which initiated the activity pattern could not be accepted.     

Effects of octopamine and forskolin on excitatory junction potentials of developing and adult moth muscle

Intracellular recordings were made from the dorsal longitudinal muscle of Manduca sexta to determine the effects of development and octopamine on the excitatory junction potential (EJP) produced in response to electrical stimulation of the motor nerve. Observations were made on pharate moths during the last 3 days before eclosion and on adults. In saline, the highest values for EJP amplitude and maximum rate of rise and for resting membrane potential are reached on the nineteenth day of the pupal period, the day the animal ecloses; adult values are slightly lower. In animals of all ages tested, DL-octopamine (5 X 10(-6) M) increases EJP amplitude and maximum rate of rise. Increases in amplitude are greater in animals at stage day 17 and 18 than in animals at stage day 19 and adult. Octopamine has no effect on EJP rise time (onset to peak) or recovery time (peak of EJP to 70% recovery). Octopamine causes a hyperpolarization of about 6 mV. The results show that developmental changes in synapse properties are paralleled only in part by changes induced by octopamine. Both development and octopamine increase EJP amplitude and maximum rate of rise, and neither alter rise time. EJP recovery time changes with development but not in response to octopamine. Forskolin (10(-4) M) mimics the effects of octopamine on day 17 animals. EJP amplitude and maximum rate of rise are increased by forskolin, and rise time and recovery time are unaffected. Forskolin, like octopamine, causes a 6 mV hyperpolarization of the muscle fiber. These results suggest that octopaminergic modulation at the Manduca sexta dorsal longitudinal neuromuscular junction may be mediated by changes in intracellular levels of cyclic AMP.