Neuropsychology consultation to identify learning disorders in children and adolescents: a proposal based on lessons learned during the COVID-19 pandemic

Learning disorders are common neurodevelopmental conditions, occurring both idiopathically and in the context of other medical conditions. They are frequently comorbid with other neurodevelopmental and psychiatric conditions. Delayed identification and treatment have been associated with significant negative psychosocial consequences. The need for pediatric neuropsychologists to efficiently screen for learning disorders is likely to increase in the months and years following the COVID-19 pandemic, which has severely disrupted access to educational services, especially for children who also face racial and economic disparities. In this paper, we describe a consultation model that can be used to screen for learning disorders and can be completed using both in-person and telemedicine visits. Implementation may result in earlier intervention for struggling children, increase access to neuropsychological services without increasing wait times for comprehensive evaluations, and provide opportunities for collaborations with other health professionals (e.g., pediatricians, therapists, psychiatrists, and neurologists).

Executive functioning in high-IQ adults with ADHD

BACKGROUND

To examine the association between psychological tests of executive functioning and functional outcomes among high-IQ adults with attention deficit hyperactivity disorder (ADHD).

METHOD

Subjects were high-IQ adults with (n=64) and without ADHD (n=53). Subjects were administered a battery of neuropsychological tests assessing executive functioning.

RESULTS

High-IQ adults with ADHD performed less well than those without ADHD on several psychological tests of executive functioning, including the Wisconsin Card Sorting Test (WCST), Stroop Color and Word Test, Rey-Osterrieth Complex Figure Test (ROCF), California Verbal Learning Test (CVLT) and an auditory continuous performance test (CPT). Test performance in the high-IQ adult ADHD group, however, was average. In the entire sample, performance on several tests of executive functioning including the ROCF and the CVLT were significant predictors of real-world functioning.

CONCLUSIONS

High-IQ adults with ADHD perform less well on tests of executive functioning relative to high-IQ control participants. Performance on several tests of executive functioning was a significant predictor of functioning.

Neurocognitive impairment in unaffected siblings of youth with bipolar disorder

BACKGROUND

There is growing evidence for the familiality of pediatric bipolar disorder (BPD) and its association with impairments on measures of processing speed, verbal learning and 'executive' functions. The current study investigated whether these neurocognitive impairments index the familial risk underlying the diagnosis.

METHOD

Subjects were 170 youth with BPD (mean age 12.3 years), their 118 non-mood-disordered siblings and 79 non-mood-disordered controls. Groups were compared on a battery of neuropsychological tests from the Wechsler Intelligence Scales, the Stroop Color Word Test, the Wisconsin Card Sorting Test (WCST), the Rey-Osterrieth Complex Figure (ROCF), an auditory working memory Continuous Performance Test (CPT) and the California Verbal Learning Test-Children's Version (CVLT-C). Measures were factor analyzed for data reduction purposes. All analyses controlled for age, sex and attention-deficit/hyperactivity disorder (ADHD).

RESULTS

Principal components analyses with a promax rotation yielded three factors reflecting: (1) processing speed/verbal learning, (2) working memory/interference control and (3) abstract problem solving. The CPT working memory measure with interference filtering demands (WM INT) was only administered to subjects aged > or =12 years and was therefore analyzed separately. BPD youth showed impairments versus controls and unaffected relatives on all three factors and on the WM INT. Unaffected relatives exhibited impairments versus controls on the abstract problem-solving factor and the WM INT. They also showed a statistical trend (p=0.07) towards worse performance on the working memory/interference control factor.

CONCLUSIONS

Neurocognitive impairments in executive functions may reflect the familial neurobiological risk mechanisms underlying pediatric BPD and may have utility as endophenotypes in molecular genetic studies of the condition.

Further evidence of association between two NET single-nucleotide polymorphisms with ADHD

The norepinephrine transporter (NET) gene is an attractive candidate gene for attention-deficit hyperactivity disorder (ADHD). Noradrenergic systems are critical to higher brain functions such as attention and executive function, which are defective in ADHD. The clinical efficacy of medications that target NET also supports its role in the etiology of ADHD. Here, we have applied a dense mapping strategy to capture all genetic variations within the NET gene in a large number of ADHD families (474 trios). As a result, we found association of the same alleles from two single-nucleotide polymorphisms (rs3785143 and rs11568324) previously identified in another large-scale ADHD genetic study (International Multisite ADHD Geneproject). Furthermore, the effect sizes were consistent across both studies. This is the first time that identical alleles of NET from different studies were implicated, and thus our report provides further evidence that the NET gene is involved in the etiology of ADHD.

Investigation of variation in SNAP-25 and ADHD and relationship to co-morbid major depressive disorder

Synaptosomal-associated protein of 25 kDa (SNAP-25), a protein involved in presynaptic neurotransmitter release, is a candidate gene for attention deficit/hyperactivity disorder (ADHD). Previous investigators have reported association initially with two single nucleotide polymorphisms (SNPs) (rs3746544, rs1051312) and their associated haplotypes. Subsequently, additional SNPs across the region were also reported to be associated with ADHD. We attempted to replicate these observations in a sample of 229 families with ADHD offspring by genotyping 61 SNPs spanning the region containing SNAP-25. A single SNP (rs3787283) which is in strong linkage disequilibrium (LD) with rs3746544 and rs1051312 (D' = 0.89-0.94) resulted in a nominally significant association (P = 0.002). When we pooled our data with those from prior studies, results were modestly significant for rs3746544 (P = 0.048) and rs6077690 (P = 0.031). As an attempt to determine if specific ADHD-related phenotypes may be more relevant to SNAP-25 than the categorical diagnosis, we carried out exploratory subgroup analysis in our ADHD sample according to co-morbid status. We found the strongest association result in the ADHD patients with co-morbid major depressive disorder (MDD). Six SNPs were nominally associated with the ADHD and co-morbid MDD cases (P = 0.012-0.045). Furthermore, a haplotype block located 11 kb 3' of the gene showed positive evidence for association with this phenotype (global P = 0.013). In conclusion, we report some evidence supporting the association of previously implicated SNPs (rs3746544, rs1051312) of SNAP-25 to ADHD. We further suggest that co-morbidity with MDD may enhance detection of the association between SNAP-25 and ADHD.

