Adolescent morphine exposure changes the endogenous vlPAG opioid response to inflammatory pain in rats.

Adolescence is one of the most critical periods for brain development, and exposure to morphine during this period can have long-life effects on pain-related behaviors. The opioid system in the periaqueductal gray (PAG) is highly vulnerable to drug exposure. However, the impact of adolescent morphine exposure (AME) on the endogenous opioid system in the PAG is currently unknown. This study aims to investigate the long-lasting effects of AME on the endogenous opioid system and its involvement in altering nociceptive behaviors. Adolescent rats were given escalating doses of morphine (2.5-25 mg/kg, subcutaneous) or an equal volume of saline twice daily for 10 consecutive days (PND 31-40). After a 30-day washout period, adult rats underwent formalin tests following microinjection of morphine, naloxone, or saline into the ventrolateral PAG (vlPAG) region. The results indicated that morphine microinjection into the vlPAG of the adolescent morphine-treated group significantly reduced the nociceptive score. However, the analgesic response to morphine in this group was significantly lower compared to the saline-treated group during adolescence. Additionally, the nociceptive score significantly increased following naloxone but not saline microinjection into the vlPAG of the saline-treated group during adolescence, rather than the morphine-treated one. These findings indicate that AME has long-lasting effects on the endogenous opioid system in the vlPAG, which can consequently alter behaviors related to inflammatory pain in adulthood.

Doppler ultrasonography can be used to evaluate the arterial blood supply of hip joints in skeletally immature cats.

OBJECTIVE: To investigate hemodynamics and morphology of hip joint vasculature in cats with the use of color and pulsed-wave Doppler ultrasonography. ANIMALS: 30 client-owned healthy skeletally immature cats presented for routine examinations between September 7, 2022, and March 25, 2023. METHODS: Cats between 3.5 to 18 months old with healthy hip joints and Hct within reference ranges (26% to 44.2%) were eligible for inclusion. Color and pulsed-wave Doppler ultrasonography was performed without sedation. Peak systolic velocity (PSV), mean diastolic velocity (MDV), resistance index (RI), and pulsatility index (PI) were measured for major arteries of the hip joints. RESULTS: Intermediate pulsatility, resistance to flow, and pandiastolic anterograde flow were evident for all arteries evaluated for each joint except for the ligamentum capitis ossis femoris artery (LCOFA). Spectral waveforms for the LCOFA showed a low-resistance pattern with continuous forward diastolic flow. No significant differences were found in the mean PI or MDV between the left and right sides for the ascending branch of the lateral circumflex femoral artery or in the mean PI of the ascending branch of the medial circumflex femoral artery. Mean PSV of the LCOFA was lower (but nonsignificantly) for left hip joints vs right hip joints, whereas other values were often higher on cats' left side vs their right. CLINICAL RELEVANCE: This study provided insight into the morphology and hemodynamics of the femoral head vasculature in skeletally immature cats and showed Doppler ultrasound values to study the clinically normal blood supply to hip joints in cats.

Adolescent morphine exposure increases nociceptive behaviors in rat model of formalin test.

The number of adolescents who use illicit drugs has increased dramatically. Adolescence is a critical period for brain development and maturation. The importance of the study of pain perception and the possible mechanisms involved is crystal clear. Up until now, there has been no evidence regarding the long-term effect of adolescence morphine administration on pain perception. The objective of the present study was to investigate long-lasting effect of adolescent morphine exposure on pain perception as well as analgesic response to a single dose of morphine injection. Adolescent and adult rats received morphine or saline, and then after 30 days of washout period, formalin test was performed. To evaluate morphine analgesia, in a separate group of animals, formalin test was performed after injection of a single dose of morphine during adulthood. The results demonstrated that the adolescent rats treated by morphine exhibited higher pain-related behaviors compared to the control group, while the same results were not observed in adult rats that had been treated by morphine. Moreover, there was no significant difference in analgesic response to a single dose of morphine between two experimental groups. This study demonstrates enduring effect of morphine exposure during adolescence on pain perception.

Exposure to opiates in male adolescent rats alters pain perception in the male offspring.

