Polyamines as olfactory stimuli in the goldfish Carassius auratus

Abstract

SUMMARY Electrophysiological responses of goldfish olfactory receptor neurons(ORNs) and goldfish behavioral responses to polyamines were investigated in vivo. Electro-olfactogram (EOG) recordings indicated that polyamines (putrescine, cadaverine and spermine) are potent olfactory stimuli for goldfish with estimated electrophysiological thresholds of 10–8–10–7 mol l–1,similar to that for L-arginine, the most stimulatory amino acid. Although thresholds were similar, the magnitude of the EOG responses to intermediate(10–5–10–4 mol l–1)and high (10–3 mol l–1) concentrations of polyamines dwarfed the responses to amino acids and related single amine containing compounds (amylamine and butylamine). The EOG responses to 0.1 mmol l–1 putrescine, cadaverine and spermine were, respectively,4.2×, 4.3× and 10.3× the response of the standard, 0.1 mmol l–1 L-arginine. Electrophysiological cross-adaptation experiments indicated that polyamine receptor sites are independent from those to L-amino acids (alanine, arginine, glutamate, lysine, methionine and ornithine), bile salts (sodium taurocholate and taurolithocholate), the single amine containing compounds (amylamine and butylamine) and ATP. Further, the cross-adaptation experiments revealed the existence of independent receptor sites for the different polyamines tested. Pharmacological experiments suggested that polyamine odorant transduction does not primarily involve the cyclic AMP and IP3 second messenger pathways. Behavioral assays indicated that polyamines are attractants that elicit feeding behavior similar to that elicited by L-amino acids.

High-affinity olfactory receptor for the death-associated odor cadaverine

“…Receptor affinities can be much lower in heterologous systems than in vivo (28)(29)(30), where expression of receptors and signaling components are presumably optimized. Nevertheless, the threshold of cadaverine detection by TAAR13c of 3 μM is very similar to in vivo thresholds observed for the intact olfactory system (6,31) and to thresholds measured for isolated olfactory sensory neurons (2). Although it is difficult to estimate naturally occurring cadaverine concentrations close to dead fish, the cadaverine concentration we measured in rotten zebrafish extracts was several orders of magnitude higher than the TAAR13c activation threshold, and presumably high enough to allow detection of that odor source from some distance.…”

“…This finding is consistent with electrophysiological studies indicating limited cross-adaptation of olfactory responses to cadaverine and putrescine (2). Here, we identified TAAR13c as a highly sensitive detector of odd-chained diamines that include the repulsive odor cadaverine.…”

“…It may be expected that animal species feeding on carcasses attribute a more positive valence to diamines, and indeed both putrescine and cadaverine have been reported to be feeding attractants for rats (1) as well as goldfish (2). Similarly, insects depositing their eggs in carcasses or other proteineacous materials are attracted by these diamines (3).…”

Smelling salt: Calcium as an odourant for fathead minnows

“…The current study is the first to demonstrate cross-adaptation between calcium and a second odourant. Cross-adaption has been seen in fish for other stimuli such as polyamines, bile salts and amino acids, but not calcium (Hansen et al, 2003;Michel et al, 2003;Rolen et al, 2003). A study by Hubbard et al (2002) showed that removal of calcium from the surrounding water for goldfish resulted in a small, but significant, increase in response to L-serine.…”

“…We hypothesized that this decrease in response may be due to cross-adaptation between calcium and L-arginine. Cross-adaptation occurs when two odourants have an overlap in the OSNs that recognize each odourant individually, such that when the OE is stimulated by one of the odourants, OSNs that would normally respond to the second odourant cannot respond to a second stimulus because they are already activated by the first odourant (Hansen et al, 2003;Michel et al, 2003;Rolen et al, 2003). Cross-adaptation, therefore, results in a reduced olfactory response to a second odourant after a first odourant has already activated OSNs required to perceive the second odourant.…”