Evidence for an Association of the Dopamine D5 Receptor Gene on Age at Onset of Attention Deficit Hyperactivity Disorder

The purpose of this study was to determine whether the single nucleotide polymorphisms (SNPs) within candidate genes for attention deficit hyperactivity disorder (ADHD) are associated with the age at onset for ADHD. One hundred and forty-three SNPs were genotyped across five candidate genes (DRD5, SLC6A3, HTR1B, SNAP25, DRD4) for ADHD in 229 families with at least one affected offspring. SNPs with the highest estimated power to detect an association with age at onset were selected for each candidate gene, using a power-based screening procedure that does not compromise the nominal significance level. A time-to-onset analysis for family-based samples was performed on these SNPs to determine if an association exists with age at onset for ADHD. Seven consecutive SNPs surrounding the D5 dopamine receptor gene (DRD5), were associated with the age at onset for ADHD; FDR adjusted q-values ranged from 0.008 to 0.023. This analysis indicates that individuals with the risk genotype develop ADHD earlier than individuals with any other genotype. A haplotype analysis across the 6 significant SNPs that were in linkage disequilibrium with one another, CTCATA, was also found to be significant (p-value = 0.02). We did not observe significant associations with age at onset for the other candidate loci tested. Although definitive conclusions await independent replication, these results suggest that a variant in DRD5 may affect age at onset for ADHD.

Stability of executive function deficits into young adult years: a prospective longitudinal follow-up study of grown up males with ADHD

OBJECTIVE

Although individuals with attention deficit-hyperactivity disorder (ADHD) commonly exhibit deficits in executive functions that greatly increase the morbidity of the disorder, all available information on the subject is cross sectional.

METHOD

Males (n = 85) 9-22 years with ADHD followed over 7 years into young adulthood were assessed on measures of sustained attention/vigilance, planning and organization, response inhibition, set shifting and categorization, selective attention and visual scanning, verbal and visual learning, and memory. A binary definition of executive function deficits (EFDs) was defined based on a subject manifesting at least two abnormal tests 1.5 standard deviations from controls.

RESULTS

The majority of subjects maintained EFDs over time (kappa: 0.41, P < 0.001; sensitivity: 55%, specificity: 85%, positive predictive value: 69%, and negative predictive value: 75%).

CONCLUSION

Considering the morbidity of EFDs, these findings stress the importance of their early recognition for prevention and early intervention strategies. EFDs are stable over time.

A study of how socioeconomic status moderates the relationship between SNPs encompassing BDNF and ADHD symptom counts in ADHD families

Recent animal research suggests that brain-derived neurotrophic factor (BDNF), may mediate response to different environmental stimuli. In this paper, we evaluated the possible role of BDNF as a moderator of attention deficit hyperactivity disorder (ADHD) in the context of different socioeconomic classes. We genotyped ten single nucleotide polymorphisms (SNPs) in and around BDNF in 229 families and evaluate whether there are SNP-by-socioeconomic status (SES) interactions for attention deficit hyperactivity. We developed three quantitative phenotypes for ADHD from nine inattentive and nine hyperactive-impulsive symptoms that were used in SNP-by-SES interaction analyses using a new methodology implemented in the computer program PBAT. Findings were adjusted for multiple comparisons using the false discovery rate. We found multiple significant SNP-by-SES interactions using the inattentive symptom count. This study suggests that different SES classes may modify the effect of the functional variant(s) in and around BDNF to have an impact on the number of ADHD symptom counts that are observed. The two exons within BDNF represent potential functional variants that may be causing the observed associations.

Learning disabilities and executive dysfunction in boys with attention-deficit/hyperactivity disorder

The effect of comorbid reading or arithmetic learning disabilities (LDs) on neuropsychological function in attention-deficit/hyperactivity disorder (ADHD) was studied. Participants were young males diagnosed with ADHD, with and without LD, and non-ADHD, non-LD male controls of similar age. LD was defined by combined regression-based and low-achievement classifications. Analyses adjusted for the effect of psychiatric comorbidity, age, and socioeconomic status on neuropsychological function. Children who had both ADHD and LD were significantly more impaired on both executive and nonexecutive functions than ADHD children without LD. Neuropsychological performance was most impaired in ADHD with combined arithmetic and reading disability. These data indicate that comorbid LD, especially arithmetic disability, significantly increases the severity of executive function impairment in ADHD.

Long-term stability of the Child Behavior Checklist in a clinical sample of youth with attention deficit hyperactivity disorder

Evaluated the long-term stability of the Child Behavior Checklist (CBCL) in a longitudinal clinical sample of youth with attention deficit hyperactivity disorder (ADHD), testing the hypothesis that the CBCL scales will show stability over time. Participants were 105 Caucasian, non-Hispanic boys with ADHD between the ages of 6 and 17 assessed at baseline and at a 4-year follow-up. Stability of CBCL scales were computed for dimensional (intraclass correlation coefficients [ICCs], Pearson correlations) and dichotomized scale scores (kappa coefficients and odds ratios [ORs]). Evidence was found for stability of the categorical and dimensional types of scores, as demonstrated by statistically significant stability of the Pearson correlation coefficients, kappas, and ORs. The robust findings obtained from ICCs and kappa coefficients document substantial stability for CBCL scales over time within individuals with ADHD. These results support the informativeness of the CBCL as a useful measure of longitudinal course in clinical samples of youth with ADHD.

A family study of psychiatric comorbidity in girls and boys with attention-deficit/hyperactivity disorder

BACKGROUND

Because attention-deficit/hyperactivity disorder (ADHD) is relatively infrequent among girls, little is known about the nature and causes of psychiatric comorbidity in girls and the reason for gender differences in the prevalence of these comorbidities.

METHODS

Using blinded, structured psychiatric interviews, we studied two groups of boys: 140 ADHD probands and 120 non-ADHD comparisons. These groups had 454 and 368 first-degree biological relatives, respectively. We also studied two groups of girls: 140 ADHD probands and 122 non-ADHD comparisons. These groups had 417 and 369 first-degree biological relatives, respectively.

