Sundararaman N, Vertes RP, Perry GW (2004) Neurotoxic lesions of serotonin containing cells of the median raphe nucleus produce constant hippocampal theta rhythm in behaving rats. Neuroscience 2004 Abstracts 196.15. Society for Neuroscience, San Diego, CA.

Summary: The median raphe nucleus (MR) is a major serotonin containing cell group with pronounced projections to the forebrain. The MR exerts strong desynchronizing actions on the EEG activity of the hippocampus. MR stimulation desynchronizes the hippocampal EEG (or blocks theta), and electrolytic MR lesions produce continuous theta. Evidence suggests that desynchronizing actions of MR on the hippocampal EEG are mediated by serotonergic (5-HT) cells of MR. Injections of pharmacological agents into MR that suppress 5-HT MR activity generate theta at short latencies and for long durations. We examined the effects of the selective destruction of 5-HT cells of MR using the 5-HT neurotoxin, anti-SERT-SAP (Advanced Targeting Systems) on the EEG activity of the hippocampus in behaving rats. Under deep sodium pentobarbital anesthesia, rats were chronically prepared with bipolar electrodes, bilaterally in the dorsal hippocampus, a cortical screw for recording the cortical EEG and an indwelling cannula placed 3-4 mm dorsal to MR for the injection of anti-SERT-SAP into MR. Following a 5-7 day period of recovery, hippocampal EEG activity was recorded daily for 7 days as rats freely moved about in a shielded enclose, and then re-assessed under the same conditions following neurotoxic lesions. We found that neurotoxic lesions of MR that resulted in a substantial destruction of 5-HT MR cells (80-90%) produced a continuous theta rhythm in rats; that is, during locomotor behavior as well as during states when theta is normally absent, such as immobility and grooming. For some rats, theta was equivalent during complete immobility and active movement. These results support earlier findings that 5-HT cells of MR are directly involved in the desynchronization of the hippocampal EEG, and indicate that the MR exerts a powerful modulatory influence on the hippocampus.

Related Products: Anti-SERT-SAP (Cat. #IT-23)

Nattie EE, Li A, Richerson GB, Lappi DA (2004) Medullary serotonergic neurons and adjacent neurons that express neurokinin-1 receptors are both involved in chemoreception in vivo. J Physiol 556(1):235-253. doi: 10.1113/jphysiol.2003.059766 PMID: 14724193

Summary: The retrotrapezoid nucleus contains neurokinin-1 receptor (NK-1r)-expressing neurons that are involved in chemoreception. NK-1r-expressing neurons are also present in areas that contain medullary serotonergic neurons. These serotonergic neurons have been shown to be chemosensitive in vitro. With two 100-nl injections of 1 µM SP-SAP (Cat. #IT-07), anti-SERT-SAP (Cat. #IT-23), or both, the authors examined whether both cell populations are involved in chemoreception in vivo in rats. The results support that separate populations of serotonergic and NK-1r-expressing neurons are each involved in chemoreception in vivo.

Related Products: SP-SAP (Cat. #IT-07), Anti-SERT-SAP (Cat. #IT-23), Antibody to Serotonin Transporter (SERT, Cat. #AB-N09)

Richerson GB, Nattie EE, Deneris ES, Lauder JM (2003) Serotonergic neurons and development: implications for normal brain function and human disease. Neuroscience 2003 Abstracts 329. Society for Neuroscience, New Orleans, LA.

