Further studies on peripeduncular-hypothalamic pathways involved in sexual behavior in the female rat

Abstract

A series of preliminary experiments demonstrated that injection of 22 m M sodium pentobarbital in the brain of the rat blocked synaptic transmission at the site of injection; the same concentration of pentobarbital did not block fiber conduction. Based on the latter information, 22 m M pentobarbital was applied to different parts of the peripeduncular-hypothalamic pathways resonsible for the conduction and generation of potentials evoked in the ventromedial nucleus (VMN) by stimuli applied to the peripeduncular nucleus (PPN), to determine whether participation of the amygdala and bed nucleus of the stria terminalis involves the transynaptic activation of neuron somas at these places or the operation of passing fibers only. We determined that potentials evoked in the VMN by PPN stimulation involves synaptic activity in both the lateral amygdaloid nucleus and the bed nucleus of the stria terminalis. Both structures receive PPN-originated activity independently, and both structures contribute to the generation of PPN-VMN evoked responses, presumably through temporal or spatial summation of inputs in the VMN. We also showed that activity in the lateral amygdaloid nucleus is conducted toward the VMN along fibers in the stria terminalis. We propose that the synaptic interactions thus demonstrated serve as integrating relays for different sensory modalities and hormone actions regulating sexual behavior.