RESULTS

The co-occurrence of ADHD and comorbid psychopathology in families was the same for families ascertained through boy and girl probands.

CONCLUSIONS

Our results suggest that boys and girls do not differ in the familial risk factors that mediate comorbid psychopathology and the familial aggregation of comorbid disorders in ADHD families. Although this is consistent with prior work suggesting more similarities than differences in the nature of psychiatric comorbidity in ADHD boys and girls, we cannot make strong conclusions, owing to the possibility of cohort effects.

Separating attention deficit hyperactivity disorder and learning disabilities in girls: a familial risk analysis

OBJECTIVE

Familial risk analysis was used to clarify the relationship in girls between attention deficit hyperactivity disorder (ADHD) and learning disabilities in either mathematics or reading.

METHOD

The authors assessed the presence of ADHD and learning disabilities in 679 first-degree relatives of three groups of index children: girls with ADHD and a comorbid learning disability, girls with ADHD but no learning disabilities, and a comparison group of girls without ADHD.

RESULTS

The risk for ADHD was similarly higher in families of ADHD probands with and without learning disabilities; both groups had significantly higher rates of ADHD than did families of the comparison girls. In contrast, only among relatives of ADHD probands with a learning disability was there a higher risk for learning disabilities. A strong (although statistically nonsignificant) difference emerged that suggested at least some degree of cosegregation of ADHD and learning disabilities in family members. There was no evidence of nonrandom mating between spouses with ADHD and learning disabilities.

CONCLUSIONS

These results extend previously reported findings regarding the relationship of ADHD and learning disabilities to female subjects and raise the possibility that, in girls, the relationship between ADHD and learning disabilities is due to shared familial risk factors.

Learning disabilities and executive dysfunction in boys with attention-deficit/hyperactivity disorder

The effect of comorbid reading or arithmetic learning disabilities (LDs) on neuropsychological function in attention-deficit/hyperactivity disorder (ADHD) was studied. Participants were young males diagnosed with ADHD, with and without LD, and non-ADHD, non-LD male controls of similar age. LD was defined by combined regression-based and low-achievement classifications. Analyses adjusted for the effect of psychiatric comorbidity, age, and socioeconomic status on neuropsychological function. Children who had both ADHD and LD were significantly more impaired on both executive and nonexecutive functions than ADHD children without LD. Neuropsychological performance was most impaired in ADHD with combined arithmetic and reading disability. These data indicate that comorbid LD, especially arithmetic disability, significantly increases the severity of executive function impairment in ADHD.

Meta-analysis of the association between the 7-repeat allele of the dopamine D(4) receptor gene and attention deficit hyperactivity disorder

OBJECTIVE

Family, twin, and adoption studies show attention deficit hyperactivity disorder (ADHD) to have a substantial genetic component. Although several studies have shown an association between ADHD and the 7-repeat allele of the dopamine D(4) receptor gene (DRD4), several studies have not. Thus, the status of the ADHD-DRD4 association is uncertain.

METHOD

Meta-analysis was applied to case-control and family-based studies of the association between ADHD and DRD4 to assess the joint evidence for the association, the influence of individual studies, and evidence for publication bias.

RESULTS

For both the case-control and family-based studies, the authors found 1) support for the association between ADHD and DRD4, 2) no evidence that this association was accounted for by any one study, and 3) no evidence for publication bias.

CONCLUSIONS

Although the association between ADHD and DRD4 is small, these results suggest that it is real. Further studies are needed to clarify what variant of DRD4 (or some nearby gene) accounts for this association.

Attention-deficit/hyperactivity disorder in adults: an overview

To assess the validity of adult attention-deficit/hyperactivity disorder (ADHD), we reviewed clinical, family, psychopharmacologic, neurobiological, and outcome studies. We found multiple reports describing adults with clinical features highly reminiscent of the childhood ADHD. These adults, who are impulsive, inattentive, and restless, have the clinical "look and feel" of ADHD children. As with their childhood counterparts, many adults with ADHD suffer from antisocial, depressive, and anxiety disorders. They also show clinically significant impairments--histories of school failure, occupational problems, and traffic accidents. Studies of biological features show correspondences between child and adult cases of ADHD. Both show familial aggregation and a characteristic profile of neuropsychologic deficits; an emerging neuroimaging literature suggests that abnormalities in the same brain regions underlie both the child and adult forms of the disorder. Although these converging lines of evidence support the validity of ADHD in adults, follow-up studies of ADHD children have yielded ambiguous results. This ambiguity is in part due to differences in how researchers define the persistence of ADHD, a problem that suggests future research focus on how best to diagnose ADHD in adulthood.

Genetic influences on attention deficit hyperactivity disorder

In this article we review behavioral and molecular genetics studies of attention deficit hyperactivity disorder (ADHD). Family, twin, and adoption studies, along with segregation analyses and molecular genetic studies, all support the hypothesis that both genetic and environmental factors contribute to the etiology of ADHD. Despite this strong evidence for the familial transmission of ADHD, the mode of transmission requires further clarification. In addition, because ADHD appears to be genetically heterogeneous, more work is needed to delineate genetically homogeneous subtypes and describe the range of expression of their underlying genotypes.

Toward a transactional conceptualization of oppositional defiant disorder: implications for assessment and treatment

The conceptualization and treatment of oppositional defiant disorder (ODD) has been characterized by surprising homogeneity. In this paper evidence is presented to underscore the heterogeneity within ODD, including research demonstrating (a) the distinction between reactive and proactive forms of aggression; (b) the importance of affective modulation and self-regulation, and associated cognitive skills, in the development of the skill of compliance; and (c) high levels of comorbidity between ODD and other disorders. The disparate pathways that give rise to oppositional behavior suggest that different children with ODD may require different forms of intervention. The necessity of a transactional conceptualization, of achieving a comprehensive understanding of the factors underlying the difficulties of individual children with ODD, and of matching intervention ingredients to the specific needs of different children and families is discussed.

