No abstract

Biogenic amines modulate key behaviors in both vertebrates and invertebrates. In Caenorhabditis elegans, tyramine (TA) and octopamine (OA) inhibit aversive responses to 100%, but not dilute (30%) octanol. TA and OA also abolish food-and serotonin-dependent increases in responses to dilute octanol in wild-type but not tyra-3(ok325) and f14d12.6(ok371) null animals, respectively, suggesting that TA and OA modulated responses to dilute octanol are mediated by separate, previously uncharacterized, G-protein-coupled receptors. TA and OA are high-affinity ligands for TYRA-3 and F14D12.6, respectively, based on their pharmacological characterization after heterologous expression. f14d12.6::gfp is expressed in the ASHs, the neurons responsible for sensitivity to dilute octanol, and the sra-6-dependent expression of F14D12.6 in the ASHs is sufficient to rescue OA sensitivity in f14d12.6(ok371) null animals. In contrast, tyra-3::gfp appears not to be expressed in the ASHs, but instead in other neurons, including the dopaminergic CEP/ADEs. However, although dopamine (DA) also inhibits 5-HT-dependent responses to dilute octanol, TA still inhibits in dop-2; dop-1; dop-3 animals that do not respond to DA and cat-2(tm346) and Pdat-1::ICE animals that lack significant dopaminergic signaling, suggesting that DA is not an intermediate in TA inhibition. Finally, responses to TA and OA selectively desensitize after preexposure to the amines. Our data suggest that although tyraminergic and octopaminergic signaling yield identical phenotypes in these olfactory assays, they act independently through distinct receptors to modulate the ASH-mediated locomotory circuit and that C. elegans is a useful model to study the aminergic modulation of sensory-mediated locomotory behaviors.

Depcarfrnurzf of Biology, Mcil4usfer fiiversify, Hamilfort, Onr. HARRIS, G. P. 1980. Temporal and spatial scales in phytoplankton eco1ogy. Mechanisms, methods, models, and management. Can. 3. Fish. Aquat. Sci. 319: 879-900.This article is essentially a review of the temporal and spatial scales iaf variability in both marine and freshwater planktonic environnlents and the algal responses to those scales. I assert that therc are problerns with our present understanding of thew scales and the use of imapprapriate assumptions concerming the occurrence of steady-state conditions. In a nonsteady-state environment the concepts of limiting nutrients must be changed, and the extrapolation from culture to field conditions is fraught with problems. In this paper I revlew the evidence for the existence and importance of small-scale, high frequency and large-scale, Ic~w frequency variation in the planktonic environment and show that mach variation fu~~darnentalIy affects our understanding of existing processes. Methodology and models nalust also reflect the true scales of variability which exist. I show that there are, at present, problems with our understanding of planktonic processes which greatly atfect our ability to manage water qaaality. New concepts and models are urgently needed. Finally I propose a ncw model of community structure and process in variable envircrn~nents which accoaants for the correct 'algal' scales of perturbation and response and allows certain predictions to be mads. I t is possible to reconcile certain problems and controversies i~, the literature by the use of such a model. An enhanced ahi1ity lo manage planktonic systerns should result from an improved understanding of the true scales of variability which exist. HARRIS, G. lB. 1980. Temporal and spatial scales in phytoplankton ecology. Mechanisms, naethods, n~odels, and management. Can. J. Fish. Aquat. Sci. 37: $77-900.Le prksent article est essentiellernent urie revue des echelles de variabilile temporelle et spatiale dans des environnements tant marins que d'eau douce et lies rkponses algaies 2 ces echelles. Je soaltiens que notre csmpr6hensiora actiielle de ccs Cchelles ek B'utilisation d'hypothises inapproprikes concernant l'occurrence de conditions dVCcluilibr-e laissent B dksirer. Dans un environraement nons en Cyuilibre, il fauiira modifier les notions d76I6ments nutritifs limitatifs, el l'extrapolation cle conditions d'Clevage B des coilditions sur le terrain est pleine de danger. Je passe ici en revue les preuvcs de I'existcnce et de B'importance d'une petite @cheile, d'une haute frkcjuence ct grande kchelle et er~fin d'une variation h faible frtquence de I'enviroianememt pla~~ctonique; je d h s n t r e de plus qti'rane telk variation affecte fc~ratiamentalcment notre cornpr6hension des processus actuels. La rnClhodologie et Ics rnodkles doivent arlssi seflCter les kclmelles de varlabilitc qui existent dans la rCalitC. Je dri-rnontrc l'existence cle problkmes aoklchant notre compr6hension des processus planctoniq~ies, influant granderrl...

Serotonin modulates behavioral plasticity in both vertebrates and invertebrates and in Caenorhabditis elegans regulates key behaviors, including locomotion, aversive learning and olfaction through at least four different 5-HT receptors. In the present study, we examined the serotonergic stimulation of aversive responses to dilute octanol in animals containing null alleles of these 5-HT receptors. Both ser-1 and mod-1 null animals failed to increase sensitivity to dilute octanol on food/5-HT, in contrast to wild-type, ser-4 or ser-7 null animals. 5-HT sensitivity was restored by the expression of MOD-1 and SER-1 in the AIB or potentially the AIY, and RIA interneurons of mod-1 and ser-1 null animals, respectively. Since none of these 5-HT receptors appear to be expressed in the ASH sensory neurons mediating octanol sensitivity, we identified a 5-HT6-like receptor, F16D3.7(SER-5), that was required for food/5-HT dependent increases in octanol sensitivity. ser-5 null animals failed to increase octanol sensitivity in the presence of food/5-HT and sensitivity could be restored by expression of SER-5 in the ASHs. Similarly, the RNAi knockdown of ser-5 expression in the ASHs of wild-type animals also abolished 5-HT dependent increases in octanol sensitivity, suggesting that SER-5 modulates the octanol responsiveness of the ASHs directly. Together, these results suggest that multiple amine receptors, functioning at different levels within the locomotory circuit, are each essential for the serotonergic modulation of ASH-mediated aversive responses.

Serotonin (5-HT) regulates key processes in both vertebrates and invertebrates. Previously, four 5-HT receptors that contributed to the 5-HT modulation of egg laying were identified in Caenorhabditis elegans. Therefore, to assess potential receptor interactions, we generated animals containing combinations of null alleles for each receptor, especially animals expressing only individual 5-HT receptors. 5-HTstimulated egg laying and egg retention correlated well with different combinations of predicted excitatory and inhibitory serotonergic inputs. For example, 5-HT did not stimulate egg laying in ser-1, ser-7, or ser-7 ser-1 null animals, and ser-7 ser-1 animals retained more eggs than wild-type animals. In contrast, 5-HT-stimulated egg laying in ser-4;mod-1 animals was greater than in wild-type animals, and ser-4;mod-1 animals retained fewer eggs than wild-type animals. Surprisingly, ser-4;mod-1;ser-7 ser-1 animals retained the same number of eggs as wild-type animals and exhibited significant 5-HT-stimulated egg laying that was dependent on a previously uncharacterized receptor, SER-5. 5-HT-stimulated egg laying was absent in ser-5;ser-4;mod-1;ser-7 ser-1 animals, and these animals retained more eggs than either wild-type or ser-4;mod-1;ser-7 ser-1 animals. The 5-HT sensitivity of egg laying could be restored by ser-5 muscle expression. Together, these results highlight the dual excitatory/inhibitory serotonergic inputs that combine to modulate egg laying.