Phosphodiesterase 9A regulates central cGMP and modulates responses to cholinergic and monoaminergic perturbation in vivo.

Cyclic nucleotides are critical regulators of synaptic plasticity and participate in requisite signaling cascades implicated across multiple neurotransmitter systems. Phosphodiesterase 9A (PDE9A) is a high-affinity, cGMP-specific enzyme widely expressed in the rodent central nervous system. In the current study, we observed neuronal staining with antibodies raised against PDE9A protein in human cortex, cerebellum, and subiculum. We have also developed several potent, selective, and brain-penetrant PDE9A inhibitors and used them to probe the function of PDE9A in vivo. Administration of these compounds to animals led to dose-dependent accumulation of cGMP in brain tissue and cerebrospinal fluid, producing a range of biological effects that implied functional significance for PDE9A-regulated cGMP in dopaminergic, cholinergic, and serotonergic neurotransmission and were consistent with the widespread distribution of PDE9A. In vivo effects of PDE9A inhibition included reversal of the respective disruptions of working memory by ketamine, episodic and spatial memory by scopolamine, and auditory gating by amphetamine, as well as potentiation of risperidone-induced improvements in sensorimotor gating and reversal of the stereotypic scratching response to the hallucinogenic 5-hydroxytryptamine 2A agonist mescaline. The results suggested a role for PDE9A in the regulation of monoaminergic circuitry associated with sensory processing and memory. Thus, PDE9A activity regulates neuronal cGMP signaling downstream of multiple neurotransmitter systems, and inhibition of PDE9A may provide therapeutic benefits in psychiatric and neurodegenerative diseases promoted by the dysfunction of these diverse neurotransmitter systems.

Discovery of two clinical histamine H(3) receptor antagonists: trans-N-ethyl-3-fluoro-3-[3-fluoro-4-(pyrrolidinylmethyl)phenyl]cyclobutanecarboxamide (PF-03654746) and trans-3-fluoro-3-[3-fluoro-4-(pyrrolidin-1-ylmethyl)phenyl]-N-(2-methylpropyl)cyclobutanecarboxamide (PF-03654764).

The discovery of two histamine H(3) antagonist clinical candidates is disclosed. The pathway to identification of the two clinical candidates, 6 (PF-03654746) and 7 (PF-03654764) required five hypothesis driven design cycles. The key to success in identifying these clinical candidates was the development of a compound design strategy that leveraged medicinal chemistry knowledge and traditional assays in conjunction with computational and in vitro safety tools. Overall, clinical compounds 6 and 7 exceeded conservative safety margins and possessed optimal pharmacological and pharmacokinetic profiles, thus achieving our initial goal of identifying compounds with fully aligned oral drug attributes, "best-in-class" molecules.

Preclinical pharmacology of the alpha4beta2 nAChR partial agonist varenicline related to effects on reward, mood and cognition.

The pharmacological properties and pharmacokinetic profile of the alpha4beta2 nicotinic acetylcholine receptor (nAChR) partial agonist varenicline provide an advantageous combination of free brain levels and functional potencies at the target receptor that for a large part explain its efficacy as a smoking cessation aid. Since alpha4beta2 and other nAChR subtypes play important roles in mediating central processes that control reward, mood, cognition and attention, there is interest in examining the effects of selective nAChR ligands such as varenicline in preclinical animal models that assess these behaviors. Here we describe results from studies on varenicline's effects in animal models of addiction, depression, cognition and attention and discuss these in the context of recently published preclinical and preliminary clinical studies that collected data on varenicline's effects on mood, cognition and alcohol abuse disorder. Taken together, the preclinical and the limited clinical data show beneficial effects of varenicline, but further clinical studies are needed to evaluate whether the preclinical effects observed in animal models are translatable to the clinic.

2-aryloxy-4-alkylaminopyridines: discovery of novel corticotropin-releasing factor 1 antagonists.

An orally active clinical candidate of corticotropin-releasing factor 1 (CRF 1) antagonist 1 showed a significant positive food effect in dog and human after oral administration. Efforts to address the food effect issue led us to explore and discover compounds in series 2 as orally active CRF 1 receptor antagonists, in which some compounds showed improved physicochemical properties while retaining desired pharmacological properties. Compound 3a (CP-376395) was selected for further development, due not only to its reduced food effects but also its greater efficacy in CNS models. Compound 3a was advanced to the clinic. The synthesis of representative potential candidates and their in vitro, ex vivo, and in vivo data are described.

First-trimester sonography: is the fetus exposed to high levels of acoustic energy?

PURPOSE: As a form of energy, diagnostic ultrasound has bioeffects on living tissues. The thermal index (TI), TIS (TI for soft tissue), TIB (TI for bone), TIC (TI for cranial bone) expresses the potential for rise in temperature at the ultrasound beam's focal point. The mechanical index (MI) indicates the potential for the ultrasound beam to induce inertial cavitation in tissues. The goal of this study was to characterize the acoustic output of clinical ultrasound instruments, as expressed by TI and MI, during routine first-trimester sonographic examinations. METHODS: A prospective observational study was conducted. First-trimester patients were randomly selected from those scheduled for viability scans. An obstetrician collected data. Sonographers were blinded to the data being sought, which included gestational age, duration of the examination, and every variation in the MI and TI during each sonographic examination. RESULTS: A total of 52 first-trimester examinations were evaluated. The mean gestational age was 8.9 +/- 1.9 weeks. The mean duration of the sonographic examinations was 8.1+/- 1.4 minutes. During the examinations, there were 178 MI variations (mean +/- SD, 0.9 +/- 0.3) and 167 TI variations (mean +/- SD, 0.2 +/- 0.1). CONCLUSION: First-trimester sonographic examinations are associated with a negligible rise in TI.

Acoustic output as measured by mechanical and thermal indices during routine obstetric ultrasound examinations.

OBJECTIVE: The purpose of this study was to quantify the acoustic output of clinical ultrasound instruments, as expressed by the thermal index (TI) and mechanical index (MI), during routine obstetric examinations. METHODS: A prospective, observational study was conducted. Sonographers were unaware of the data being sought. Data were collected regarding duration of the examination and specific duration spent at each MI and TI. RESULTS: A total of 11 first-trimester, 14 second-trimester, and 12 third-trimester examinations were evaluated. The mean duration of the first-trimester examination was 8.9 minutes. The mean MI was 0.73 (range, 0.3-1.3), and the mean TI was 0.34 (0.1-1.7). The mean duration of the second-trimester examination was 31.8 minutes. The mean MI was 1.04 (0.5-1.5), and the mean TI was 0.28 (0.1-2.4). The mean duration of the third-trimester examination was 16.3 minutes. The mean MI was 1.06 (0.2-1.5), and the mean TI was 0.32 (0.1-2.4). Statistical significance existed across trimesters with regard to examination durations and MI (P < .001). However, no statistical significance existed in the TI across trimesters. During the third trimester, 3.5% of the examinations had a TI of greater than 1.0. Of these, 2.4% were between 1.0 and 1.49 and 1.1% were greater than 1.5. These changes (of TI > or = 1) were brief (mean +/- SD, 0.17 +/- 0.08 minutes) and were observed during the short periods of color Doppler imaging. CONCLUSIONS: Output levels during routine obstetric ultrasound examinations, as expressed by the MI and TI, are generally low. However, higher output levels, particularly TI levels of greater than 1.5, can be achieved, although they account for only a very small proportion of examination time.