Comparison of effects of ACE inhibition with calcium channel blockade on renal disease in a model combining genetic hypertension and diabetes

The aim of this study was to compare the renal effects of angiotensin converting enzyme (ACE) inhibition with calcium channel blockade in a model combining genetic hypertension with diabetes. Streptozotocin diabetes was induced in spontaneously hypertensive rats (SHR). The animals were then randomized to receive no treatment, the ACE inhibitor, perindopril, or the dihydropyridine calcium antagonist lacidipine. Body weight, systolic blood pressure, glycemic control, renal function, and albumin excretion rate (AER) were assessed serially over the 32-week study period. At week 32 the animals were killed and glomerular volume was measured. Both antihypertensive regimens significantly reduced systolic blood pressure in diabetic SHR. There was no significant difference in glycemic control, serum creatinine, or glomerular filtration rate among the three groups at week 32. The ACE inhibitor perindopril significantly reduced AER and glomerular hypertrophy over the 32 weeks, whereas the calcium antagonist lacidipine failed to reduce AER or glomerular hypertrophy. Thus, in contrast to the effects of ACE inhibition, calcium channel blockade with lacidipine, despite significantly reducing blood pressure, failed to reduce renal injury in this model. These results support the hypothesis that antihypertensive regimens may differ in their capacity to protect the diabetic kidney, despite similar effects on systemic blood pressure.

The paradoxical effect of diet commercials on reinhibition of dietary restraint

Although many studies have explored the mechanism by which dietary restraint becomes disinhibited, few have examined how restraint is restored or "reinhibited." Using a taste test with preload design, we showed a sad movie clip interrupted by diet-related commercials, neutral commercials, or no commercials to women with high and low restraint scores. We predicted that images of successful dieting would foster reinhibition. Results, however, revealed the opposite: high restrained eaters who viewed the diet-oriented commercials ate more than other subjects. We interpret these data as suggesting that diet-related images act as additional disinhibitors and view our results in light of research linking ego threat to dietary disinhibition (Heatherton, Herman, & Polivy, 1991).

The paradoxical effect of diet commercials on reinhibition of dietary restraint

Although many studies have explored the mechanism by which dietary restraint becomes disinhibited, few have examined how restraint is restored or "reinhibited." Using a taste test with preload design, we showed a sad movie clip interrupted by diet-related commercials, neutral commercials, or no commercials to women with high and low restraint scores. We predicted that images of successful dieting would foster reinhibition. Results, however, revealed the opposite: high restrained eaters who viewed the diet-oriented commercials ate more than other subjects. We interpret these data as suggesting that diet-related images act as additional disinhibitors and view our results in light of research linking ego threat to dietary disinhibition (Heatherton, Herman, & Polivy, 1991).

The effects of perindopril and triple therapy in a normotensive model of diabetic nephropathy

The effect of the angiotensin-converting enzyme inhibitor, perindopril, on functional and structural parameters of diabetic nephropathy has been compared with triple therapy (hydralazine, reserpine, and hydrochlorothiazide) in normotensive, STZ-induced diabetic Sprague-Dawley rats. Animal groups included control rats, diabetic rats treated with perindopril, diabetic rats receiving triple therapy, and untreated diabetic rats. Treatment was continued for 32 wk. Blood pressure reduction and severity of diabetes, as assessed by body weight and glycemic control were similar with both drug regimens. A similar rise in plasma renin activity occurred in the two groups receiving antihypertensive drugs, whereas the perindopril but not the triple therapy group had suppressed plasma angiotensin-converting enzyme activity. No significant difference was observed in renal function among the four groups. Diabetes was associated with a progressive increase in albuminuria, but this rise was ameliorated by both perindopril and triple therapy. No significant difference was noted in albuminuria between triple therapy and perindopril-treated diabetic rats. Diabetes was associated with glomerular basement membrane thickening, mesangial expansion, and glomerular volume. No glomerular ultrastructural parameter was affected by antihypertensive drugs. No specific benefit of angiotensin-converting enzyme inhibition over triple therapy could be detected in this normotensive model of diabetic nephropathy.

A review of the short-term benefits of antihypertensive treatment with emphasis on stroke

Hypertension is the major underlying risk factor for stroke, and the risk of stroke increases proportionally to the rise in blood pressure. In the elderly, systolic hypertension increases the risk of stroke. Stroke in hypertensive patients may be due to Charcot-Bouchard aneurysm, to atherosclerosis of the extracranial and major cerebral arteries, or to embolism as a result of cardiac disease. Reduction of blood pressure greatly reduces the risk of stroke in severe, mild-to-moderate, and isolated systolic hypertension. The reduction in stroke risk occurs up to a year after the onset of treatment and appears to persist thereafter. The use of dihydropyridine calcium antagonists may confer further benefits in addition to those related to blood pressure reduction as these agents block the influx of calcium into ischemic brain cells, thereby limiting the extent of the infarction. However, although these effects have been impressive in experimental models, there is as yet no convincing evidence of this effect in clinical studies.

Angiotensin II, sodium, and cardiovascular hypertrophy in spontaneously hypertensive rats

Angiotensin II (Ang II) may cause cardiovascular hypertrophy as a consequence of increased blood pressure or possibly by direct trophic actions. To dissociate Ang II and blood pressure in young spontaneously hypertensive rats (SHR), we used sodium loading during angiotensin converting enzyme inhibitor treatment. Animals were treated between 6 and 10 weeks of age with perindopril to lower Ang II and blood pressure, or with perindopril and 1% saline drinking fluid or perindopril and aldosterone infusion to lower Ang II but maintain high blood pressure. Blood pressure, heart weight, and media/lumen ratio of mesenteric resistance arteries were studied while rats were on treatment at 10 weeks of age and 15 weeks after treatment at 25 weeks of age. Perindopril lowered blood pressure and inhibited the development of cardiovascular hypertrophy. Saline or aldosterone restored high blood pressure during perindopril treatment and resulted in increased heart weight/body weight and resistance artery media/lumen ratios in direct proportion to the elevation of blood pressure. Because increased structure occurred despite perindopril treatment, we conclude that direct trophic actions of Ang II are not essential for the development of cardiovascular hypertrophy in young SHR and that the antitrophic actions of angiotensin converting enzyme inhibitors depend more on changes in blood pressure than on Ang II. However, restoration of blood pressure and structure by sodium during perindopril treatment raises the possibility that the design of the cardiovascular system and blood pressure may depend indirectly on Ang II through effects on sodium metabolism.