Summary: Symposium. Serotonergic neurons have widely divergent projections to virtually all of the CNS, and are involved in a variety of brain functions. This symposium will focus on how dysfunction of 5-HT neurons during development can influence brain function throughout life. G Richerson will discuss pH chemosensitivity of 5-HT neurons, how this changes during development, and the emerging hypothesis that these neurons induce arousal, a feeling of suffocation and hyperventilation in response to increased CO2. E Nattie has used focal manipulations of the raphe in vivo, including cell specific killing with an antibody to the serotonin transporter conjugated to the toxin saporin, to show that dysfunction of 5-HT neurons may lead to a defect in physiologic regulatory processes that are important during development. E Deneris will discuss mutant mice lacking the Pet-1 ETS gene, in which the majority of CNS 5-HT neurons are missing. 25-30% of Pet-1 nulls die during the first postnatal week, which may result from abnormal respiration. Surviving adults display anxiety-like and aggressive behavior. J Lauder will discuss 5-HT as a differentiation signal in prenatal brain development and as a morphogen in craniofacial development. Effects of prenatal exposure to serotonergic drugs or neurotoxins on postnatal outcome will be described. The speakers will introduce new hypotheses about how dysregulation of 5-HT neurons and 5-HT receptors during development may lead to a variety of brain disorders such as SIDS, migraine, autism, panic attacks and anxiety.

Related Products: Anti-SERT-SAP (Cat. #IT-23)

Feldman JL, Mitchell GS, Nattie EE (2003) Breathing: Rhythmicity, Plasticity, Chemosensitivity. Annu Rev Neurosci 26:239-266. doi: 10.1146/annurev.neuro.26.041002.131103

Summary: Recent research has indicated that specific areas of the brain exert control over several aspects of breathing, such as rhythm generation, reaction to hypoxia, and regulation of carbon dioxide levels and pH. This review covers many of the latest advances, some of which utilize SP-SAP (Cat. #IT-07) and anti-SERT-SAP (Cat. #IT-23). The use of these targeted toxins allows altered breathing behavior through elimination of very specific cell populations.

Related Products: SP-SAP (Cat. #IT-07), Anti-SERT-SAP (Cat. #IT-23)

Nattie EE, Li A, Richerson G, Lappi D (2002) Specific killing of rat medullary raphe 5-HT neurons by a serotonin transporter antibody-saporin conjugate reduces the ventilatory response to increased CO2 during sleep and wakefulness. Neuroscience 2002 Abstracts 221.3. Society for Neuroscience, Orlando, FL.

Summary: CO2 increases the firing rate of medullary raphe 5-HT neurons in vitro (Richerson et al., Respir. Physiol. 129: 175-190, 2001) and focal CO2 dialysis in the medullary raphe increases ventilation in the sleeping rat (Nattie and Li, J. Appl. Physiol. 90: 1247-1257, 2001). To examine in vivo the relative importance of these 5-HT neurons in chemoreception we used an antibody to the external ring of the serotonin tranport protein (SERT)(SFN abstract #814.9, 2001) conjugated to the cell toxin saporin (SAP). Rat medullary raphe neurons (P0) in culture assayed by TPOH immunoreactivity were killed by 10 and 5 nM SERT-SAP with peak effects at 4 and 7 days, respectively. Non-serotonergic neurons were unaffected. In adult rats after measurement of baseline ventilatory values, we placed EEG/EMG electrodes and injected the SERT-SAP conjugate (1 uM) into the medullary raphe (two adjacent 100 nl injections). There was substantial loss of TPOH but not NK1R immunoreactivity measured at 14 days. There was no effect on ventilation during air breathing awake or asleep. Ventilation during 7% CO2 was significantly decreased in sleep (P < 0.001; repeated measures ANOVA) at days 1, 3, 7, and 14 (-13 to -15%; P < 0.05; Tukey post-hoc test) and in wakefulness (P < 0.01; repeated measures ANOVA) at days 1, 3, 7, and 14 (-10 to -16%; P < 0.05; Tukey post-hoc test). Medullary raphe serotonergic neurons in the rat play an important role in the ventilatory response to systemic hypercapnia during sleep and wakefulness.

Related Products: Anti-SERT-SAP (Cat. #IT-23)

Lappi D, Kohls M, Majer K, Russell B, Blakely R Richerson G (2002) Targeting serotonin re-uptake transporter (SERT) -expressing cells with a monoclonal antibody to an epitope from the extracellular domain of SERT: Results with a saporin conjugate. FENS 2002 Abstracts 049.7. Federation of European Neuroscience Societies, Paris, France. PMID: 0

Related Products: Antibody to Serotonin Transporter (SERT, Cat. #AB-N09), Anti-SERT-SAP (Cat. #IT-23)