抄録
Animals flexibly adjust their endocrine, autonomic, and behavioral functions in response to ever-changing environments. Here the peptidergic nervous system is believed to play an important role. In this symposium, I introduce our recent studies on an extrahypothalamic GnRH (gonadotropin-releasing hormone) peptidergic neuron system, the terminal nerve (TN) GnRH system, which we suggest is neuromodulatory and is involved in the control of motivational state of the animal. By using a fish model system, the dwarf gourami (tropical freshwater fish) brain, we have demonstrated that TN GnRH neurons project widely in the brain, show characteristic pacemaker activities that are modifiable by multimodal sensory and hormonal inputs. The pacemaker activities are generated by the combination of a TTX-resistant persistent Na+ current and a certain kind of TEA-sensitive K+ current as well as the conventional TTX-sensitive Na+ current. The TN-GnRH neurons also express various kinds of voltage-dependent Ca2+ currents (mainly L, N, and R) and several different types of ionotropic as well as metabotropic glutamate receptors, which presumably play important roles in the physiological functions of the peptidergic modulator neurons. We find that solitary nest-building (NB) behavior of the male dwarf gourami in the absence of females can be quantitatively analyzed as a good index of motivated state. We obtained evidence to suggest the involvement of GnRH peptides in the control of this "motivated" NB behavior by analyzing effects of GnRH agonists and antagonists. [Jpn J Physiol 54 Suppl:S21 (2004)]
