The motor output of hindlimb innervating segments of the spinal cord is modulated by cholinergic activation of rostrally projecting sacral relay neurons.

Cholinergic networks have been shown to be involved in generation and modulation of the locomotor rhythmic pattern produced by the mammalian central pattern generators. Here, we show that changes in the endogenous levels of acetylcholine in the sacral segments of the isolated spinal cord of the neonatal rat modulate the locomotor-related output produced by stimulation of sacrocaudal afferents in muscarinic receptor-dependent mechanisms. Cholinergic components we found on sacral relay neurons with lumbar projections through the ventral and lateral funiculi are suggested to mediate this ascending cholinergic modulation. Our findings, possible mechanisms accounting for them, and their potential implications are discussed.

Neuroanatomical basis for cholinergic modulation of locomotor networks by sacral relay neurons with ascending lumbar projections.

Synaptic excitation by sacrocaudal afferent (SCA) input of sacral relay neurons projecting rostrally through the ventral white matter funiculi (VF neurons) is a potent activator of the hindlimb central pattern generators (CPGs) in rodent spinal cords lacking descending supraspinal control. Using electrophysiological recordings from the sacral and lumbar spinal segments, we show that the motor output of the lumbar segments produced by SCA stimulation is enhanced by exposing the sacral segments of the neonatal rat spinal cord to the acetylcholinesterase inhibitor edrophonium (EDR). Histochemical and immunostaining of the sacral cord reveals expression of acetylcholinesterase activity, ability to synthesize acetylcholine, and/or innervation by cholinergic synaptic inputs in significant proportions of fluorescently back-labeled sacral VF neurons. Moreover, the majority of the VF neurons express M2 muscarinic receptors, raising the possibility that the elevated acetylcholine levels resulting from inhibition of acetylcholinesterase act on such receptors. Indeed, sacral application of atropine or the M2 -type receptor antagonist methoctramine was found to reverse the effects of EDR. We suggest that variations in the sacral level of acetylcholine modulate the SCA-induced locomotor rhythm via muscarinic receptor-dependent mechanisms and that the modified activity of sacral VF neurons in the presence of an acetylcholinesterase inhibitor can be partially ascribed to the cholinergic components associated with them. Thus, pharmacological manipulations of the sacral cholinergic system may be used to modulate the locomotor-related motor output in the absence of descending supraspinal control.

Characterization of sacral interneurons that mediate activation of locomotor pattern generators by sacrocaudal afferent input.

Identification of the neural pathways involved in retraining the spinal central pattern generators (CPGs) by afferent input in the absence of descending supraspinal control is feasible in isolated rodent spinal cords where the locomotor CPGs are potently activated by sacrocaudal afferent (SCA) input. Here we study the involvement of sacral neurons projecting rostrally through the ventral funiculi (VF) in activation of the CPGs by sensory stimulation. Fluorescent labeling and immunostaining showed that VF neurons are innervated by primary afferents immunoreactive for vesicular glutamate transporters 1 and 2 and by intraspinal neurons. Calcium imaging revealed that 55% of the VF neurons were activated by SCA stimulation. The activity of VF neurons and the sacral and lumbar CPGs was abolished when non-NMDA receptors in the sacral segments were blocked by the antagonist CNQX. When sacral NMDA receptors were blocked by APV, the sacral CPGs were suppressed, VF neurons with nonrhythmic activity were recruited and a moderate-drive locomotor rhythm developed during SCA stimulation. In contrast, when the sacral CPGs were activated by SCA stimulation, rhythmic and nonrhythmic VF neurons were recruited and the locomotor rhythm was most powerful. The activity of 73 and 27% of the rhythmic VF neurons was in-phase with the ipsilateral and contralateral motor output, respectively. Collectively, our studies indicate that sacral VF neurons serve as a major link between SCA and the hindlimb CPGs and that the ability of SCA to induce stepping can be enhanced by the sacral CPGs. The nature of the ascending drive to lumbar CPGs, the identity of subpopulations of VF neurons, and their potential role in activating the locomotor rhythm are discussed.

Human CTL epitopes prostatic acid phosphatase-3 and six-transmembrane epithelial antigen of prostate-3 as candidates for prostate cancer immunotherapy.

Specific immunotherapy of prostate cancer may be an alternative or be complementary to other approaches for treatment of recurrent or metastasized disease. This study aims at identifying and characterizing prostate cancer-associated peptides capable of eliciting specific CTL responses in vivo. Evaluation of peptide-induced CTL activity in vitro was done following immunization of HLA-A2 transgenic (HHD) mice. An in vivo tumor rejection was tested by adoptive transfer of HHD immune lymphocytes to nude mice bearing human tumors. To confirm the existence of peptide-specific CTL precursors in human, lymphocytes from healthy and prostate cancer individuals were stimulated in vitro in the presence of these peptides and CTL activities were assayed. Two novel immunogenic peptides derived from overexpressed prostate antigens, prostatic acid phosphatase (PAP) and six-transmembrane epithelial antigen of prostate (STEAP), were identified; these peptides were designated PAP-3 and STEAP-3. Peptide-specific CTLs lysed HLA-A2.1+ LNCaP cells and inhibited tumor growth on adoptive immunotherapy. Furthermore, peptide-primed human lymphocytes derived from healthy and prostate cancer individuals lysed peptide-pulsed T2 cells and HLA-A2.1+ LNCaP cells. Based on the results presented herein, PAP-3 and STEAP-3 are naturally processed CTL epitopes possessing anti-prostate cancer reactivity in vivo and therefore may constitute vaccine candidates to be investigated in clinical trials.