Intranasal aspiration of satratoxin G (SG), a mycotoxin produced by the black mold Stachybotrys chartarum, selectively induces apoptosis in olfactory sensory neurons (OSNs) in mouse olfactory epithelium (OE) through unknown mechanisms. Here, we show a dose-dependent induction of apoptosis 24 h post-SG exposure in vitro as measured by increased activated caspases in the OP6 olfactory placodal cell line and increased propidium iodide staining in primary OE cell cultures. Intranasal aspiration of SG increased TUNEL (Terminal dUTP Nick End Labeling) staining in the neuronal layer of the OE and significantly increased the latency to find a buried food pellet, confirming that SG selectively induces neuronal apoptosis and demonstrating that SG impairs the sense of smell. Next, we investigated whether ATP can prevent SG-induced OE toxicity. ATP did not decrease apoptosis under physiological conditions but significantly reduced SG-induced OSN apoptosis in vivo and in vitro. Furthermore, purinergic receptor inhibition significantly increased apoptosis in OE primary cell culture and in vivo. These data indicate that ATP is neuroprotective against SG-induced OE toxicity. The number of cells that incorporated 5'-bromodeoxyuridine, a measure of proliferation, was significantly increased 3 and 6 days post-SG aspiration. Treatment with purinergic receptor antagonists significantly reduced SG-induced cell proliferation, whereas post-treatment with ATP significantly potentiated SG-induced cell proliferation. These data indicate that ATP is released and promotes cell proliferation via activation of purinergic receptors in SG-induced OE injury. Thus, the purinergic system is a therapeutic target to alleviate or restore the loss of OSNs.

Increased sympathetic nervous system activity contributes to deoxycorticosterone acetate (DOCA)-salt hypertension in rats. ATP and norepinephrine (NE) are coreleased from perivascular sympathetic nerves. NE acts at prejunctional a 2 -adrenergic receptors (a 2 ARs) to inhibit NE release, and a 2 AR function is impaired in DOCA-salt rats. Adenosine, an enzymatic ATP degradation product, acts at prejunctional A 1 adenosine receptors (A 1 Rs) to inhibit NE release. We tested the hypothesis that prejunctional A 1 R function is impaired in sympathetic nerves supplying mesenteric arteries (MAs) and veins (MVs) of DOCAsalt rats. Electrically evoked NE release and constrictions of blood vessels were studied in vitro with use of amperometry to measure NE oxidation currents and video microscopy, respectively. Immunohistochemical methods were used to localize tyrosine hydroxylase (TH) and A 1 Rs in perivascular sympathetic nerves. TH and A 1 Rs colocalized to perivascular sympathetic nerves. Adenosine and N 6 -cyclopentyl-adenosine (CPA, A 1 R agonist) constricted MVs but not MAs. Adenosine and CPA (0.001-10 mM) inhibited neurogenic constrictions and NE release in MAs and MVs. DOCA-salt arteries were resistant to adenosine and CPA-mediated inhibition of NE release and constriction. The A 2A adenosine receptor agonist CGS21680 (C 23 H 29 N 7 O 6 .HCl.xH 2 O) (0.001-0.1 mM) did not alter NE oxidation currents. We conclude that there are prejunctional A 1 Rs in arteries and both pre-and postjunctional A 1 Rs in veins; thus, adenosine selectively constricts the veins. Prejunctional A 1 R function is impaired in arteries, but not veins, from DOCA-salt rats. Sympathetic autoreceptor dysfunction is not specific to a 2 ARs, but there is a more general disruption of prejunctional mechanisms controlling sympathetic neurotransmitter release in DOCA-salt hypertension.

Complications associated with spinal cord injury (SCI) result from unregulated reflexes below the lesion level. Understanding neurotransmission distal to the SCI could improve quality of life by mitigating complications. The long-term impact of SCI on neurovascular transmission is poorly understood, but reduced sympathetic activity below the site of SCI enhances arterial neurotransmission (1). We studied sympathetic neurovascular transmission using a rat model of long-term paraplegia (T2–3) and tetraplegia (C6–7). Sixteen weeks after SCI, T2–3 and C6–7 rats had lower blood pressure (BP) than sham rats (103  ±  2 and 97  ±  4 vs. 117  ±  6 mmHg, P < 0.05). T2–3 rats had tachycardia (410  ±  6 beats/min), and C6–7 rats had bradycardia (299  ±  10 beats/min) compared with intact rats (321  ±  4 beats/min, P < 0.05). Purinergic excitatory junction potentials (EJPs) were measured in mesenteric arteries (MA) using microlectrodes, and norepinephrine (NE) release was measured using amperometry. NE release was similar in all groups, while EJP frequency-response curves from T2–3 and C6–7 rats were left-shifted vs. sham rats. EJPs in T2–3 and C6–7 rats showed facilitation followed by run-down during stimulation trains (10 Hz, 50 stimuli). MA reactivity to exogenous NE and ATP was similar in all rats. In T2–3 and C6–7 rats, NE content was increased in left cardiac ventricles compared with intact rats, but was not changed in MA, kidney, or spleen. Our data indicate that peripheral purinergic, but not adrenergic, neurotransmission increases following SCI via enhanced ATP release from periarterial nerves. Sympathetic BP support is reduced after SCI, but improving neurotransmitter release might maintain cardiovascular stability in individuals living with SCI. NEW & NOTEWORTHY This study revealed increased purinergic, but not noradrenergic, neurotransmission to mesenteric arteries in rats with spinal cord injury (SCI). An increased releasable pool of ATP in periarterial sympathetic nerves may contribute to autonomic dysreflexia following SCI, suggesting that purinergic neurotransmission may be a therapeutic target for maintaining stable blood pressure in individuals living with SCI. The selective increase in ATP release suggests that ATP and norepinephrine may be stored in separate synaptic vesicles in periarterial sympathetic varicosities.

Increased sympathetic nervous system activity contributes to DOCA‐salt hypertension in rats. ATP and norepinephrine (NE) are released from sympathetic nerves. NE acts at prejunctional α2 adrenoceptors to inhibit NE release and prejunctional α2 adrenoceptor function is impaired in DOCA‐salt rats. Adenosine is a product of ATP hydrolysis and adenosine acts at prejunctional A1 adenosine receptors to inhibit NE release. We tested the hypothesis that prejunctional A1 receptor function is impaired in sympathetic nerves associated with mesenteric arteries (MA) and veins (MV) of DOCA‐salt rats. Electrically‐evoked NE release and constrictions of MA and MV were measured in vitro using amperometry and video microscopy, respectively. Adenosine and N6‐cyclopentyl‐adenosine (CPA, A1 receptor agonist) constricted MV but not MA. Adenosine and CPA caused concentration‐dependent (0.001‐10 μM) inhibition of MA constrictions. Adenosine and CPA concentration responses curves (CRCs) in DOCA‐salt MA were right shifted (P<0.05) compared to control MA. CPA inhibited NE release in MA and MV. The CPA CRC in DOCA‐salt MA, but not MV, was right shifted compared to control MA. These data indicate that there are prejunctional A1 receptors in MA and pre and postjunctional A1 receptors in MV. Prejunctional A1 receptor function is impaired in MA, but not MV, from DOCA‐salt rats. These data indicate that prejunctional α2 adrenoceptors are not selectively affected in DOCA‐salt hypertension. There is a more general disruption of prejunctional mechanisms controlling sympathetic neurotransmitter release.