LAY ABSTRACT IBN-9807914 Cellular mechanisms of Activation and Control of Complex Behavior by Peptidergic Neuron Peptidergic neuroendocrine neurons are activated when an animal makes prolonged contact with a mass of eggs laid by other individuals. Activation of these neurons in the central nervous system, in turn, results in a sequence of behaviors in the same individual, including egg laying, mating as a female during egg laying, and mating as a male after egg laying. This process in which a sign stimulus (possibly a chemical stimulus in the egg mass) leads to a sequence of behaviors has parallels to genetically determined, instinctive behavior associated with reproduction in other animals. This preparation is advantageous for detailed investigation since activity of the peptidergic neurons can be monitored in both reduced experimental preparations and intact animals, and their effects on neuronal circuits and relationships to behavioral control can be investigated at the cellular and molecular levels in considerable detail. One goal is to describe in detail how neurotransmitters released from the peptidergic neurons affect neuronal circuits controlling locomotion and feeding during the behaviors. As in other animals, there appears to be an internal drive for reproductive behavior, in which the threshold for induction of egg laying by the releasing stimulus in the egg mass changes according to the reproductive cycle. An idea we wish to test further is that the physiological properties of the peptidergic neurons and cells that excite them constitute the neural mechanism for the internal drive. The research should result in a clearer understanding of the contributions of peptidergic neural systems to neural regulation of complex, genetically determined behaviors. The principles of organization and control by this neural system may be useful for understanding fundamental mechanisms that underlie complex behavior in higher forms.
