Journal club: Recent Clione papers

Arshavsky published a series of studies on the Clione swim CPG. Those papers are "must read" for researchers who work on CPG. I pay the highest respect to them.They were published in late 80's and now can be categorized as classical papers.
   More recently, there came a series of papers performing more detailed(?) analyses on this system. The following are my impressions with regard to those recent Clione papers.

2004
"Cellular mechanisms underlying swim acceleration in the pteropod mollusk Clione limacina"
by Pirtle and Satterlie
Integr. Comp. Biol. (2004) 44 (1): 37-46. doi: 10.1093/icb/44.1.37

Clione can swim faster when attacking a prey. It had been suggested that 5-HT mediates the acceleration of the swim motor pattern. In this study, the authors examined what membrane current components were modified by 5-HT.
   It seems to me that the experiments were not well designed. The way they compared the effects of drugs seems problematic (e.g., Fig. 7D). Figures were not well arranged. A control swim activity was not presented in Fig. 2 but then shown in Fig. 3. The authors called ion channel blockers as "antagonists." Antagonists are for receptors. No description of what neurons they used. The introduction was great, though.


2006
"The contribution of the pleural type 12 interneuron to swim acceleration in Clione limacina"
by Pirtle and Satterlie
Invert Neurosci (2006) 6:161–168. DOI 10.1007/s10158-006-0029-8

In this paper, the authors examined the role of type-12 neurons in the swim acceleration.
   Type-12 neuron is recruited into the type7/8 half-center network when the CPG gets into the fast swim mode. Arshavsky et al. (1985) suggested that this neuron plays an important role in the swim acceleration by rewiring the circuit. It turned out that activation of type-12 had only a transient effect on the swim cycle frequency. They suggested that type 12 has rather minor roles in maintaining the fast swim mode. Its function may be bilateral coordination or to increase the stability of the network. Despite negative results, this paper is more interesting than the other two.


2010
"A hyperpolarization-activated inward current alters swim frequency of the pteropod mollusk Clione limacina"
Pirtle, Willingham, and Satterlie
Comparative Biochemistry and Physiology, Part A 157 (2010) 319–327. DOI:10.1016/j.cbpa.2010.07.025

I don't see much difference between this and the previous 2004 paper. The only change was that they now show ZD7288 data instead of CsCl. In Fig. 5E. They stated ZD7288 blocked the 5-HT effect. I cannot agree with that. If compared with Fig. 4D data, I see that 5-HT still increases the swim cycle frequency even in the presence of ZD7288. Oh and again they were still calling ZD7288 as an "antagonist" for Ih current.