The management of diabetic proteinuria. Which antihypertensive agent?

Diabetic renal disease is a clinical syndrome in which proteinuria is followed by the development of renal failure, and is commonly associated with the concomitant development of hypertension. In insulin-dependent diabetic (IDDM) patients, hypertension often first appears in the microalbuminuric phase of diabetic nephropathy whereas in non-insulin-dependent diabetic (NIDDM) patients, hypertension often antecedes nephropathy and may precede the diagnosis of diabetes. Antihypertensive regimens including diuretics, vasodilators such as hydralazine, beta-blockers and ACE inhibitors reduce proteinuria and delay the decline in renal function in IDDM patients with established nephropathy. No such data are as yet available for calcium antagonists. In microalbuminuric diabetic patients with hypertension, conventional antihypertensive agents, ACE inhibitors and calcium antagonists have been shown to decrease urinary albumin excretion. In the diabetic patient with normal blood pressure and microalbuminuria, there is much less information. It appears likely that ACE inhibitors reduce or retard the rate of increase in albuminuria in these patients. The effect on ultimately delaying or preventing renal failure remains unknown although the preliminary evidence is encouraging. Data on calcium antagonists remain inconclusive with some reports suggesting an increase in proteinuria with the dihydropyridine calcium antagonists. However, a recent longer term study suggested that nifedipine may prevent the rise in albuminuria which is generally observed in the untreated normotensive microalbuminuric subject.

Antihypertensive therapy in a model combining spontaneous hypertension with diabetes

We have compared the effects of the angiotensin converting enzyme inhibitor, perindopril, and a conventional antihypertensive regimen (triple therapy: hydralazine, reserpine and hydrochlorothiazide) on kidney function and albuminuria in hypertensive diabetic rats. Diabetes was induced with streptozotocin in spontaneously hypertensive (SHR) rats and they were randomized to receive no treatment, perindopril or triple therapy. Antihypertensive drugs were commenced at the time of induction of diabetes and continued for 16 weeks. Blood pressure reduction was equal in the groups treated with perindopril or triple therapy. All groups had similar severity of diabetes as determined by body weight, serum glucose and glycated hemoglobin levels. Whereas plasma renin activity rose in both the perindopril and triple therapy groups, it is likely that the effects on angiotensin II levels were opposite since perindopril but not triple therapy was associated with a significant reduction in plasma angiotensin converting enzyme activity. Diabetes was associated with an increase in glomerular filtration rate. At 12 weeks, glomerular filtration rate was higher in the perindopril treated group when compared to the triple therapy group, but neither group treated with antihypertensive therapy was different to untreated diabetic rats. Both drug regimens reduced albuminuria in the diabetic rats to a similar degree apparently independently of their effects on the renin-angiotensin system. Studies in diabetic subjects are warranted to evaluate different classes of antihypertensive drugs with respect to their effects on kidney function, proteinuria and glomerular morphology.

Hypertension and vascular disease

The use of antihypertensive drug treatment has altered the natural history of hypertension. Whereas congestive heart failure, cerebral hemorrhage, and renal failure were the major complications of untreated severe hypertension, myocardial infarction and thrombotic stroke have emerged as the major problems in treated hypertensives. None of the major therapeutic trials in hypertension have provided evidence that reducing blood pressure reduces the risk of atherosclerotic complications of hypertension. Hypertension certainly aggravates the severity of atheromatous lesions in experimental animals and, thus, may do so in humans. However, atherosclerosis is more closely related to disturbances in lipoprotein metabolism than to other factors. The common finding that serum cholesterol is raised in hypertensive patients may be due to atherosclerosis being the primary lesion, with the hypertension as a secondary complication rather than the primary lesion.

Sir Horace Smirk. Pioneer in drug treatment of hypertension

Sir Horace Smirk deserves much of the credit for establishing the benefits of reducing blood pressure. He was one of the main early proponents of the idea that it was the raised intra-arterial pressure itself that caused many of the cardiac and vascular complications of hypertension. His training in both pharmacology and internal medicine enabled him to devise practical methods for successful treatment of hypertension with ganglion blocking drugs such as hexamethonium. The major clinical benefits that followed such drug treatment proved a great stimulus to the development of drugs with fewer disadvantages and to widespread acceptance of the beneficial effects of antihypertensive drug treatment.

Nephropathy in model combining genetic hypertension with experimental diabetes. Enalapril versus hydralazine and metoprolol therapy

We compared the effects of the angiotensin-converting enzyme inhibitor enalapril and a conventional antihypertensive regimen (hydralazine and metoprolol) on kidney function, albuminuria, and glomerular ultrastructure in hypertensive diabetic and nondiabetic rats. Diabetes was induced with streptozocin at 8 wk of age in spontaneously hypertensive (SHR) rats. Antihypertensive drugs were administered in drinking water from the time of induction of diabetes in all groups. Blood pressure reduction was equal in the diabetic and nondiabetic SHR rats receiving either enalapril or hydralazine plus metoprolol. In diabetic SHR rats, there was a rise in serum creatinine after 32 wk, which did not occur in diabetic rats treated with either antihypertensive regimen or in nondiabetic rats. Both drug regimens reduced albuminuria in diabetic and nondiabetic SHR rats to a similar degree. Enalapril and the combination of hydralazine and metoprolol were associated with decreased glomerular basement membrane thickness and glomerular volume in diabetic and nondiabetic SHR rats without significant effect on fractional mesangial volume. Thus, antihypertensive therapy retards the development of albuminuria, glomerular basement membrane thickening, and glomerular hypertrophy in the rat in the presence or absence of diabetes. No specific benefit of angiotensin-converting enzyme inhibition was observed in these hypertensive models of nephropathy. Human studies comparing the effects of different classes of antihypertensive drugs on kidney function, proteinuria, and glomerular morphology are warranted.

