I'm an undergraduate student at the UA, majoring in molecular and cellular biology. I'm working in the neurobiology laboratory of Dr. Alan Nighorn, under the direction of postdoctoral research associate Dr. Andrew Dacks, through the Undergraduate Biology Research Program. Using the moth, Manduca sexta, I am looking for the sequence of the gene encoding in a serotonin receptor of the 5-HT7 family.

Serotonin is a neurotransmitter in a wide-range of animals, across both vertebrate (including human) and invertebrate phyla. We are looking at it in the Manduca olfactory system, which is very similar to the human olfactory system.

In the olfactory pathway, first odorant molecules bind to sensory neurons, which are located on the antenna in the moth, and in the nasal cavity of humans. The odorant information from many sensory neurons is then passed, through the olfactory nerve, to the antennal lobe or olfactory bulb, in moth and human, respectively. At these "relay stations," odorant information is likely processed and sorted, and then sent to higher order processing regions of the brain.

Serotonin plays important modulatory roles at the antennal lobe (AL) of the moth. At high concentration, by reducing potassium currents (Mercer et al., 1995), serotonin enhances the excitatory response of AL neurons (Kloppenburg and Hildebrand, 1995); at low concentration, serotonin reduces the excitatory response (Kloppenburg and Hildebrand, 1995). Serotonin also seems to contribute to the circadian rhythm of the moth, as in the ALs, at night when the animal is most active, serotonin level is highest resulting in AL neurons being most responsive (Kloppenburg et al., 1999).

To better understand the effects and roles of serotonin as a neurotransmitter, we need to understand its receptors. Many receptors exist for serotonin (5-hydroxytryptamine, or 5-HT). In mammals, seven distinct families of 5-HT receptors have been identified (Barnes and Sharp, 1999). Since the divergence of these seven families of receptors is estimated to be before the divergence of vertebrates from invertebrates (Tierney, 2001), homologues of the mammalian receptors should exist in invertebrates as well. Thus, we predict the existence of a serotonin receptor in the moth that is homologous to the mammalian 5-HT7 receptor. So far, two 5-HT receptors, both of the 5-HT1 family, have been cloned from Manduca sexta (Dacks et al., 2006), and we're trying to clone one of the 5-HT7 family. If we are successful at cloning, we will determine the expression pattern of the receptor, as well as characterize it.

Serotonin is an important molecule in many animals, including human, and it plays modulatory roles in the AL of Manduca sexta. The study of serotonin receptors is essential toward understanding the underlying mechanisms that produce the effects of serotonin.
References:
1. Barnes NM, Sharp T. A review of central 5-HT receptors and their function. Neuropharmacology. 1999; 38:1083-1152.
2. Dacks AM, Dacks JB, Christensen TA, Nighorn AJ. The cloning of one putative octopamine receptor and two putative serotonin receptors from the tobacco hawkmoth, Manduca sexta. Insect Biochem Mol Biol. 2006; 36:741-747.
3. Kloppenburg P, Ferns D, Mercer A. Serotonin enhances central olfactory neuron responses to female sex pheromone in the male sphinx moth Manduca sexta. J Neurosci. 1999;19 (19):8172-8181.
4. Kloppenburg P, Hildebrand JG. Neuromodulation by 5-hydroxytryptamine in the antennal lobe of the sphinx moth Manduca sexta. J Exp Biol. 1995; 198:603-611.
5. Mercer A, Hayashi J, Hildebrand JG. Modulatory effects of 5-hydroxytryptamine on voltage-activated currents in cultured antennal lobe neurons of the sphinx moth Manduca sexta. J Exp Biol. 1995;198:613-627.
6. Tierney AJ. Structure and function of invertebrate 5-HT receptors: a review. Comp Biochem Physiol. 2001; 128:791-804.

Wujie Zhang, UBRPer in Dr. Alan Nighorn's lab, ARL-Neurobiology