R15 is a large identified neuron present in the abdominal ganglion of the mollusc Aplysia. Previous studies have indicated that this neuron may play a role in water balance and possibly renovascular functions. A peptidic factor contained in the neuron R15 has been shown to increase the water content of Aplysia. To determine the structure of the peptides contained in R15, we purified the extract...

The purpose of this study was to determine the synaptic actions of the bursting peptidergic neuron R15 in Aplysia. R15 is known to be excited by the neuroendocrine bag cells, which trigger egg laying. In the two companion papers, we show that R15 mediates some of the effects of the bag cells on respiratory and reproductive organs. In this paper, we demonstrate that R15 excites L7, a multimodal ...

The purpose of the study described in this and the following two companion papers was to determine the synaptic actions of neuron R15, an endogenously bursting neurosecretory cell in Aplysia, as a step toward determining its physiological function. The results described in this paper demonstrate that activity in R15 increases the frequency of bursting in the R25/L25 network that triggers respir...

Release of the neuropeptide egg-laying hormone (ELH) from Aplysia bag cell neurons augments the endogenous bursting pacemaker activity of neuron R15. We have studied the ionic mechanisms underlying the effect of ELH in voltage-clamped R15 neurons. Both electrical discharge of the bag cells, which releases endogenous ELH, and application of synthetic ELH on cell R15 result in an increase in two ...

Splice-variant products of the R15 neuropeptide gene are differentially expressed within the CNS of Aplysia. The goal of this study was to test whether the neurons in the abdominal ganglion that express the peptides encoded by this gene are part of a common circuit. Expression of R15 peptides had been demonstrated previously in neuron R15. Using a combination of immunocytochemical and analytica...

The effects of the adenylate cyclase inhibitor GDPßS on the response of Aplysia neuron R15 to serotonin (51-IT) were investigated. Previous studies have demonstrated that 5HT causes an increase in K+ conductance in R15 and that the response is mediated by cAMP. At concentrations in the micromolar range, GDPßS inhibits the stimulation ofadenylate cyclase by 5HT in particulate fractions from Aply...

(1) The neuron R15 in the parietovisceral ganglion of Aplysia has a circadian rhythm of spiking activity when recorded in the isolated ganglion. The rhythm is entrained in vivo by light-dark cycles. (2) The phase of the R15 rhythm is a function not only of the entraining light schedule, but also of the time of dissection. Changes in the dissection time during the light portion of the light-dark...

The effects of the adenylate cyclase inhibitor GDP beta S on the response of Aplysia neuron R15 to serotonin (5HT) were investigated. Previous studies have demonstrated that 5HT causes an increase in K+ conductance in R15 and that the response is mediated by cAMP. At concentrations in the micromolar range, GDP beta S inhibits the stimulation of adenylate cyclase by 5HT in particulate fractions ...

Three homologous spectrin domains have remarkably different folding characteristics. We have previously shown that the slow-folding R16 and R17 spectrin domains can be altered to resemble the fast folding R15, in terms of speed of folding (and unfolding), landscape roughness and folding mechanism, simply by substituting five residues in the core. Here we show that, by contrast, R15 cannot be en...