Urotensin II in Invertebrates: From Structure to Function in Aplysia californica
(A) Representative examples. CBI-2 was stimulated throughout the protraction phase (open bar) to elicit single cycle motor programs; the inter-trial interval is 1 min. In control condition (A1), B8 is predominantly active during the retraction phase (filled bar), while B61 is only active during protraction. Perfusion of 10−6 M (A2) and 10−5 M (A3) apUII’ reduced the firing frequency of both B8 and B61, but had a lesser effect on the firing frequency of B4/5. Protraction is monitored via activity of I2, retraction via activity of BN2. (B) Group data showing the suppressive effects of 10−6 M and 10−5 M apUII’ on B8 firing frequency during protraction (B1), or during retraction (B2), and B61/62 firing frequency during protraction (B3). (C) Group data showing the lengthening of the latency to protraction initiation, measured as the time that elapsed from the onset of CBI-2 stimulation to the onset of I2 nerve activity (C1). apUII’ also reduced protraction duration (C2) and retraction duration (C3). *, p<0.05; **, p<0.01; ***, p<0.001; error bars represent SEM.