During the past decades, the use/misuse of opioids has increased dramatically among adolescent population. It is now well acknowledged that various morphological and physiological changes occur in the brain during adolescence. During this critical period, brain development and maturation could be affected by several factors including stress, drug abuse, nutritional status, etc. Although studies on transgenerational effects of substances such as alcohol, nicotine, and cocaine have focused on both paternal and maternal drug exposure, most reports on transgenerational effects of morphine are restricted to maternal exposure. Thus, in this study, we aimed to investigate the transgenerational effect of paternal morphine exposure during adolescence on pain perception and antinociceptive effect of morphine in rat offspring. Male rats received escalating doses of morphine for 10 days during postnatal days 31-40. Twenty days after the last morphine injection, male rats were mated with intact female rats, and then behavioral tests were conducted on the male offspring on postnatal day 60. Pain perception and morphine antinociception were evaluated using the formalin test. Our results demonstrated that morphine-sired and saline-sired animals differed in the interphase and phase 2 of the formalin test. These findings indicate a significant transgenerational effect of paternal morphine exposure on pain-related behaviors in rat offspring.

Analgesic tolerance induced by repeated morphine injections induces cross-tolerance to the analgesic effect of orexin-A in rats.

Repeated administration of morphine or orexin-A produces tolerance to their antinociceptive effects. We investigated the possible incidence of cross-tolerance between orexin-A and morphine. Adult male Sprague-Dawley rats (200-250 g) were used. Under deep anesthesia, a stereotaxic apparatus was used to implant a 23 G cannula into the lateral ventricle for an intracerebroventricular (ICV) microinjection. The antinociceptive effect of three different doses of orexin-A (5, 20, and 40 µM; dissolved in 5 µl sterile saline; ICV) was examined using the hot-plate test at 15, 30, 60, and 90 min after infusion. To evaluate tolerance, orexin-A (20 µM; ICV) or morphine (10 mg/kg; intraperitoneal) was administered for 7 consecutive days (twice per day) and the analgesic response was assessed at days 1, 4, and 7. Cross-tolerance was investigated at day 8 with a single injection of morphine (10 mg/kg; intraperitoneal) to the repeated orexin-A group and a single microinjection of orexin-A (20 µM; ICV) to the repeated morphine group. Analgesic responses were then examined. Administration of both orexin-A and morphine produced significant antinociception at day 1 (P<0.001 compared with the saline group). However, a significant reduction in the analgesic effects of both morphine and orexin-A appeared at day 7, following repeated administration (P<0.01). Orexin-A microinjection at day 8 in the repeated morphine group did not result in significant antinociception (P>0.05), whereas morphine injection in the repeated orexin-A group at day 8 showed a significant analgesic effect (P<0.001). These results indicate cross-tolerance to the analgesic effect of orexin-A following morphine tolerance.

Human Urine Proteomics: Analytical Techniques and Clinical Applications in Renal Diseases.

Urine has been in the center of attention among scientists of clinical proteomics in the past decade, because it is valuable source of proteins and peptides with a relative stable composition and easy to collect in large and repeated quantities with a noninvasive procedure. In this review, we discuss technical aspects of urinary proteomics in detail, including sample preparation, proteomic technologies, and their advantage and disadvantages. Several recent experiments are presented which applied urinary proteome for biomarker discovery in renal diseases including diabetic nephropathy, immunoglobulin A (IgA) nephropathy, focal segmental glomerulosclerosis, lupus nephritis, membranous nephropathy, and acute kidney injury. In addition, several available databases in urinary proteomics are also briefly introduced.

Repeated injections of orexin-A developed behavioral tolerance to its analgesic effects in rats.

OBJECTIVES: Reduction of pharmacological effectiveness or tolerance appears following repeated administration of many analgesic drugs. We investigated tolerance to anti-nociceptive effects of orexin-A, an endogenous potent analgesic peptide using the hot-plate test. MATERIALS AND METHODS: Orexin-A was microinjected ICV (intracerebroventricular) with an interval of 12 hr for 7 continuous days and its anti-nociceptive responses were measured on days 1, 4 and 7 using the hot-plate test following the first day of administration. Orexin-A was used at a dose of 100 pmol to induce analgesic effects. RESULTS: ICV administration of orexin-A produced an effective anti-nociception on the first day of experiment as measured by hot-plate 5, 15, and 30 min after the injection, in comparison with both baselines (hot-plate test one day before the beginning of orexin-A administration and control, saline-administrated group). However, repeated administration of orexin-A on the following days revealed a significant reduction in this analgesic effect during day 4 to day 7. However, to rule out any associative tolerance resulting from learning related to experimental procedures and/or environmental cues, a single injection of orexin-A was administrated to animals of control group (which were receiving saline during 7 days of experiments) and the analgesic effect was observed. CONCLUSION: These results, for the first time, indicated the appearance of tolerance to anti-nociceptive effects of orexin-A, following repeated administrations of this agent.