Serotonin antagonists and vascular protection

There is very suggestive evidence for a role of serotonin release from platelets in the mechanisms for platelet aggregation, arterial thrombosis, and arterial spasm. These effects are mediated via the 5HT2 receptor and are specifically antagonized by ketanserin. The recently published PACK study was a randomized controlled trial of the effects of ketanserin in patients with intermittent claudication. The purpose of the trial was to discover whether ketanserin treatment would reduce the incidence of atherosclerotic complications such as myocardial infarction or stroke. An unexpected adverse interaction between ketanserin and potassium-losing diuretics was observed, causing an excess of deaths in the group taking this combination of drugs. The "intention-to-treat" analysis showed no overall difference between ketanserin and placebo in terms of cardiovascular complications. Withdrawal of patients taking potassium-losing diuretics left insufficient numbers of patients in the study to answer the original question. However, the "on-treatment" analysis excluding those taking the combination suggested strongly, although did not prove, that ketanserin reduced thrombotic episodes by about 25%. It is concluded that the risks of interactions between many drugs and potassium-losing diuretics make the use of the latter undesirable. Further studies on ketanserin, possibly combined with thromboxane A2 inhibitors, seem highly desirable.

Smoking as a risk factor for cerebral ischaemia

To assess whether a rigorous clinical classification, based on computerised tomography, of patients with cerebral ischaemia would identify subgroups at higher or lower risk with respect to cigarette smoking habits, a case-control study was carried out on 422 cases of first-episode cerebral ischaemia matched for age and sex with 422 community-based neighbourhood controls. Patients with ischaemic stroke due to extracranial or intracranial vascular disease were at higher risk from smoking than has previously been reported for stroke (relative risk 5.7, 95% confidence interval 2.8, 12.0) whereas those with stroke due to cardiac emboli had no excess risk associated with smoking (relative risk 0.4 [0.1, 1.8]). After cessation of smoking, the relative risk declined gradually over 10 years, at the end of which time a significant risk was still evident. This finding may imply that the risk incurred by smoking is due mainly to atheroma formation, rather than transient haematological effects. Exposure to smoking by a spouse was an independent risk factor for the whole group of cerebral ischaemia patients (relative risk 1.7 [1.1, 2.6]), but this was not so for smoking by either parent (relative risk 1.2 [0.8, 1.8]). These findings suggest that smoking is a more potent risk factor for the most common form of ischaemic stroke than has previously been appreciated. The persistent nature of the risk even after cessation of smoking and the possible risk associated with passive exposure strengthens public health arguments against smoking.

Enalapril retards glomerular basement membrane thickening and albuminuria in the diabetic rat

This study has evaluated the effects of the angiotensin converting enzyme inhibitor Enalapril on glomerular ultrastructure and albuminuria in normotensive and hypertensive diabetic rats. Streptozotocin-diabetes was induced in Wistar Kyoto and spontaneously hypertensive rats. Enalapril was administered in drinking water in diabetic normotensive, control hypertensive and diabetic hypertensive rats. Enalapril therapy prevented an increase in glomerular basement membrane thickness in diabetic normotensive, control hypertensive and diabetic hypertensive rats without any significant effect on fractional mesangial volume. Enalapril decreased albuminuria in diabetic normotensive, control hypertensive and diabetic hypertensive rats. Thus, enalapril retards the development of glomerular basement membrane thickening and albuminuria in the rat, in the presence or absence of hypertension.

Effects of genetic hypertension on diabetic nephropathy in the rat--functional and structural characteristics

Streptozotocin (STZ) diabetes was induced in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. Body weight, blood pressure, renal function, glycaemic control and proteinuria were assessed monthly for 32 weeks. At 32 weeks, the animals were killed and glomerular basement membrane (GBM) thickness and fractional mesangial volume were measured. There was no significant difference in renal function between diabetic SHR and diabetic WKY. Diabetic SHR showed an earlier and larger rise in total proteinuria and urinary albumin excretion than diabetic WKY. Urinary albumin excretion was increased more than tenfold in diabetic SHR compared to diabetic WKY after 32 weeks of diabetes. GBM thickness was significantly increased in diabetic SHR compared with diabetic WKY. Both diabetic WKY and diabetic SHR showed mesangial expansion when compared to their nondiabetic counterparts. On the other hand, both hypertensive models showed increased glomerular volume, which was not influenced by the presence of diabetes. The diabetic SHR model has features of accelerated nephropathy, as evidenced by increased albuminuria and GBM thickness. This suggests that pre-existing hypertension may play an important role in the progression of diabetic renal disease.

Does hypertension predispose to coronary disease? Conflicting epidemiological and experimental evidence

Hypertension is associated with an increased risk of coronary events. Treatment of hypertension in controlled trials has not reduced the incidence of coronary events, although the risk of stroke is reduced. In untreated hypertension, about one-half the deaths were due to hypertensive heart failure, whereas myocardial infarction caused 10%-12% of deaths. In treated hypertension, coronary events cause about 40% of deaths. Although in autopsy serious coronary atherosclerosis is commonly found in hypertension, in severe hypertension, dilated coronary vessels free of atheroma were a common finding. No correlation was noted between the height of blood pressure and degree of coronary atherosclerosis. The relationship between coronary disease and hypertension is consistent with an association between them rather than hypertension being a causal factor. The factors that cause acute myocardial infarction may differ from those which predispose to coronary atherosclerosis.

Effects of continuous infusions (10 days) and cessation of infusions of clonidine and rilmenidine (S 3341) on cardiovascular and behavioral parameters of spontaneously hypertensive rats

Clonidine is a centrally acting antihypertensive drug that acts in vivo at both alpha 1- and alpha 2-adrenoceptor sites, whereas rilmenidine (S 3341) is more selective for alpha 2 adrenoceptors. The present study compared the effects of continuous 10-day infusions of clonidine (5 micrograms/kg/hour) with those of rilmenidine (100 micrograms/kg/hour) on various cardiovascular and behavioral parameters in the spontaneously hypertensive rat. The changes in these parameters after cessation of the infusions were also compared. At these rates of infusion, clonidine and rilmenidine produced quantitatively similar reductions in mean arterial pressure (MAP), lability of MAP and cardiovascular responsiveness during normal behaviors such as eating and grooming. Neither drug infusion affected heart rate. The cessation of the clonidine infusion resulted in a "withdrawal" syndrome characterized by prominent rapid eye movement-sleep rebound, and cardiovascular and behavioral disturbances including an increased lability of MAP, exaggerated cardiovascular responses during normal behaviors, tachycardia, and an "opiate abstinence-like" syndrome including head and body shakes. Cessation of rilmenidine infusion resulted in somewhat similar cardiovascular and behavioral disturbances, but unlike clonidine there was a return to normal rapid eye movement sleep without rebound.

