Male sensitivity to pheromone

Our agonist studies were designed to further document the effect of lower doses of OA on male sensitivity to pheromone (as shown in Figure 1), and to provide a pharmacological profile that could be compared with data from other published studies on OA receptors (12-14). The compounds included 1) the phenylethylamines synephrine and dopamine, 2) the formamidine chlordimeform, and 3) the substituted imidazolines naphazoline (2-[ 1-naphthylmethyl] imidazoline ), lofexidine (2-[ l-(2,6-dichlorophenoxy)ethyl]-2-imidazoline), XAMI (2,3-xylylaminomethyl-2-imidazoline), clonidine (2-(2,6-dichloro-anilino)-2-imidazoline), tolazoline (2-benzyl-2-imidazoline), and tramazoline (2-[5,6,7,8-tetrahydro-1-naphthyl]amino-2-imidazoline) ... 

Figure 2. Percentage of male CL making source contact (0.01 mg pheromone) 4-5 hours after injection of OA and agonist compounds ( ig/g) The curves for each compound represent the range of doses over which an effect was observed only on male sensitivity to pheromone, without a significant effect on male flight performance. N - 80 for each dose. The solid line indicates control response level (16%).

One of the proposed mechanisms by which OA exerts its regulatory actions is via an adenylate cyclase (12-18). In a preliminary test male CL were treated with the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX), alone and with OA. The dose of OA (10 ug/g) was one that induced little or no effect on male sensitivity (see Figure 1). Results showed that when treated with IBMX alone (10 Ug/g) male response to a low dosage of pheromone (0.01 mg) was not significantly enhanced over that observed with controls, or OA alone (20 vs. 15% source contacts respectively). However, when treated with 10 Ug/g OA and 10 Ug/g IBMX, 78% of the males successfully reached the source. IBMX clearly potentiated the effect of a low dose of OA on male sensitivity to pheromone ... 

We first determined the ability of selected agonist compounds to mimic the effect of OA on male sensitivity to the pheromone by treating males with a dose series of each compound and then testing them with the 0.01 mg dosage of pheromone, which under control conditions elicits a low level of response (Figure 2). It is important to note... 

In the second series of tests the ability of several of the antagonists to block the effect of OA on male sensitivity was assessed. Data in Figure 5 show that mianserin, chlorpromazine, and yohimbine reversed the effect of OA on male sensitivity to the 1 mg dosage of pheromone, with chlorpromazine and yohimbine exhibiting greater potency than when presented alone (Figure 4). 

Males are extremely sensitive to pheromones given off by females... 

This distinction clarifies the surprising differential sensitivity of male and female 7. paraconfusus to components of their pheromone and to that of I. pint. Males and females are equally sensitive to their natural pheromone and to its component, (+ )ipsdienol, over a wide range of concentrations. However, females are significantly more sensitive to pheromonal ( + )ipsdienol than to allomonal (-)ipsdienol (the pheromone of I. pini), whereas males are more sensitive to allomonal (- )ipsdienol than to their own pheromonal (+ )ipsdienol (Light and Birch, 1982). There is a clear adaptive advantage for males to locate new host material quickly and to avoid resources occupied by /. pini, unless nothing else is available, since if the two species do co-colonize a resource, the reproductive potentials of both are reduced. This premium on selection of unoccupied resources underlies the high sensitivity of males to allomonal ipsdienol. The interruption of response in 7. paraconfusus by verbenone from D. brevicomis may have a similar basis. 

The production of a female-influencing secretion from the chin gland of male Plethodontid salamander (P. jordani) points to a similar extension of function by the acquisition of female olfactory sensitivity to an intercellular signal protein. Female receptivity is enhanced by a male cytokine-like compound of the interleukin-6 family, in its released form. Rollman et al. (1999) note that pheromonal activity is a previously unrecognised function for cytokines. 

Earlier experiments based on EAG and SSR highlighted the inordinate specificity and sensitivity of the insect olfactory system. While minimal structural modifications to pheromone molecules render them inactive [12], a single molecule of the native ligand is estimated to be sufficient to activate an olfactory neuron in male antennae [14]. The large number of detectors certainly contributes to the sensitivity of the olfactory system, but selectivity is a matter of... 

The male-produced aggregation pheromone of the square-necked grain beetle, Cathartus quadricollis has been identified to be (3R,6 )-3-acetoxy-7-methylnon-6-ene 157 [297]. The compound, termed quadrilure, is attractive to both sexes, however, females are more sensitive at low concentrations. The (S)-enantiomer is biologically inactive. 

Another unusual structure was identified from cereal leaf beetles, Oulema melanopus ( )-8-hydroxy-6-methyl-6-octen-3-one 199 was found to be a male-specific volatile. Electrophysiological investigations showed a sensitive detection of 199 by both sexes which is consistent with a male-produced aggregation pheromone [367]. The behaviour mediating capacity of the compound needs to be proven. 

The olfactory system of the male is extremely sensitive to 17,20jSP. The fish respond to a concentration of 5 x 10 ° mol/1. This amount(3 x 10 molecules) is released by a 90 mm female fish into 1 liter water. The females are also very sensitive to 17,20/3P. It may stimulate ovulation. Of 47 vitellogenic females 13 ovulated when 17,20/3P was added to the water, while only 1 of 43 did so in untreated water (Dulka etal, 1987). Both sexes probably release 17,20/3P. Ecologically, this bisexual pheromone is thought to synchronize milt production with ovulation and thus coordinate spawning in local populations (Dulka etal, 1987 Sorensen and Stacey, 1990). 

Sorensen, P. W., Stacey, N. E., and Kara, T. J. (1990b). Acute olfactory sensitivity and specificity of mature male goldfish to water borne androgenic steroids a class of inhibitory pheromones. Chemical Senses 15,644. 

Female gypsy moths emit the pheromone disparlure (top) to entice male gypsy moths (bottom left) into mating. The males ate so sensitive to this compound that they can detect one molecule in 1017 molecules of air. This astounding sensitivity enables them to respond to a female who may be more than 1 kilometer away. However, they can also be tricked into responding to insecticide traps laced with synthetic disparlure (bottom right). 

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