Angiotensins II and III prevent captopril-induced renin release in the rat

1. The effects of exogenous angiotensins II and III (50 pmol/min i.v.) on plasma renin release following captopril injection (5 mg/kg, i.v.) were studied in anaesthetized Sprague-Dawley rats, to determine whether angiotensin II blockade is the major mechanism by which captopril induces renin release. 2. Captopril produced a 12-fold increase in plasma renin concentration compared with saline-injected controls. This was completely reversed by pre-infusion of angiotensin II or III. 3. The fall in blood pressure following captopril treatment was also abolished by angiotensins II and III pre-infusion. Noradrenaline pre-infusion (200-800 ng/min, i.v.) also prevented the captopril-induced hypotension but did not alter the rise in plasma renin. 4. Ureteric ligation did not significantly reduce captopril-induced renin release suggesting that acute changes in sodium excretion or delivery of electrolyte to the macula densa were not involved in renin release. 5. These findings suggest that captopril induces renin release by inhibiting angiotensin II feedback control of renin secretion and that angiotensin III may also modulate renin release.

Genetic hypertension accelerates nephropathy in the streptozotocin diabetic rat

To evaluate whether hypertension is a cause or just an association with diabetic renal disease, diabetes was induced in both normotensive Wistar-Kyoto and spontaneously hypertensive rats (WKY and SHR). Animals were assessed monthly for 8 months before sacrifice. When compared to normotensive diabetic rats (WKY-STZ), hypertensive diabetic rats (SHR-STZ) had an earlier and more rapid rise in urinary albumin excretion. In addition, SHR-STZ had increased glomerular basement membrane thickness when compared to WKY-STZ or SHR. In a separate experiment, Enalapril therapy (35 mg/L) was administered in drinking water to WKY-STZ and SHR-STZ. Enalapril significantly reduced blood pressure in both animal groups, and this was associated with a decrease in urinary albumin excretion. The SHR-STZ model has accelerated nephropathy as determined by both functional and structural parameters. Angiotensin-converting enzyme inhibition is associated with a reduction in albuminuria in both hypertensive and normotensive models of diabetic nephropathy.

Genetic co-segregation of renal haemodynamics and blood pressure in the spontaneously hypertensive rat

1. To determine the relevance of renal circulatory abnormalities found in the immature spontaneously hypertensive rat (SHR) to the genetic hypertensive process, glomerular filtration rate and renal blood flow were measured in conscious F2 rats, derived from cross-breeding SHR and normotensive Wistar-Kyoto rats (WKY), at 4, 11 and 16 weeks of age by determining the renal clearances of 51Cr-ethylenediaminetetra-acetate and 125I-hippuran respectively. Plasma renin activity was measured at 11 and 16 weeks of age. 2. Mean arterial pressure, glomerular filtration rate and renal blood flow increased between 4 and 11 weeks of age. Between 11 and 16 weeks the mean glomerular filtration rate and renal blood flow did not alter, although the mean arterial pressure rose significantly. At 11 weeks of age, during the developmental phase of hypertension, a significant negative correlation between mean arterial pressure and both glomerular filtration rate and renal blood flow was noted. However, by 16 weeks when the manifestations of genetic hypertension were more fully expressed, no correlation between mean arterial pressure and renal blood flow or glomerular filtration rate was observed. Plasma renin activity was negatively correlated with both glomerular filtration rate and renal blood flow, but the relationship was stronger at 11 than at 16 weeks of age. 3. These results suggest that the reduction in renal blood flow and glomerular filtration rate, found in immature SHR, is genetically linked to the hypertension and may be of primary pathogenetic importance. It is proposed that the increased renal vascular resistance in these young animals stimulates the rise of systemic arterial pressure which returns renal blood flow and glomerular filtration rate to normal.

The relevance of serotonin antagonism in the treatment of hypertension

The role of serotonin in the pathogenesis of hypertension is not clear. Serotonin is produced by the enterochromaffin cells of the gut; the greater part of this is metabolised in the liver and lungs and nearly all of the remainder is taken up by the platelets. Consequently, circulating levels of serotonin are extremely low. The arterial wall possesses S2-serotonergic receptors, stimulation of which by serotonin leads to vasoconstriction. There are also serotonergic neurons in the central nervous system, particularly in the medulla, which are concerned with the neurogenic control of the circulation. Ketanserin has a high affinity for the S2-receptors, and thus it will antagonise the stimulating effect of serotonin at these receptors. It also has a weaker affinity for alpha 1-adrenoceptors and may act in part by antagonising the pressor effects of norepinephrine, either directly, or indirectly through a link between serotonin S2-receptors and alpha 1-receptors. Experimental evidence suggests that atheromatous lesions lead to increased sensitivity to the vasoconstricting effects of serotonin. This may be due in part to platelet adhesion to areas of endothelial damage, with an associated reduced presence of endothelial relaxing factor. In human hypertension, ketanserin appears to lower blood pressure more effectively in older patients, an effect which may be due to associated atheroma of the aorta and large arteries of these patients. Serotonin antagonism offers a novel approach to the treatment of the hypertensive patient. The increased effectiveness of ketanserin in elderly patients may be of particular importance.(ABSTRACT TRUNCATED AT 250 WORDS)

Rapid eye movement sleep and the associated cardiovascular changes during and after continuous 10-day infusion of clonidine in normotensive rats: comparison with lofexidine and S3341

The centrally acting alpha-adrenoceptor agonists clonidine, lofexidine, and S3341 vary in their selectivity for the alpha 2-adrenoceptor subtype (S3341 greater than clonidine greater than lofexidine). The aim of this study was to examine the frequency and duration of rapid eye movement (REM) sleep episodes, and the cardiovascular changes associated with these episodes, during and after the continuous (10-day) infusion of saline (0.9% wt/vol), clonidine (10 micrograms/kg/h), lofexidine (10 micrograms/kg/h), or S3341 (50 or 100 micrograms/kg/h) in unrestrained, chronically instrumented rats. During a typical 24-h period, the saline infusion animals (n = 4) had 46 +/- 3 REM sleep episodes of 2.4 +/- 0.1 min duration. The majority of these episodes were associated with relatively minor phasic and tonic changes in arterial blood pressure and heart rate. During infusion, the three drugs markedly reduced the cardiovascular and behavioural signs of REM sleep. On cessation of the clonidine and lofexidine infusions, rebound increases (i.e., to values greater than controls) in the frequency and duration of REM sleep episodes were observed. These episodes were associated with markedly exaggerated fluctuations in arterial blood pressure and heart rate. The REM sleep rebound and associated cardiovascular responses were greater during the post-lofexidine infusion phase. A relatively minor rebound increase in total REM sleep time was observed after cessation of the 100-micrograms/kg/h, but not the 50-micrograms/kg/h, infusion rate of S3341. The cardiovascular responses during the REM sleep episodes were mildly exaggerated after cessation of the higher infusion rate of S3341.(ABSTRACT TRUNCATED AT 250 WORDS)

The Australian Therapeutic Trial in Mild Hypertension

In the Australian Therapeutic Trial in Mild Hypertension treated patients had significantly lower cardiovascular mortality and a significantly lower incidence of cerebrovascular complications than patients given placebos. There was, however, no difference in the incidence of nonfatal myocardial infarction or other new manifestations of ischaemic heart disease. Although the evidence of benefit from treatment was clear-cut, the number of cardiovascular complications in the control group was small. This was due to several factors. Patients admitted to the trial had no preceding evidence of cardiovascular complications, the blood pressure fell spontaneously to below 95 mm Hg in almost half the control group, and patients whose blood pressures rose to levels above 110 mm Hg were given treatment, but remained in the placebo group for analysis. In both treated and placebo groups, trial end-points occurred more frequently in persons whose average diastolic blood pressure during the study remained raised. Ischaemic heart disease and many cases of stroke are due to atherosclerotic arterial disease. This appears not to be favourably influenced by antihypertensive drug therapy.

Persistent effects on blood pressure and renal haemodynamics following chronic angiotensin converting enzyme inhibition with perindopril

Spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats aged 4 and 16 weeks were given an acute oral dose of either Perindopril (3 mg/kg) or vehicle. Direct blood pressure (BP), glomerular filtration rate (GFR) and renal blood flow (RBF) were measured, and renal vascular resistance (RVR) calculated. GFR and RBF were lower in vehicle-treated SHR than WKY at 4 weeks of age, but were not different at 16 weeks. Acute Perindopril increased GFR and RBF and reduced RVR in both strains at both 4 and 16 weeks. Total body sodium, sodium intake and blood pressure were measured in SHR and WKY from 1 to 28 weeks of age. Rats of both strains were treated daily between 4 and 16 weeks of age with either Perindopril (3 mg/kg per day) or vehicle. Chronic Perindopril treatment prevented the development of hypertension in the SHR. From 16 to 28 weeks of age, after stopping Perindopril, BP rose slowly in SHR, but remained lower than vehicle-treated SHR. No changes in total body sodium occurred during Perindopril treatment. GFR and RBF were measured in SHR and WKY chronically treated with either Perindopril or vehicle, 3 days or 12 weeks after stopping treatment. In WKY, GFR and RBF were not different between Perindopril-treated and untreated rats at either measurement. In SHR, GFR and RBF remained significantly higher in rats previously treated with Perindopril at both ages. These findings suggest that renal haemodynamic abnormalities may be important in the initiation of hypertension in the SHR. These renal circulatory abnormalities and the hypertension of the SHR depend, at least in part, on intact converting enzyme activity, yet appear to be independent of abnormalities of total body sodium. At a later age, hypertension seems to develop independently of renal vascular abnormalities.

Renal haemodynamics and total body sodium in immature spontaneously hypertensive and Wistar-Kyoto rats

We have investigated the renal haemodynamics and sodium metabolism in spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats during the first 10 weeks of life. Using constant infusion clearance measurements of 51Cr-EDTA and 125I-hippuran in unrestrained, conscious, 4-week-old rats we found a significant reduction in glomerular filtration rate (GFR) and renal blood flow (RBF), respectively, in SHR compared with WKY. The arterial blood pressure (BP) and renal vascular resistance were also significantly elevated in SHR at this age. Acute oral treatment with hydralazine increased SHR GFR and RBF to equal that of WKY, but acute angiotensin converting enzyme inhibition with oral MK 421 caused the GFR and RBF of SHR to exceed that of WKY. In addition, the plasma renin activity of 4-week-old SHR was significantly elevated compared with WKY. Total body sodium was measured from 1 to 10 weeks of age by determining the whole-body radioactivity of rats equilibrated on 22Na-labelled NaCl of constant specific activity. Indirect blood pressure and sodium intake were measured from weeks 4 to 10 inclusive. Relative sodium retention was observed in SHR both before and during the early developmental phase of hypertension. The sodium intake and BP of SHR were consistently higher than WKY throughout weeks 4 to 10. We propose that increased renal vascular resistance in immature SHR alters the pressure natriuresis relationship to cause sodium retention, with the subsequent development of hypertension.

Evaluation of verapamil in the treatment of hypertension

Two separate randomized double-blind, crossover trials were carried out in hypertensive patients to evaluate the antihypertensive efficacy and safety of verapamil. In the first study, verapamil, in doses of 120 mg three times daily, was compared with pindolol, in doses of 7.5 mg twice daily. A thiazide diuretic was given with both drugs. In another study, verapamil, in doses of 160 mg twice daily, was compared with 200 mg twice daily of labetalol in hypertensive patients with coexisting chronic obstructive lung disease. Blood pressure fell equally with these drugs, and neither of the drugs caused significant side effects. Labetalol significantly reduced both forced expiration volume at 1s (FEV1) and forced vital capacity (FVC), suggesting a bronchoconstrictor effect. Verapamil was devoid of any such effect. Verapamil did not affect plasma renin concentration.